Fixes for metaclass syntax

IPython/core/formatters.py

@@ -1,655 +1,654 b''
 # -*- coding: utf-8 -*-
 """Display formatters.
 
 Inheritance diagram:
 
 .. inheritance-diagram:: IPython.core.formatters
    :parts: 3
 
 Authors:
 
 * Robert Kern
 * Brian Granger
 """
 #-----------------------------------------------------------------------------
 # Copyright (C) 2010-2011, IPython Development Team.
 #
 # Distributed under the terms of the Modified BSD License.
 #
 # The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 # Stdlib imports
 import abc
 import sys
 import warnings
 # We must use StringIO, as cStringIO doesn't handle unicode properly.
 from io import StringIO
 
 # Our own imports
 from IPython.config.configurable import Configurable
 from IPython.lib import pretty
 from IPython.utils.traitlets import (
     Bool, Dict, Integer, Unicode, CUnicode, ObjectName, List,
 )
-from IPython.utils.py3compat import unicode_to_str
+from IPython.utils.py3compat import unicode_to_str, with_metaclass
 
 
 #-----------------------------------------------------------------------------
 # The main DisplayFormatter class
 #-----------------------------------------------------------------------------
 
 
 class DisplayFormatter(Configurable):
 
     # When set to true only the default plain text formatter will be used.
     plain_text_only = Bool(False, config=True)
     def _plain_text_only_changed(self, name, old, new):
         warnings.warn("""DisplayFormatter.plain_text_only is deprecated.
         
         Use DisplayFormatter.active_types = ['text/plain']
         for the same effect.
         """, DeprecationWarning)
         if new:
             self.active_types = ['text/plain']
         else:
             self.active_types = self.format_types
     
     active_types = List(Unicode, config=True,
         help="""List of currently active mime-types to display.
         You can use this to set a white-list for formats to display.
         
         Most users will not need to change this value.
         """)
     def _active_types_default(self):
         return self.format_types
     
     def _active_types_changed(self, name, old, new):
         for key, formatter in self.formatters.items():
             if key in new:
                 formatter.enabled = True
             else:
                 formatter.enabled = False
     
     # A dict of formatter whose keys are format types (MIME types) and whose
     # values are subclasses of BaseFormatter.
     formatters = Dict()
     def _formatters_default(self):
         """Activate the default formatters."""
         formatter_classes = [
             PlainTextFormatter,
             HTMLFormatter,
             SVGFormatter,
             PNGFormatter,
             JPEGFormatter,
             LatexFormatter,
             JSONFormatter,
             JavascriptFormatter
         ]
         d = {}
         for cls in formatter_classes:
             f = cls(parent=self)
             d[f.format_type] = f
         return d
 
     def format(self, obj, include=None, exclude=None):
         """Return a format data dict for an object.
 
         By default all format types will be computed.
 
         The following MIME types are currently implemented:
 
         * text/plain
         * text/html
         * text/latex
         * application/json
         * application/javascript
         * image/png
         * image/jpeg
         * image/svg+xml
 
         Parameters
         ----------
         obj : object
             The Python object whose format data will be computed.
         include : list or tuple, optional
             A list of format type strings (MIME types) to include in the
             format data dict. If this is set *only* the format types included
             in this list will be computed.
         exclude : list or tuple, optional
             A list of format type string (MIME types) to exclude in the format
             data dict. If this is set all format types will be computed,
             except for those included in this argument.
 
         Returns
         -------
         (format_dict, metadata_dict) : tuple of two dicts
         
             format_dict is a dictionary of key/value pairs, one of each format that was
             generated for the object. The keys are the format types, which
             will usually be MIME type strings and the values and JSON'able
             data structure containing the raw data for the representation in
             that format.
             
             metadata_dict is a dictionary of metadata about each mime-type output.
             Its keys will be a strict subset of the keys in format_dict.
         """
         format_dict = {}
         md_dict = {}
 
         for format_type, formatter in self.formatters.items():
             if include and format_type not in include:
                 continue
             if exclude and format_type in exclude:
                 continue
             
             md = None
             try:
                 data = formatter(obj)
             except:
                 # FIXME: log the exception
                 raise
             
             # formatters can return raw data or (data, metadata)
             if isinstance(data, tuple) and len(data) == 2:
                 data, md = data
             
             if data is not None:
                 format_dict[format_type] = data
             if md is not None:
                 md_dict[format_type] = md
             
         return format_dict, md_dict
 
     @property
     def format_types(self):
         """Return the format types (MIME types) of the active formatters."""
         return self.formatters.keys()
 
 
 #-----------------------------------------------------------------------------
 # Formatters for specific format types (text, html, svg, etc.)
 #-----------------------------------------------------------------------------
 
 
-class FormatterABC(object):
+class FormatterABC(with_metaclass(abc.ABCMeta, object)):
     """ Abstract base class for Formatters.
 
     A formatter is a callable class that is responsible for computing the
     raw format data for a particular format type (MIME type). For example,
     an HTML formatter would have a format type of `text/html` and would return
     the HTML representation of the object when called.
     """
-    __metaclass__ = abc.ABCMeta
 
     # The format type of the data returned, usually a MIME type.
     format_type = 'text/plain'
 
     # Is the formatter enabled...
     enabled = True
 
     @abc.abstractmethod
     def __call__(self, obj):
         """Return a JSON'able representation of the object.
 
         If the object cannot be formatted by this formatter, then return None
         """
         try:
             return repr(obj)
         except TypeError:
             return None
 
 
 class BaseFormatter(Configurable):
     """A base formatter class that is configurable.
 
     This formatter should usually be used as the base class of all formatters.
     It is a traited :class:`Configurable` class and includes an extensible
     API for users to determine how their objects are formatted. The following
     logic is used to find a function to format an given object.
 
     1. The object is introspected to see if it has a method with the name
        :attr:`print_method`. If is does, that object is passed to that method
        for formatting.
     2. If no print method is found, three internal dictionaries are consulted
        to find print method: :attr:`singleton_printers`, :attr:`type_printers`
        and :attr:`deferred_printers`.
 
     Users should use these dictionaries to register functions that will be
     used to compute the format data for their objects (if those objects don't
     have the special print methods). The easiest way of using these
     dictionaries is through the :meth:`for_type` and :meth:`for_type_by_name`
     methods.
 
     If no function/callable is found to compute the format data, ``None`` is
     returned and this format type is not used.
     """
 
     format_type = Unicode('text/plain')
 
     enabled = Bool(True, config=True)
 
     print_method = ObjectName('__repr__')
 
     # The singleton printers.
     # Maps the IDs of the builtin singleton objects to the format functions.
     singleton_printers = Dict(config=True)
     def _singleton_printers_default(self):
         return {}
 
     # The type-specific printers.
     # Map type objects to the format functions.
     type_printers = Dict(config=True)
     def _type_printers_default(self):
         return {}
 
     # The deferred-import type-specific printers.
     # Map (modulename, classname) pairs to the format functions.
     deferred_printers = Dict(config=True)
     def _deferred_printers_default(self):
         return {}
 
     def __call__(self, obj):
         """Compute the format for an object."""
         if self.enabled:
             obj_id = id(obj)
             try:
                 obj_class = getattr(obj, '__class__', None) or type(obj)
                 # First try to find registered singleton printers for the type.
                 try:
                     printer = self.singleton_printers[obj_id]
                 except (TypeError, KeyError):
                     pass
                 else:
                     return printer(obj)
                 # Next look for type_printers.
                 for cls in pretty._get_mro(obj_class):
                     if cls in self.type_printers:
                         return self.type_printers[cls](obj)
                     else:
                         printer = self._in_deferred_types(cls)
                         if printer is not None:
                             return printer(obj)
                 # Finally look for special method names.
                 if hasattr(obj_class, self.print_method):
                     printer = getattr(obj_class, self.print_method)
                     return printer(obj)
                 return None
             except Exception:
                 pass
         else:
             return None
 
     def for_type(self, typ, func):
         """Add a format function for a given type.
 
         Parameters
         -----------
         typ : class
             The class of the object that will be formatted using `func`.
         func : callable
             The callable that will be called to compute the format data. The
             call signature of this function is simple, it must take the
             object to be formatted and return the raw data for the given
             format. Subclasses may use a different call signature for the
             `func` argument.
         """
         oldfunc = self.type_printers.get(typ, None)
         if func is not None:
             # To support easy restoration of old printers, we need to ignore
             # Nones.
             self.type_printers[typ] = func
         return oldfunc
 
     def for_type_by_name(self, type_module, type_name, func):
         """Add a format function for a type specified by the full dotted
         module and name of the type, rather than the type of the object.
 
         Parameters
         ----------
         type_module : str
             The full dotted name of the module the type is defined in, like
             ``numpy``.
         type_name : str
             The name of the type (the class name), like ``dtype``
         func : callable
             The callable that will be called to compute the format data. The
             call signature of this function is simple, it must take the
             object to be formatted and return the raw data for the given
             format. Subclasses may use a different call signature for the
             `func` argument.
         """
         key = (type_module, type_name)
         oldfunc = self.deferred_printers.get(key, None)
         if func is not None:
             # To support easy restoration of old printers, we need to ignore
             # Nones.
             self.deferred_printers[key] = func
         return oldfunc
 
     def _in_deferred_types(self, cls):
         """
         Check if the given class is specified in the deferred type registry.
 
         Returns the printer from the registry if it exists, and None if the
         class is not in the registry. Successful matches will be moved to the
         regular type registry for future use.
         """
         mod = getattr(cls, '__module__', None)
         name = getattr(cls, '__name__', None)
         key = (mod, name)
         printer = None
         if key in self.deferred_printers:
             # Move the printer over to the regular registry.
             printer = self.deferred_printers.pop(key)
             self.type_printers[cls] = printer
         return printer
 
 
 class PlainTextFormatter(BaseFormatter):
     """The default pretty-printer.
 
     This uses :mod:`IPython.lib.pretty` to compute the format data of
     the object. If the object cannot be pretty printed, :func:`repr` is used.
     See the documentation of :mod:`IPython.lib.pretty` for details on
     how to write pretty printers.  Here is a simple example::
 
         def dtype_pprinter(obj, p, cycle):
             if cycle:
                 return p.text('dtype(...)')
             if hasattr(obj, 'fields'):
                 if obj.fields is None:
                     p.text(repr(obj))
                 else:
                     p.begin_group(7, 'dtype([')
                     for i, field in enumerate(obj.descr):
                         if i > 0:
                             p.text(',')
                             p.breakable()
                         p.pretty(field)
                     p.end_group(7, '])')
     """
 
     # The format type of data returned.
     format_type = Unicode('text/plain')
 
     # This subclass ignores this attribute as it always need to return
     # something.
     enabled = Bool(True, config=False)
 
     # Look for a _repr_pretty_ methods to use for pretty printing.
     print_method = ObjectName('_repr_pretty_')
 
     # Whether to pretty-print or not.
     pprint = Bool(True, config=True)
 
     # Whether to be verbose or not.
     verbose = Bool(False, config=True)
 
     # The maximum width.
     max_width = Integer(79, config=True)
 
     # The newline character.
     newline = Unicode('\n', config=True)
 
     # format-string for pprinting floats
     float_format = Unicode('%r')
     # setter for float precision, either int or direct format-string
     float_precision = CUnicode('', config=True)
 
     def _float_precision_changed(self, name, old, new):
         """float_precision changed, set float_format accordingly.
 
         float_precision can be set by int or str.
         This will set float_format, after interpreting input.
         If numpy has been imported, numpy print precision will also be set.
 
         integer `n` sets format to '%.nf', otherwise, format set directly.
 
         An empty string returns to defaults (repr for float, 8 for numpy).
 
         This parameter can be set via the '%precision' magic.
         """
 
         if '%' in new:
             # got explicit format string
             fmt = new
             try:
                 fmt%3.14159
             except Exception:
                 raise ValueError("Precision must be int or format string, not %r"%new)
         elif new:
             # otherwise, should be an int
             try:
                 i = int(new)
                 assert i >= 0
             except ValueError:
                 raise ValueError("Precision must be int or format string, not %r"%new)
             except AssertionError:
                 raise ValueError("int precision must be non-negative, not %r"%i)
 
             fmt = '%%.%if'%i
             if 'numpy' in sys.modules:
                 # set numpy precision if it has been imported
                 import numpy
                 numpy.set_printoptions(precision=i)
         else:
             # default back to repr
             fmt = '%r'
             if 'numpy' in sys.modules:
                 import numpy
                 # numpy default is 8
                 numpy.set_printoptions(precision=8)
         self.float_format = fmt
 
     # Use the default pretty printers from IPython.lib.pretty.
     def _singleton_printers_default(self):
         return pretty._singleton_pprinters.copy()
 
     def _type_printers_default(self):
         d = pretty._type_pprinters.copy()
         d[float] = lambda obj,p,cycle: p.text(self.float_format%obj)
         return d
 
     def _deferred_printers_default(self):
         return pretty._deferred_type_pprinters.copy()
 
     #### FormatterABC interface ####
 
     def __call__(self, obj):
         """Compute the pretty representation of the object."""
         if not self.pprint:
             try:
                 return repr(obj)
             except TypeError:
                 return ''
         else:
             # This uses use StringIO, as cStringIO doesn't handle unicode.
             stream = StringIO()
             # self.newline.encode() is a quick fix for issue gh-597. We need to
             # ensure that stream does not get a mix of unicode and bytestrings,
             # or it will cause trouble.
             printer = pretty.RepresentationPrinter(stream, self.verbose,
                 self.max_width, unicode_to_str(self.newline),
                 singleton_pprinters=self.singleton_printers,
                 type_pprinters=self.type_printers,
                 deferred_pprinters=self.deferred_printers)
             printer.pretty(obj)
             printer.flush()
             return stream.getvalue()
 
 
 class HTMLFormatter(BaseFormatter):
     """An HTML formatter.
 
     To define the callables that compute the HTML representation of your
     objects, define a :meth:`_repr_html_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
 
     The return value of this formatter should be a valid HTML snippet that
     could be injected into an existing DOM. It should *not* include the
     ```<html>`` or ```<body>`` tags.
     """
     format_type = Unicode('text/html')
 
     print_method = ObjectName('_repr_html_')
 
 
 class SVGFormatter(BaseFormatter):
     """An SVG formatter.
 
     To define the callables that compute the SVG representation of your
     objects, define a :meth:`_repr_svg_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
 
     The return value of this formatter should be valid SVG enclosed in
     ```<svg>``` tags, that could be injected into an existing DOM. It should
     *not* include the ```<html>`` or ```<body>`` tags.
     """
     format_type = Unicode('image/svg+xml')
 
     print_method = ObjectName('_repr_svg_')
 
 
 class PNGFormatter(BaseFormatter):
     """A PNG formatter.
 
     To define the callables that compute the PNG representation of your
     objects, define a :meth:`_repr_png_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
 
     The return value of this formatter should be raw PNG data, *not*
     base64 encoded.
     """
     format_type = Unicode('image/png')
 
     print_method = ObjectName('_repr_png_')
 
 
 class JPEGFormatter(BaseFormatter):
     """A JPEG formatter.
 
     To define the callables that compute the JPEG representation of your
     objects, define a :meth:`_repr_jpeg_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
 
     The return value of this formatter should be raw JPEG data, *not*
     base64 encoded.
     """
     format_type = Unicode('image/jpeg')
 
     print_method = ObjectName('_repr_jpeg_')
 
 
 class LatexFormatter(BaseFormatter):
     """A LaTeX formatter.
 
     To define the callables that compute the LaTeX representation of your
     objects, define a :meth:`_repr_latex_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
 
     The return value of this formatter should be a valid LaTeX equation,
     enclosed in either ```$```, ```$$``` or another LaTeX equation
     environment.
     """
     format_type = Unicode('text/latex')
 
     print_method = ObjectName('_repr_latex_')
 
 
 class JSONFormatter(BaseFormatter):
     """A JSON string formatter.
 
     To define the callables that compute the JSON string representation of
     your objects, define a :meth:`_repr_json_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
 
     The return value of this formatter should be a valid JSON string.
     """
     format_type = Unicode('application/json')
 
     print_method = ObjectName('_repr_json_')
 
 
 class JavascriptFormatter(BaseFormatter):
     """A Javascript formatter.
 
     To define the callables that compute the Javascript representation of
     your objects, define a :meth:`_repr_javascript_` method or use the
     :meth:`for_type` or :meth:`for_type_by_name` methods to register functions
     that handle this.
 
     The return value of this formatter should be valid Javascript code and
     should *not* be enclosed in ```<script>``` tags.
     """
     format_type = Unicode('application/javascript')
 
     print_method = ObjectName('_repr_javascript_')
 
 FormatterABC.register(BaseFormatter)
 FormatterABC.register(PlainTextFormatter)
 FormatterABC.register(HTMLFormatter)
 FormatterABC.register(SVGFormatter)
 FormatterABC.register(PNGFormatter)
 FormatterABC.register(JPEGFormatter)
 FormatterABC.register(LatexFormatter)
 FormatterABC.register(JSONFormatter)
 FormatterABC.register(JavascriptFormatter)
 
 
 def format_display_data(obj, include=None, exclude=None):
     """Return a format data dict for an object.
 
     By default all format types will be computed.
 
     The following MIME types are currently implemented:
 
     * text/plain
     * text/html
     * text/latex
     * application/json
     * application/javascript
     * image/png
     * image/jpeg
     * image/svg+xml
 
     Parameters
     ----------
     obj : object
         The Python object whose format data will be computed.
 
     Returns
     -------
     format_dict : dict
         A dictionary of key/value pairs, one or each format that was
         generated for the object. The keys are the format types, which
         will usually be MIME type strings and the values and JSON'able
         data structure containing the raw data for the representation in
         that format.
     include : list or tuple, optional
         A list of format type strings (MIME types) to include in the
         format data dict. If this is set *only* the format types included
         in this list will be computed.
     exclude : list or tuple, optional
         A list of format type string (MIME types) to exclue in the format
         data dict. If this is set all format types will be computed,
         except for those included in this argument.
     """
     from IPython.core.interactiveshell import InteractiveShell
 
     InteractiveShell.instance().display_formatter.format(
         obj,
         include,
         exclude
     )
 

IPython/core/inputtransformer.py

@@ -1,531 +1,531 b''
 import abc
 import functools
 import re
 from io import StringIO
 
 from IPython.core.splitinput import LineInfo
 from IPython.utils import tokenize2
 from IPython.utils.openpy import cookie_comment_re
+from IPython.utils.py3compat import with_metaclass
 from IPython.utils.tokenize2 import generate_tokens, untokenize, TokenError
 
 #-----------------------------------------------------------------------------
 # Globals
 #-----------------------------------------------------------------------------
 
 # The escape sequences that define the syntax transformations IPython will
 # apply to user input.  These can NOT be just changed here: many regular
 # expressions and other parts of the code may use their hardcoded values, and
 # for all intents and purposes they constitute the 'IPython syntax', so they
 # should be considered fixed.
 
 ESC_SHELL  = '!'     # Send line to underlying system shell
 ESC_SH_CAP = '!!'    # Send line to system shell and capture output
 ESC_HELP   = '?'     # Find information about object
 ESC_HELP2  = '??'    # Find extra-detailed information about object
 ESC_MAGIC  = '%'     # Call magic function
 ESC_MAGIC2 = '%%'    # Call cell-magic function
 ESC_QUOTE  = ','     # Split args on whitespace, quote each as string and call
 ESC_QUOTE2 = ';'     # Quote all args as a single string, call
 ESC_PAREN  = '/'     # Call first argument with rest of line as arguments
 
 ESC_SEQUENCES = [ESC_SHELL, ESC_SH_CAP, ESC_HELP ,\
                  ESC_HELP2, ESC_MAGIC, ESC_MAGIC2,\
                  ESC_QUOTE, ESC_QUOTE2, ESC_PAREN ]
 
 
-class InputTransformer(object):
+class InputTransformer(with_metaclass(abc.ABCMeta, object)):
     """Abstract base class for line-based input transformers."""
-    __metaclass__ = abc.ABCMeta
     
     @abc.abstractmethod
     def push(self, line):
         """Send a line of input to the transformer, returning the transformed
         input or None if the transformer is waiting for more input.
         
         Must be overridden by subclasses.
         """
         pass
     
     @abc.abstractmethod
     def reset(self):
         """Return, transformed any lines that the transformer has accumulated,
         and reset its internal state.
         
         Must be overridden by subclasses.
         """
         pass
     
     @classmethod
     def wrap(cls, func):
         """Can be used by subclasses as a decorator, to return a factory that
         will allow instantiation with the decorated object.
         """
         @functools.wraps(func)
         def transformer_factory(**kwargs):
             return cls(func, **kwargs)
         
         return transformer_factory
 
 class StatelessInputTransformer(InputTransformer):
     """Wrapper for a stateless input transformer implemented as a function."""
     def __init__(self, func):
         self.func = func
     
     def __repr__(self):
         return "StatelessInputTransformer(func={0!r})".format(self.func)
     
     def push(self, line):
         """Send a line of input to the transformer, returning the
         transformed input."""
         return self.func(line)
     
     def reset(self):
         """No-op - exists for compatibility."""
         pass
 
 class CoroutineInputTransformer(InputTransformer):
     """Wrapper for an input transformer implemented as a coroutine."""
     def __init__(self, coro, **kwargs):
         # Prime it
         self.coro = coro(**kwargs)
         next(self.coro)
     
     def __repr__(self):
         return "CoroutineInputTransformer(coro={0!r})".format(self.coro)
     
     def push(self, line):
         """Send a line of input to the transformer, returning the
         transformed input or None if the transformer is waiting for more
         input.
         """
         return self.coro.send(line)
     
     def reset(self):
         """Return, transformed any lines that the transformer has
         accumulated, and reset its internal state.
         """
         return self.coro.send(None)
 
 class TokenInputTransformer(InputTransformer):
     """Wrapper for a token-based input transformer.
     
     func should accept a list of tokens (5-tuples, see tokenize docs), and
     return an iterable which can be passed to tokenize.untokenize().
     """
     def __init__(self, func):
         self.func = func
         self.current_line = ""
         self.line_used = False
         self.reset_tokenizer()
     
     def reset_tokenizer(self):
         self.tokenizer = generate_tokens(self.get_line)
     
     def get_line(self):
         if self.line_used:
             raise TokenError
         self.line_used = True
         return self.current_line
     
     def push(self, line):
         self.current_line += line + "\n"
         if self.current_line.isspace():
             return self.reset()
         
         self.line_used = False
         tokens = []
         stop_at_NL = False
         try:
             for intok in self.tokenizer:
                 tokens.append(intok)
                 t = intok[0]
                 if t == tokenize2.NEWLINE or (stop_at_NL and t == tokenize2.NL):
                     # Stop before we try to pull a line we don't have yet
                     break
                 elif t == tokenize2.ERRORTOKEN:
                     stop_at_NL = True
         except TokenError:
             # Multi-line statement - stop and try again with the next line
             self.reset_tokenizer()
             return None
         
         return self.output(tokens)
     
     def output(self, tokens):
         self.current_line = ""
         self.reset_tokenizer()
         return untokenize(self.func(tokens)).rstrip('\n')
     
     def reset(self):
         l = self.current_line
         self.current_line = ""
         self.reset_tokenizer()
         if l:
             return l.rstrip('\n')
 
 class assemble_python_lines(TokenInputTransformer):
     def __init__(self):
         super(assemble_python_lines, self).__init__(None)
     
     def output(self, tokens):
         return self.reset()
 
 @CoroutineInputTransformer.wrap
 def assemble_logical_lines():
     """Join lines following explicit line continuations (\)"""
     line = ''
     while True:
         line = (yield line)
         if not line or line.isspace():
             continue
         
         parts = []
         while line is not None:
             if line.endswith('\\') and (not has_comment(line)):
                 parts.append(line[:-1])
                 line = (yield None) # Get another line
             else:
                 parts.append(line)
                 break
         
         # Output
         line = ''.join(parts)
 
 # Utilities
 def _make_help_call(target, esc, lspace, next_input=None):
     """Prepares a pinfo(2)/psearch call from a target name and the escape
     (i.e. ? or ??)"""
     method  = 'pinfo2' if esc == '??' \
                 else 'psearch' if '*' in target \
                 else 'pinfo'
     arg = " ".join([method, target])
     if next_input is None:
         return '%sget_ipython().magic(%r)' % (lspace, arg)
     else:
         return '%sget_ipython().set_next_input(%r);get_ipython().magic(%r)' % \
            (lspace, next_input, arg)
     
 # These define the transformations for the different escape characters.
 def _tr_system(line_info):
     "Translate lines escaped with: !"
     cmd = line_info.line.lstrip().lstrip(ESC_SHELL)
     return '%sget_ipython().system(%r)' % (line_info.pre, cmd)
 
 def _tr_system2(line_info):
     "Translate lines escaped with: !!"
     cmd = line_info.line.lstrip()[2:]
     return '%sget_ipython().getoutput(%r)' % (line_info.pre, cmd)
 
 def _tr_help(line_info):
     "Translate lines escaped with: ?/??"
     # A naked help line should just fire the intro help screen
     if not line_info.line[1:]:
         return 'get_ipython().show_usage()'
 
     return _make_help_call(line_info.ifun, line_info.esc, line_info.pre)
 
 def _tr_magic(line_info):
     "Translate lines escaped with: %"
     tpl = '%sget_ipython().magic(%r)'
     if line_info.line.startswith(ESC_MAGIC2):
         return line_info.line
     cmd = ' '.join([line_info.ifun, line_info.the_rest]).strip()
     return tpl % (line_info.pre, cmd)
 
 def _tr_quote(line_info):
     "Translate lines escaped with: ,"
     return '%s%s("%s")' % (line_info.pre, line_info.ifun,
                          '", "'.join(line_info.the_rest.split()) )
 
 def _tr_quote2(line_info):
     "Translate lines escaped with: ;"
     return '%s%s("%s")' % (line_info.pre, line_info.ifun,
                            line_info.the_rest)
 
 def _tr_paren(line_info):
     "Translate lines escaped with: /"
     return '%s%s(%s)' % (line_info.pre, line_info.ifun,
                          ", ".join(line_info.the_rest.split()))
 
 tr = { ESC_SHELL  : _tr_system,
        ESC_SH_CAP : _tr_system2,
        ESC_HELP   : _tr_help,
        ESC_HELP2  : _tr_help,
        ESC_MAGIC  : _tr_magic,
        ESC_QUOTE  : _tr_quote,
        ESC_QUOTE2 : _tr_quote2,
        ESC_PAREN  : _tr_paren }
 
 @StatelessInputTransformer.wrap
 def escaped_commands(line):
     """Transform escaped commands - %magic, !system, ?help + various autocalls.
     """
     if not line or line.isspace():
         return line
     lineinf = LineInfo(line)
     if lineinf.esc not in tr:
         return line
     
     return tr[lineinf.esc](lineinf)
 
 _initial_space_re = re.compile(r'\s*')
 
 _help_end_re = re.compile(r"""(%{0,2}
                               [a-zA-Z_*][\w*]*        # Variable name
                               (\.[a-zA-Z_*][\w*]*)*   # .etc.etc
                               )
                               (\?\??)$                # ? or ??
                               """,
                               re.VERBOSE)
 
 # Extra pseudotokens for multiline strings and data structures
 _MULTILINE_STRING = object()
 _MULTILINE_STRUCTURE = object()
 
 def _line_tokens(line):
     """Helper for has_comment and ends_in_comment_or_string."""
     readline = StringIO(line).readline
     toktypes = set()
     try:
         for t in generate_tokens(readline):
             toktypes.add(t[0])
     except TokenError as e:
         # There are only two cases where a TokenError is raised.
         if 'multi-line string' in e.args[0]:
             toktypes.add(_MULTILINE_STRING)
         else:
             toktypes.add(_MULTILINE_STRUCTURE)
     return toktypes
 
 def has_comment(src):
     """Indicate whether an input line has (i.e. ends in, or is) a comment.
 
     This uses tokenize, so it can distinguish comments from # inside strings.
 
     Parameters
     ----------
     src : string
       A single line input string.
 
     Returns
     -------
     comment : bool
         True if source has a comment.
     """
     return (tokenize2.COMMENT in _line_tokens(src))
 
 def ends_in_comment_or_string(src):
     """Indicates whether or not an input line ends in a comment or within
     a multiline string.
     
     Parameters
     ----------
     src : string
       A single line input string.
 
     Returns
     -------
     comment : bool
         True if source ends in a comment or multiline string.
     """
     toktypes = _line_tokens(src)
     return (tokenize2.COMMENT in toktypes) or (_MULTILINE_STRING in toktypes)
         
 
 @StatelessInputTransformer.wrap
 def help_end(line):
     """Translate lines with ?/?? at the end"""
     m = _help_end_re.search(line)
     if m is None or ends_in_comment_or_string(line):
         return line
     target = m.group(1)
     esc = m.group(3)
     lspace = _initial_space_re.match(line).group(0)
 
     # If we're mid-command, put it back on the next prompt for the user.
     next_input = line.rstrip('?') if line.strip() != m.group(0) else None
 
     return _make_help_call(target, esc, lspace, next_input)
 
 
 @CoroutineInputTransformer.wrap
 def cellmagic(end_on_blank_line=False):
     """Captures & transforms cell magics.
     
     After a cell magic is started, this stores up any lines it gets until it is
     reset (sent None).
     """
     tpl = 'get_ipython().run_cell_magic(%r, %r, %r)'
     cellmagic_help_re = re.compile('%%\w+\?')
     line = ''
     while True:
         line = (yield line)
         # consume leading empty lines
         while not line:
             line = (yield line)
         
         if not line.startswith(ESC_MAGIC2):
             # This isn't a cell magic, idle waiting for reset then start over
             while line is not None:
                 line = (yield line)
             continue
         
         if cellmagic_help_re.match(line):
             # This case will be handled by help_end
             continue
         
         first = line
         body = []
         line = (yield None)
         while (line is not None) and \
                                 ((line.strip() != '') or not end_on_blank_line):
             body.append(line)
             line = (yield None)
         
         # Output
         magic_name, _, first = first.partition(' ')
         magic_name = magic_name.lstrip(ESC_MAGIC2)
         line = tpl % (magic_name, first, u'\n'.join(body))
 
 
 def _strip_prompts(prompt_re, initial_re=None):
     """Remove matching input prompts from a block of input.
     
     Parameters
     ----------
     prompt_re : regular expression
         A regular expression matching any input prompt (including continuation)
     initial_re : regular expression, optional
         A regular expression matching only the initial prompt, but not continuation.
         If no initial expression is given, prompt_re will be used everywhere.
         Used mainly for plain Python prompts, where the continuation prompt
         ``...`` is a valid Python expression in Python 3, so shouldn't be stripped.
     
     If initial_re and prompt_re differ,
     only initial_re will be tested against the first line.
     If any prompt is found on the first two lines,
     prompts will be stripped from the rest of the block.
     """
     if initial_re is None:
         initial_re = prompt_re
     line = ''
     while True:
         line = (yield line)
         
         # First line of cell
         if line is None:
             continue
         out, n1 = initial_re.subn('', line, count=1)
         line = (yield out)
         
         if line is None:
             continue
         # check for any prompt on the second line of the cell,
         # because people often copy from just after the first prompt,
         # so we might not see it in the first line.
         out, n2 = prompt_re.subn('', line, count=1)
         line = (yield out)
         
         if n1 or n2:
             # Found a prompt in the first two lines - check for it in
             # the rest of the cell as well.
             while line is not None:
                 line = (yield prompt_re.sub('', line, count=1))
         
         else:
             # Prompts not in input - wait for reset
             while line is not None:
                 line = (yield line)
 
 @CoroutineInputTransformer.wrap
 def classic_prompt():
     """Strip the >>>/... prompts of the Python interactive shell."""
     # FIXME: non-capturing version (?:...) usable?
     prompt_re = re.compile(r'^(>>> ?|\.\.\. ?)')
     initial_re = re.compile(r'^(>>> ?)')
     return _strip_prompts(prompt_re, initial_re)
 
 @CoroutineInputTransformer.wrap
 def ipy_prompt():
     """Strip IPython's In [1]:/...: prompts."""
     # FIXME: non-capturing version (?:...) usable?
     # FIXME: r'^(In \[\d+\]: | {3}\.{3,}: )' clearer?
     prompt_re = re.compile(r'^(In \[\d+\]: |\ \ \ \.\.\.+: )')
     return _strip_prompts(prompt_re)
 
 
 @CoroutineInputTransformer.wrap
 def leading_indent():
     """Remove leading indentation.
     
     If the first line starts with a spaces or tabs, the same whitespace will be
     removed from each following line until it is reset.
     """
     space_re = re.compile(r'^[ \t]+')
     line = ''
     while True:
         line = (yield line)
         
         if line is None:
             continue
         
         m = space_re.match(line)
         if m:
             space = m.group(0)
             while line is not None:
                 if line.startswith(space):
                     line = line[len(space):]
                 line = (yield line)
         else:
             # No leading spaces - wait for reset
             while line is not None:
                 line = (yield line)
 
 
 @CoroutineInputTransformer.wrap
 def strip_encoding_cookie():
     """Remove encoding comment if found in first two lines
     
     If the first or second line has the `# coding: utf-8` comment,
     it will be removed.
     """
     line = ''
     while True:
         line = (yield line)
         # check comment on first two lines
         for i in range(2):
             if line is None:
                 break
             if cookie_comment_re.match(line):
                 line = (yield "")
             else:
                 line = (yield line)
         
         # no-op on the rest of the cell
         while line is not None:
             line = (yield line)
 
 
 assign_system_re = re.compile(r'(?P<lhs>(\s*)([\w\.]+)((\s*,\s*[\w\.]+)*))'
                               r'\s*=\s*!\s*(?P<cmd>.*)')
 assign_system_template = '%s = get_ipython().getoutput(%r)'
 @StatelessInputTransformer.wrap
 def assign_from_system(line):
     """Transform assignment from system commands (e.g. files = !ls)"""
     m = assign_system_re.match(line)
     if m is None:
         return line
     
     return assign_system_template % m.group('lhs', 'cmd')
 
 assign_magic_re = re.compile(r'(?P<lhs>(\s*)([\w\.]+)((\s*,\s*[\w\.]+)*))'
                              r'\s*=\s*%\s*(?P<cmd>.*)')
 assign_magic_template = '%s = get_ipython().magic(%r)'
 @StatelessInputTransformer.wrap
 def assign_from_magic(line):
     """Transform assignment from magic commands (e.g. a = %who_ls)"""
     m = assign_magic_re.match(line)
     if m is None:
         return line
     
     return assign_magic_template % m.group('lhs', 'cmd')

IPython/core/interactiveshell.py

@@ -1,3164 +1,3164 b''
 # -*- coding: utf-8 -*-
 """Main IPython class."""
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2001 Janko Hauser <[e-mail]>
 #  Copyright (C) 2001-2007 Fernando Perez. <[e-mail]>
 #  Copyright (C) 2008-2011  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 from __future__ import absolute_import
 from __future__ import print_function
 
 import __future__
 import abc
 import ast
 import atexit
 import functools
 import os
 import re
 import runpy
 import sys
 import tempfile
 import types
 import subprocess
 from io import open as io_open
 
 from IPython.config.configurable import SingletonConfigurable
 from IPython.core import debugger, oinspect
 from IPython.core import magic
 from IPython.core import page
 from IPython.core import prefilter
 from IPython.core import shadowns
 from IPython.core import ultratb
 from IPython.core.alias import AliasManager, AliasError
 from IPython.core.autocall import ExitAutocall
 from IPython.core.builtin_trap import BuiltinTrap
 from IPython.core.compilerop import CachingCompiler, check_linecache_ipython
 from IPython.core.display_trap import DisplayTrap
 from IPython.core.displayhook import DisplayHook
 from IPython.core.displaypub import DisplayPublisher
 from IPython.core.error import UsageError
 from IPython.core.extensions import ExtensionManager
 from IPython.core.formatters import DisplayFormatter
 from IPython.core.history import HistoryManager
 from IPython.core.inputsplitter import IPythonInputSplitter, ESC_MAGIC, ESC_MAGIC2
 from IPython.core.logger import Logger
 from IPython.core.macro import Macro
 from IPython.core.payload import PayloadManager
 from IPython.core.prefilter import PrefilterManager
 from IPython.core.profiledir import ProfileDir
 from IPython.core.prompts import PromptManager
 from IPython.lib.latextools import LaTeXTool
 from IPython.testing.skipdoctest import skip_doctest
 from IPython.utils import PyColorize
 from IPython.utils import io
 from IPython.utils import py3compat
 from IPython.utils import openpy
 from IPython.utils.decorators import undoc
 from IPython.utils.io import ask_yes_no
 from IPython.utils.ipstruct import Struct
 from IPython.utils.path import get_home_dir, get_ipython_dir, get_py_filename, unquote_filename
 from IPython.utils.pickleshare import PickleShareDB
 from IPython.utils.process import system, getoutput
-from IPython.utils.py3compat import builtin_mod, unicode_type, string_types
+from IPython.utils.py3compat import (builtin_mod, unicode_type, string_types,
+                                     with_metaclass)
 from IPython.utils.strdispatch import StrDispatch
 from IPython.utils.syspathcontext import prepended_to_syspath
 from IPython.utils.text import (format_screen, LSString, SList,
                                 DollarFormatter)
 from IPython.utils.traitlets import (Integer, CBool, CaselessStrEnum, Enum,
                                      List, Unicode, Instance, Type)
 from IPython.utils.warn import warn, error
 import IPython.core.hooks
 
 #-----------------------------------------------------------------------------
 # Globals
 #-----------------------------------------------------------------------------
 
 # compiled regexps for autoindent management
 dedent_re = re.compile(r'^\s+raise|^\s+return|^\s+pass')
 
 #-----------------------------------------------------------------------------
 # Utilities
 #-----------------------------------------------------------------------------
 
 @undoc
 def softspace(file, newvalue):
     """Copied from code.py, to remove the dependency"""
 
     oldvalue = 0
     try:
         oldvalue = file.softspace
     except AttributeError:
         pass
     try:
         file.softspace = newvalue
     except (AttributeError, TypeError):
         # "attribute-less object" or "read-only attributes"
         pass
     return oldvalue
 
 @undoc
 def no_op(*a, **kw): pass
 
 @undoc
 class NoOpContext(object):
     def __enter__(self): pass
     def __exit__(self, type, value, traceback): pass
 no_op_context = NoOpContext()
 
 class SpaceInInput(Exception): pass
 
 @undoc
 class Bunch: pass
 
 
 def get_default_colors():
     if sys.platform=='darwin':
         return "LightBG"
     elif os.name=='nt':
         return 'Linux'
     else:
         return 'Linux'
 
 
 class SeparateUnicode(Unicode):
     """A Unicode subclass to validate separate_in, separate_out, etc.
 
     This is a Unicode based trait that converts '0'->'' and '\\n'->'\n'.
     """
 
     def validate(self, obj, value):
         if value == '0': value = ''
         value = value.replace('\\n','\n')
         return super(SeparateUnicode, self).validate(obj, value)
 
 
 class ReadlineNoRecord(object):
     """Context manager to execute some code, then reload readline history
     so that interactive input to the code doesn't appear when pressing up."""
     def __init__(self, shell):
         self.shell = shell
         self._nested_level = 0
 
     def __enter__(self):
         if self._nested_level == 0:
             try:
                 self.orig_length = self.current_length()
                 self.readline_tail = self.get_readline_tail()
             except (AttributeError, IndexError):   # Can fail with pyreadline
                 self.orig_length, self.readline_tail = 999999, []
         self._nested_level += 1
 
     def __exit__(self, type, value, traceback):
         self._nested_level -= 1
         if self._nested_level == 0:
             # Try clipping the end if it's got longer
             try:
                 e = self.current_length() - self.orig_length
                 if e > 0:
                     for _ in range(e):
                         self.shell.readline.remove_history_item(self.orig_length)
 
                 # If it still doesn't match, just reload readline history.
                 if self.current_length() != self.orig_length \
                     or self.get_readline_tail() != self.readline_tail:
                     self.shell.refill_readline_hist()
             except (AttributeError, IndexError):
                 pass
         # Returning False will cause exceptions to propagate
         return False
 
     def current_length(self):
         return self.shell.readline.get_current_history_length()
 
     def get_readline_tail(self, n=10):
         """Get the last n items in readline history."""
         end = self.shell.readline.get_current_history_length() + 1
         start = max(end-n, 1)
         ghi = self.shell.readline.get_history_item
         return [ghi(x) for x in range(start, end)]
 
 
 @undoc
 class DummyMod(object):
     """A dummy module used for IPython's interactive module when
     a namespace must be assigned to the module's __dict__."""
     pass
 
 #-----------------------------------------------------------------------------
 # Main IPython class
 #-----------------------------------------------------------------------------
 
 class InteractiveShell(SingletonConfigurable):
     """An enhanced, interactive shell for Python."""
 
     _instance = None
     
     ast_transformers = List([], config=True, help=
         """
         A list of ast.NodeTransformer subclass instances, which will be applied
         to user input before code is run.
         """
     )
 
     autocall = Enum((0,1,2), default_value=0, config=True, help=
         """
         Make IPython automatically call any callable object even if you didn't
         type explicit parentheses. For example, 'str 43' becomes 'str(43)'
         automatically. The value can be '0' to disable the feature, '1' for
         'smart' autocall, where it is not applied if there are no more
         arguments on the line, and '2' for 'full' autocall, where all callable
         objects are automatically called (even if no arguments are present).
         """
     )
     # TODO: remove all autoindent logic and put into frontends.
     # We can't do this yet because even runlines uses the autoindent.
     autoindent = CBool(True, config=True, help=
         """
         Autoindent IPython code entered interactively.
         """
     )
     automagic = CBool(True, config=True, help=
         """
         Enable magic commands to be called without the leading %.
         """
     )
     cache_size = Integer(1000, config=True, help=
         """
         Set the size of the output cache.  The default is 1000, you can
         change it permanently in your config file.  Setting it to 0 completely
         disables the caching system, and the minimum value accepted is 20 (if
         you provide a value less than 20, it is reset to 0 and a warning is
         issued).  This limit is defined because otherwise you'll spend more
         time re-flushing a too small cache than working
         """
     )
     color_info = CBool(True, config=True, help=
         """
         Use colors for displaying information about objects. Because this
         information is passed through a pager (like 'less'), and some pagers
         get confused with color codes, this capability can be turned off.
         """
     )
     colors = CaselessStrEnum(('NoColor','LightBG','Linux'),
                              default_value=get_default_colors(), config=True,
         help="Set the color scheme (NoColor, Linux, or LightBG)."
     )
     colors_force = CBool(False, help=
         """
         Force use of ANSI color codes, regardless of OS and readline
         availability.
         """
         # FIXME: This is essentially a hack to allow ZMQShell to show colors
         # without readline on Win32. When the ZMQ formatting system is
         # refactored, this should be removed.
     )
     debug = CBool(False, config=True)
     deep_reload = CBool(False, config=True, help=
         """
         Enable deep (recursive) reloading by default. IPython can use the
         deep_reload module which reloads changes in modules recursively (it
         replaces the reload() function, so you don't need to change anything to
         use it). deep_reload() forces a full reload of modules whose code may
         have changed, which the default reload() function does not.  When
         deep_reload is off, IPython will use the normal reload(), but
         deep_reload will still be available as dreload().
         """
     )
     disable_failing_post_execute = CBool(False, config=True,
         help="Don't call post-execute functions that have failed in the past."
     )
     display_formatter = Instance(DisplayFormatter)
     displayhook_class = Type(DisplayHook)
     display_pub_class = Type(DisplayPublisher)
     data_pub_class = None
 
     exit_now = CBool(False)
     exiter = Instance(ExitAutocall)
     def _exiter_default(self):
         return ExitAutocall(self)
     # Monotonically increasing execution counter
     execution_count = Integer(1)
     filename = Unicode("<ipython console>")
     ipython_dir= Unicode('', config=True) # Set to get_ipython_dir() in __init__
 
     # Input splitter, to transform input line by line and detect when a block
     # is ready to be executed.
     input_splitter = Instance('IPython.core.inputsplitter.IPythonInputSplitter',
                               (), {'line_input_checker': True})
     
     # This InputSplitter instance is used to transform completed cells before
     # running them. It allows cell magics to contain blank lines.
     input_transformer_manager = Instance('IPython.core.inputsplitter.IPythonInputSplitter',
                                          (), {'line_input_checker': False})
     
     logstart = CBool(False, config=True, help=
         """
         Start logging to the default log file.
         """
     )
     logfile = Unicode('', config=True, help=
         """
         The name of the logfile to use.
         """
     )
     logappend = Unicode('', config=True, help=
         """
         Start logging to the given file in append mode.
         """
     )
     object_info_string_level = Enum((0,1,2), default_value=0,
                                     config=True)
     pdb = CBool(False, config=True, help=
         """
         Automatically call the pdb debugger after every exception.
         """
     )
     multiline_history = CBool(sys.platform != 'win32', config=True,
         help="Save multi-line entries as one entry in readline history"
     )
 
     # deprecated prompt traits:
     
     prompt_in1 = Unicode('In [\\#]: ', config=True,
         help="Deprecated, use PromptManager.in_template")
     prompt_in2 = Unicode('   .\\D.: ', config=True,
         help="Deprecated, use PromptManager.in2_template")
     prompt_out = Unicode('Out[\\#]: ', config=True,
         help="Deprecated, use PromptManager.out_template")
     prompts_pad_left = CBool(True, config=True,
         help="Deprecated, use PromptManager.justify")
     
     def _prompt_trait_changed(self, name, old, new):
         table = {
             'prompt_in1' : 'in_template',
             'prompt_in2' : 'in2_template',
             'prompt_out' : 'out_template',
             'prompts_pad_left' : 'justify',
         }
         warn("InteractiveShell.{name} is deprecated, use PromptManager.{newname}".format(
                 name=name, newname=table[name])
         )
         # protect against weird cases where self.config may not exist:
         if self.config is not None:
             # propagate to corresponding PromptManager trait
             setattr(self.config.PromptManager, table[name], new)
     
     _prompt_in1_changed = _prompt_trait_changed
     _prompt_in2_changed = _prompt_trait_changed
     _prompt_out_changed = _prompt_trait_changed
     _prompt_pad_left_changed = _prompt_trait_changed
     
     show_rewritten_input = CBool(True, config=True,
         help="Show rewritten input, e.g. for autocall."
     )
     
     quiet = CBool(False, config=True)
 
     history_length = Integer(10000, config=True)
 
     # The readline stuff will eventually be moved to the terminal subclass
     # but for now, we can't do that as readline is welded in everywhere.
     readline_use = CBool(True, config=True)
     readline_remove_delims = Unicode('-/~', config=True)
     readline_delims = Unicode() # set by init_readline()
     # don't use \M- bindings by default, because they
     # conflict with 8-bit encodings. See gh-58,gh-88
     readline_parse_and_bind = List([
             'tab: complete',
             '"\C-l": clear-screen',
             'set show-all-if-ambiguous on',
             '"\C-o": tab-insert',
             '"\C-r": reverse-search-history',
             '"\C-s": forward-search-history',
             '"\C-p": history-search-backward',
             '"\C-n": history-search-forward',
             '"\e[A": history-search-backward',
             '"\e[B": history-search-forward',
             '"\C-k": kill-line',
             '"\C-u": unix-line-discard',
         ], allow_none=False, config=True)
 
     ast_node_interactivity = Enum(['all', 'last', 'last_expr', 'none'],
                                   default_value='last_expr', config=True, 
                                   help="""
         'all', 'last', 'last_expr' or 'none', specifying which nodes should be
         run interactively (displaying output from expressions).""")
 
     # TODO: this part of prompt management should be moved to the frontends.
     # Use custom TraitTypes that convert '0'->'' and '\\n'->'\n'
     separate_in = SeparateUnicode('\n', config=True)
     separate_out = SeparateUnicode('', config=True)
     separate_out2 = SeparateUnicode('', config=True)
     wildcards_case_sensitive = CBool(True, config=True)
     xmode = CaselessStrEnum(('Context','Plain', 'Verbose'),
                             default_value='Context', config=True)
 
     # Subcomponents of InteractiveShell
     alias_manager = Instance('IPython.core.alias.AliasManager')
     prefilter_manager = Instance('IPython.core.prefilter.PrefilterManager')
     builtin_trap = Instance('IPython.core.builtin_trap.BuiltinTrap')
     display_trap = Instance('IPython.core.display_trap.DisplayTrap')
     extension_manager = Instance('IPython.core.extensions.ExtensionManager')
     payload_manager = Instance('IPython.core.payload.PayloadManager')
     history_manager = Instance('IPython.core.history.HistoryManager')
     magics_manager = Instance('IPython.core.magic.MagicsManager')
 
     profile_dir = Instance('IPython.core.application.ProfileDir')
     @property
     def profile(self):
         if self.profile_dir is not None:
             name = os.path.basename(self.profile_dir.location)
             return name.replace('profile_','')
 
 
     # Private interface
     _post_execute = Instance(dict)
 
     # Tracks any GUI loop loaded for pylab
     pylab_gui_select = None
 
     def __init__(self, ipython_dir=None, profile_dir=None,
                  user_module=None, user_ns=None,
                  custom_exceptions=((), None), **kwargs):
 
         # This is where traits with a config_key argument are updated
         # from the values on config.
         super(InteractiveShell, self).__init__(**kwargs)
         self.configurables = [self]
 
         # These are relatively independent and stateless
         self.init_ipython_dir(ipython_dir)
         self.init_profile_dir(profile_dir)
         self.init_instance_attrs()
         self.init_environment()
         
         # Check if we're in a virtualenv, and set up sys.path.
         self.init_virtualenv()
 
         # Create namespaces (user_ns, user_global_ns, etc.)
         self.init_create_namespaces(user_module, user_ns)
         # This has to be done after init_create_namespaces because it uses
         # something in self.user_ns, but before init_sys_modules, which
         # is the first thing to modify sys.
         # TODO: When we override sys.stdout and sys.stderr before this class
         # is created, we are saving the overridden ones here. Not sure if this
         # is what we want to do.
         self.save_sys_module_state()
         self.init_sys_modules()
 
         # While we're trying to have each part of the code directly access what
         # it needs without keeping redundant references to objects, we have too
         # much legacy code that expects ip.db to exist.
         self.db = PickleShareDB(os.path.join(self.profile_dir.location, 'db'))
 
         self.init_history()
         self.init_encoding()
         self.init_prefilter()
 
         self.init_syntax_highlighting()
         self.init_hooks()
         self.init_pushd_popd_magic()
         # self.init_traceback_handlers use to be here, but we moved it below
         # because it and init_io have to come after init_readline.
         self.init_user_ns()
         self.init_logger()
         self.init_builtins()
 
         # The following was in post_config_initialization
         self.init_inspector()
         # init_readline() must come before init_io(), because init_io uses
         # readline related things.
         self.init_readline()
         # We save this here in case user code replaces raw_input, but it needs
         # to be after init_readline(), because PyPy's readline works by replacing
         # raw_input.
         if py3compat.PY3:
             self.raw_input_original = input
         else:
             self.raw_input_original = raw_input
         # init_completer must come after init_readline, because it needs to
         # know whether readline is present or not system-wide to configure the
         # completers, since the completion machinery can now operate
         # independently of readline (e.g. over the network)
         self.init_completer()
         # TODO: init_io() needs to happen before init_traceback handlers
         # because the traceback handlers hardcode the stdout/stderr streams.
         # This logic in in debugger.Pdb and should eventually be changed.
         self.init_io()
         self.init_traceback_handlers(custom_exceptions)
         self.init_prompts()
         self.init_display_formatter()
         self.init_display_pub()
         self.init_data_pub()
         self.init_displayhook()
         self.init_latextool()
         self.init_magics()
         self.init_alias()
         self.init_logstart()
         self.init_pdb()
         self.init_extension_manager()
         self.init_payload()
         self.init_comms()
         self.hooks.late_startup_hook()
         atexit.register(self.atexit_operations)
 
     def get_ipython(self):
         """Return the currently running IPython instance."""
         return self
 
     #-------------------------------------------------------------------------
     # Trait changed handlers
     #-------------------------------------------------------------------------
 
     def _ipython_dir_changed(self, name, new):
         if not os.path.isdir(new):
             os.makedirs(new, mode = 0o777)
 
     def set_autoindent(self,value=None):
         """Set the autoindent flag, checking for readline support.
 
         If called with no arguments, it acts as a toggle."""
 
         if value != 0 and not self.has_readline:
             if os.name == 'posix':
                 warn("The auto-indent feature requires the readline library")
             self.autoindent = 0
             return
         if value is None:
             self.autoindent = not self.autoindent
         else:
             self.autoindent = value
 
     #-------------------------------------------------------------------------
     # init_* methods called by __init__
     #-------------------------------------------------------------------------
 
     def init_ipython_dir(self, ipython_dir):
         if ipython_dir is not None:
             self.ipython_dir = ipython_dir
             return
 
         self.ipython_dir = get_ipython_dir()
 
     def init_profile_dir(self, profile_dir):
         if profile_dir is not None:
             self.profile_dir = profile_dir
             return
         self.profile_dir =\
             ProfileDir.create_profile_dir_by_name(self.ipython_dir, 'default')
 
     def init_instance_attrs(self):
         self.more = False
 
         # command compiler
         self.compile = CachingCompiler()
 
         # Make an empty namespace, which extension writers can rely on both
         # existing and NEVER being used by ipython itself.  This gives them a
         # convenient location for storing additional information and state
         # their extensions may require, without fear of collisions with other
         # ipython names that may develop later.
         self.meta = Struct()
 
         # Temporary files used for various purposes.  Deleted at exit.
         self.tempfiles = []
 
         # Keep track of readline usage (later set by init_readline)
         self.has_readline = False
 
         # keep track of where we started running (mainly for crash post-mortem)
         # This is not being used anywhere currently.
         self.starting_dir = os.getcwdu()
 
         # Indentation management
         self.indent_current_nsp = 0
 
         # Dict to track post-execution functions that have been registered
         self._post_execute = {}
 
     def init_environment(self):
         """Any changes we need to make to the user's environment."""
         pass
 
     def init_encoding(self):
         # Get system encoding at startup time.  Certain terminals (like Emacs
         # under Win32 have it set to None, and we need to have a known valid
         # encoding to use in the raw_input() method
         try:
             self.stdin_encoding = sys.stdin.encoding or 'ascii'
         except AttributeError:
             self.stdin_encoding = 'ascii'
 
     def init_syntax_highlighting(self):
         # Python source parser/formatter for syntax highlighting
         pyformat = PyColorize.Parser().format
         self.pycolorize = lambda src: pyformat(src,'str',self.colors)
 
     def init_pushd_popd_magic(self):
         # for pushd/popd management
         self.home_dir = get_home_dir()
 
         self.dir_stack = []
 
     def init_logger(self):
         self.logger = Logger(self.home_dir, logfname='ipython_log.py',
                              logmode='rotate')
 
     def init_logstart(self):
         """Initialize logging in case it was requested at the command line.
         """
         if self.logappend:
             self.magic('logstart %s append' % self.logappend)
         elif self.logfile:
             self.magic('logstart %s' % self.logfile)
         elif self.logstart:
             self.magic('logstart')
 
     def init_builtins(self):
         # A single, static flag that we set to True.  Its presence indicates
         # that an IPython shell has been created, and we make no attempts at
         # removing on exit or representing the existence of more than one
         # IPython at a time.
         builtin_mod.__dict__['__IPYTHON__'] = True
 
         # In 0.11 we introduced '__IPYTHON__active' as an integer we'd try to
         # manage on enter/exit, but with all our shells it's virtually
         # impossible to get all the cases right.  We're leaving the name in for
         # those who adapted their codes to check for this flag, but will
         # eventually remove it after a few more releases.
         builtin_mod.__dict__['__IPYTHON__active'] = \
                                           'Deprecated, check for __IPYTHON__'
 
         self.builtin_trap = BuiltinTrap(shell=self)
 
     def init_inspector(self):
         # Object inspector
         self.inspector = oinspect.Inspector(oinspect.InspectColors,
                                             PyColorize.ANSICodeColors,
                                             'NoColor',
                                             self.object_info_string_level)
 
     def init_io(self):
         # This will just use sys.stdout and sys.stderr. If you want to
         # override sys.stdout and sys.stderr themselves, you need to do that
         # *before* instantiating this class, because io holds onto
         # references to the underlying streams.
         if (sys.platform == 'win32' or sys.platform == 'cli') and self.has_readline:
             io.stdout = io.stderr = io.IOStream(self.readline._outputfile)
         else:
             io.stdout = io.IOStream(sys.stdout)
             io.stderr = io.IOStream(sys.stderr)
 
     def init_prompts(self):
         self.prompt_manager = PromptManager(shell=self, parent=self)
         self.configurables.append(self.prompt_manager)
         # Set system prompts, so that scripts can decide if they are running
         # interactively.
         sys.ps1 = 'In : '
         sys.ps2 = '...: '
         sys.ps3 = 'Out: '
 
     def init_display_formatter(self):
         self.display_formatter = DisplayFormatter(parent=self)
         self.configurables.append(self.display_formatter)
 
     def init_display_pub(self):
         self.display_pub = self.display_pub_class(parent=self)
         self.configurables.append(self.display_pub)
 
     def init_data_pub(self):
         if not self.data_pub_class:
             self.data_pub = None
             return
         self.data_pub = self.data_pub_class(parent=self)
         self.configurables.append(self.data_pub)
 
     def init_displayhook(self):
         # Initialize displayhook, set in/out prompts and printing system
         self.displayhook = self.displayhook_class(
             parent=self,
             shell=self,
             cache_size=self.cache_size,
         )
         self.configurables.append(self.displayhook)
         # This is a context manager that installs/revmoes the displayhook at
         # the appropriate time.
         self.display_trap = DisplayTrap(hook=self.displayhook)
 
     def init_latextool(self):
         """Configure LaTeXTool."""
         cfg = LaTeXTool.instance(parent=self)
         if cfg not in self.configurables:
             self.configurables.append(cfg)
 
     def init_virtualenv(self):
         """Add a virtualenv to sys.path so the user can import modules from it.
         This isn't perfect: it doesn't use the Python interpreter with which the
         virtualenv was built, and it ignores the --no-site-packages option. A
         warning will appear suggesting the user installs IPython in the
         virtualenv, but for many cases, it probably works well enough.
         
         Adapted from code snippets online.
         
         http://blog.ufsoft.org/2009/1/29/ipython-and-virtualenv
         """
         if 'VIRTUAL_ENV' not in os.environ:
             # Not in a virtualenv
             return
         
         if sys.executable.startswith(os.environ['VIRTUAL_ENV']):
             # Running properly in the virtualenv, don't need to do anything
             return
         
         warn("Attempting to work in a virtualenv. If you encounter problems, please "
              "install IPython inside the virtualenv.")
         if sys.platform == "win32":
             virtual_env = os.path.join(os.environ['VIRTUAL_ENV'], 'Lib', 'site-packages') 
         else:
             virtual_env = os.path.join(os.environ['VIRTUAL_ENV'], 'lib',
                        'python%d.%d' % sys.version_info[:2], 'site-packages')
         
         import site
         sys.path.insert(0, virtual_env)
         site.addsitedir(virtual_env)
 
     #-------------------------------------------------------------------------
     # Things related to injections into the sys module
     #-------------------------------------------------------------------------
 
     def save_sys_module_state(self):
         """Save the state of hooks in the sys module.
 
         This has to be called after self.user_module is created.
         """
         self._orig_sys_module_state = {}
         self._orig_sys_module_state['stdin'] = sys.stdin
         self._orig_sys_module_state['stdout'] = sys.stdout
         self._orig_sys_module_state['stderr'] = sys.stderr
         self._orig_sys_module_state['excepthook'] = sys.excepthook
         self._orig_sys_modules_main_name = self.user_module.__name__
         self._orig_sys_modules_main_mod = sys.modules.get(self.user_module.__name__)
 
     def restore_sys_module_state(self):
         """Restore the state of the sys module."""
         try:
             for k, v in self._orig_sys_module_state.iteritems():
                 setattr(sys, k, v)
         except AttributeError:
             pass
         # Reset what what done in self.init_sys_modules
         if self._orig_sys_modules_main_mod is not None:
             sys.modules[self._orig_sys_modules_main_name] = self._orig_sys_modules_main_mod
 
     #-------------------------------------------------------------------------
     # Things related to hooks
     #-------------------------------------------------------------------------
 
     def init_hooks(self):
         # hooks holds pointers used for user-side customizations
         self.hooks = Struct()
 
         self.strdispatchers = {}
 
         # Set all default hooks, defined in the IPython.hooks module.
         hooks = IPython.core.hooks
         for hook_name in hooks.__all__:
             # default hooks have priority 100, i.e. low; user hooks should have
             # 0-100 priority
             self.set_hook(hook_name,getattr(hooks,hook_name), 100)
 
     def set_hook(self,name,hook, priority = 50, str_key = None, re_key = None):
         """set_hook(name,hook) -> sets an internal IPython hook.
 
         IPython exposes some of its internal API as user-modifiable hooks.  By
         adding your function to one of these hooks, you can modify IPython's
         behavior to call at runtime your own routines."""
 
         # At some point in the future, this should validate the hook before it
         # accepts it.  Probably at least check that the hook takes the number
         # of args it's supposed to.
 
         f = types.MethodType(hook,self)
 
         # check if the hook is for strdispatcher first
         if str_key is not None:
             sdp = self.strdispatchers.get(name, StrDispatch())
             sdp.add_s(str_key, f, priority )
             self.strdispatchers[name] = sdp
             return
         if re_key is not None:
             sdp = self.strdispatchers.get(name, StrDispatch())
             sdp.add_re(re.compile(re_key), f, priority )
             self.strdispatchers[name] = sdp
             return
 
         dp = getattr(self.hooks, name, None)
         if name not in IPython.core.hooks.__all__:
             print("Warning! Hook '%s' is not one of %s" % \
                   (name, IPython.core.hooks.__all__ ))
         if not dp:
             dp = IPython.core.hooks.CommandChainDispatcher()
 
         try:
             dp.add(f,priority)
         except AttributeError:
             # it was not commandchain, plain old func - replace
             dp = f
 
         setattr(self.hooks,name, dp)
 
     def register_post_execute(self, func):
         """Register a function for calling after code execution.
         """
         if not callable(func):
             raise ValueError('argument %s must be callable' % func)
         self._post_execute[func] = True
     
     #-------------------------------------------------------------------------
     # Things related to the "main" module
     #-------------------------------------------------------------------------
 
     def new_main_mod(self, filename, modname):
         """Return a new 'main' module object for user code execution.
         
         ``filename`` should be the path of the script which will be run in the
         module. Requests with the same filename will get the same module, with
         its namespace cleared.
         
         ``modname`` should be the module name - normally either '__main__' or
         the basename of the file without the extension.
         
         When scripts are executed via %run, we must keep a reference to their
         __main__ module around so that Python doesn't
         clear it, rendering references to module globals useless.
 
         This method keeps said reference in a private dict, keyed by the
         absolute path of the script. This way, for multiple executions of the
         same script we only keep one copy of the namespace (the last one),
         thus preventing memory leaks from old references while allowing the
         objects from the last execution to be accessible.
         """
         filename = os.path.abspath(filename)
         try:
             main_mod = self._main_mod_cache[filename]
         except KeyError:
             main_mod = self._main_mod_cache[filename] = types.ModuleType(modname,
                         doc="Module created for script run in IPython")
         else:
             main_mod.__dict__.clear()
             main_mod.__name__ = modname
         
         main_mod.__file__ = filename
         # It seems pydoc (and perhaps others) needs any module instance to
         # implement a __nonzero__ method
         main_mod.__nonzero__ = lambda : True
         
         return main_mod
 
     def clear_main_mod_cache(self):
         """Clear the cache of main modules.
 
         Mainly for use by utilities like %reset.
 
         Examples
         --------
 
         In [15]: import IPython
 
         In [16]: m = _ip.new_main_mod(IPython.__file__, 'IPython')
 
         In [17]: len(_ip._main_mod_cache) > 0
         Out[17]: True
 
         In [18]: _ip.clear_main_mod_cache()
 
         In [19]: len(_ip._main_mod_cache) == 0
         Out[19]: True
         """
         self._main_mod_cache.clear()
 
     #-------------------------------------------------------------------------
     # Things related to debugging
     #-------------------------------------------------------------------------
 
     def init_pdb(self):
         # Set calling of pdb on exceptions
         # self.call_pdb is a property
         self.call_pdb = self.pdb
 
     def _get_call_pdb(self):
         return self._call_pdb
 
     def _set_call_pdb(self,val):
 
         if val not in (0,1,False,True):
             raise ValueError('new call_pdb value must be boolean')
 
         # store value in instance
         self._call_pdb = val
 
         # notify the actual exception handlers
         self.InteractiveTB.call_pdb = val
 
     call_pdb = property(_get_call_pdb,_set_call_pdb,None,
                         'Control auto-activation of pdb at exceptions')
 
     def debugger(self,force=False):
         """Call the pydb/pdb debugger.
 
         Keywords:
 
           - force(False): by default, this routine checks the instance call_pdb
             flag and does not actually invoke the debugger if the flag is false.
             The 'force' option forces the debugger to activate even if the flag
             is false.
         """
 
         if not (force or self.call_pdb):
             return
 
         if not hasattr(sys,'last_traceback'):
             error('No traceback has been produced, nothing to debug.')
             return
 
         # use pydb if available
         if debugger.has_pydb:
             from pydb import pm
         else:
             # fallback to our internal debugger
             pm = lambda : self.InteractiveTB.debugger(force=True)
 
         with self.readline_no_record:
             pm()
 
     #-------------------------------------------------------------------------
     # Things related to IPython's various namespaces
     #-------------------------------------------------------------------------
     default_user_namespaces = True
 
     def init_create_namespaces(self, user_module=None, user_ns=None):
         # Create the namespace where the user will operate.  user_ns is
         # normally the only one used, and it is passed to the exec calls as
         # the locals argument.  But we do carry a user_global_ns namespace
         # given as the exec 'globals' argument,  This is useful in embedding
         # situations where the ipython shell opens in a context where the
         # distinction between locals and globals is meaningful.  For
         # non-embedded contexts, it is just the same object as the user_ns dict.
 
         # FIXME. For some strange reason, __builtins__ is showing up at user
         # level as a dict instead of a module. This is a manual fix, but I
         # should really track down where the problem is coming from. Alex
         # Schmolck reported this problem first.
 
         # A useful post by Alex Martelli on this topic:
         # Re: inconsistent value from __builtins__
         # Von: Alex Martelli <[e-mail]>
         # Datum: Freitag 01 Oktober 2004 04:45:34 nachmittags/abends
         # Gruppen: comp.lang.python
 
         # Michael Hohn <[e-mail]> wrote:
         # > >>> print type(builtin_check.get_global_binding('__builtins__'))
         # > <type 'dict'>
         # > >>> print type(__builtins__)
         # > <type 'module'>
         # > Is this difference in return value intentional?
 
         # Well, it's documented that '__builtins__' can be either a dictionary
         # or a module, and it's been that way for a long time. Whether it's
         # intentional (or sensible), I don't know. In any case, the idea is
         # that if you need to access the built-in namespace directly, you
         # should start with "import __builtin__" (note, no 's') which will
         # definitely give you a module. Yeah, it's somewhat confusing:-(.
 
         # These routines return a properly built module and dict as needed by
         # the rest of the code, and can also be used by extension writers to
         # generate properly initialized namespaces.
         if (user_ns is not None) or (user_module is not None):
             self.default_user_namespaces = False
         self.user_module, self.user_ns = self.prepare_user_module(user_module, user_ns)
 
         # A record of hidden variables we have added to the user namespace, so
         # we can list later only variables defined in actual interactive use.
         self.user_ns_hidden = {}
 
         # Now that FakeModule produces a real module, we've run into a nasty
         # problem: after script execution (via %run), the module where the user
         # code ran is deleted.  Now that this object is a true module (needed
         # so docetst and other tools work correctly), the Python module
         # teardown mechanism runs over it, and sets to None every variable
         # present in that module.  Top-level references to objects from the
         # script survive, because the user_ns is updated with them.  However,
         # calling functions defined in the script that use other things from
         # the script will fail, because the function's closure had references
         # to the original objects, which are now all None.  So we must protect
         # these modules from deletion by keeping a cache.
         #
         # To avoid keeping stale modules around (we only need the one from the
         # last run), we use a dict keyed with the full path to the script, so
         # only the last version of the module is held in the cache.  Note,
         # however, that we must cache the module *namespace contents* (their
         # __dict__).  Because if we try to cache the actual modules, old ones
         # (uncached) could be destroyed while still holding references (such as
         # those held by GUI objects that tend to be long-lived)>
         #
         # The %reset command will flush this cache.  See the cache_main_mod()
         # and clear_main_mod_cache() methods for details on use.
 
         # This is the cache used for 'main' namespaces
         self._main_mod_cache = {}
 
         # A table holding all the namespaces IPython deals with, so that
         # introspection facilities can search easily.
         self.ns_table = {'user_global':self.user_module.__dict__,
                          'user_local':self.user_ns,
                          'builtin':builtin_mod.__dict__
                          }
     
     @property
     def user_global_ns(self):
         return self.user_module.__dict__
 
     def prepare_user_module(self, user_module=None, user_ns=None):
         """Prepare the module and namespace in which user code will be run.
         
         When IPython is started normally, both parameters are None: a new module
         is created automatically, and its __dict__ used as the namespace.
         
         If only user_module is provided, its __dict__ is used as the namespace.
         If only user_ns is provided, a dummy module is created, and user_ns
         becomes the global namespace. If both are provided (as they may be
         when embedding), user_ns is the local namespace, and user_module
         provides the global namespace.
 
         Parameters
         ----------
         user_module : module, optional
             The current user module in which IPython is being run. If None,
             a clean module will be created.
         user_ns : dict, optional
             A namespace in which to run interactive commands.
 
         Returns
         -------
         A tuple of user_module and user_ns, each properly initialised.
         """
         if user_module is None and user_ns is not None:
             user_ns.setdefault("__name__", "__main__")
             user_module = DummyMod()
             user_module.__dict__ = user_ns
             
         if user_module is None:
             user_module = types.ModuleType("__main__",
                 doc="Automatically created module for IPython interactive environment")
         
         # We must ensure that __builtin__ (without the final 's') is always
         # available and pointing to the __builtin__ *module*.  For more details:
         # http://mail.python.org/pipermail/python-dev/2001-April/014068.html
         user_module.__dict__.setdefault('__builtin__', builtin_mod)
         user_module.__dict__.setdefault('__builtins__', builtin_mod)
         
         if user_ns is None:
             user_ns = user_module.__dict__
 
         return user_module, user_ns
 
     def init_sys_modules(self):
         # We need to insert into sys.modules something that looks like a
         # module but which accesses the IPython namespace, for shelve and
         # pickle to work interactively. Normally they rely on getting
         # everything out of __main__, but for embedding purposes each IPython
         # instance has its own private namespace, so we can't go shoving
         # everything into __main__.
 
         # note, however, that we should only do this for non-embedded
         # ipythons, which really mimic the __main__.__dict__ with their own
         # namespace.  Embedded instances, on the other hand, should not do
         # this because they need to manage the user local/global namespaces
         # only, but they live within a 'normal' __main__ (meaning, they
         # shouldn't overtake the execution environment of the script they're
         # embedded in).
 
         # This is overridden in the InteractiveShellEmbed subclass to a no-op.
         main_name = self.user_module.__name__
         sys.modules[main_name] = self.user_module
 
     def init_user_ns(self):
         """Initialize all user-visible namespaces to their minimum defaults.
 
         Certain history lists are also initialized here, as they effectively
         act as user namespaces.
 
         Notes
         -----
         All data structures here are only filled in, they are NOT reset by this
         method.  If they were not empty before, data will simply be added to
         therm.
         """
         # This function works in two parts: first we put a few things in
         # user_ns, and we sync that contents into user_ns_hidden so that these
         # initial variables aren't shown by %who.  After the sync, we add the
         # rest of what we *do* want the user to see with %who even on a new
         # session (probably nothing, so theye really only see their own stuff)
 
         # The user dict must *always* have a __builtin__ reference to the
         # Python standard __builtin__ namespace,  which must be imported.
         # This is so that certain operations in prompt evaluation can be
         # reliably executed with builtins.  Note that we can NOT use
         # __builtins__ (note the 's'),  because that can either be a dict or a
         # module, and can even mutate at runtime, depending on the context
         # (Python makes no guarantees on it).  In contrast, __builtin__ is
         # always a module object, though it must be explicitly imported.
 
         # For more details:
         # http://mail.python.org/pipermail/python-dev/2001-April/014068.html
         ns = dict()
         
         # Put 'help' in the user namespace
         try:
             from site import _Helper
             ns['help'] = _Helper()
         except ImportError:
             warn('help() not available - check site.py')
 
         # make global variables for user access to the histories
         ns['_ih'] = self.history_manager.input_hist_parsed
         ns['_oh'] = self.history_manager.output_hist
         ns['_dh'] = self.history_manager.dir_hist
 
         ns['_sh'] = shadowns
 
         # user aliases to input and output histories.  These shouldn't show up
         # in %who, as they can have very large reprs.
         ns['In']  = self.history_manager.input_hist_parsed
         ns['Out'] = self.history_manager.output_hist
 
         # Store myself as the public api!!!
         ns['get_ipython'] = self.get_ipython
         
         ns['exit'] = self.exiter
         ns['quit'] = self.exiter
 
         # Sync what we've added so far to user_ns_hidden so these aren't seen
         # by %who
         self.user_ns_hidden.update(ns)
 
         # Anything put into ns now would show up in %who.  Think twice before
         # putting anything here, as we really want %who to show the user their
         # stuff, not our variables.
 
         # Finally, update the real user's namespace
         self.user_ns.update(ns)
     
     @property
     def all_ns_refs(self):
         """Get a list of references to all the namespace dictionaries in which
         IPython might store a user-created object.
         
         Note that this does not include the displayhook, which also caches
         objects from the output."""
         return [self.user_ns, self.user_global_ns, self.user_ns_hidden] + \
                [m.__dict__ for m in self._main_mod_cache.values()]
 
     def reset(self, new_session=True):
         """Clear all internal namespaces, and attempt to release references to
         user objects.
 
         If new_session is True, a new history session will be opened.
         """
         # Clear histories
         self.history_manager.reset(new_session)
         # Reset counter used to index all histories
         if new_session:
             self.execution_count = 1
 
         # Flush cached output items
         if self.displayhook.do_full_cache:
             self.displayhook.flush()
 
         # The main execution namespaces must be cleared very carefully,
         # skipping the deletion of the builtin-related keys, because doing so
         # would cause errors in many object's __del__ methods.
         if self.user_ns is not self.user_global_ns:
             self.user_ns.clear()
         ns = self.user_global_ns
         drop_keys = set(ns.keys())
         drop_keys.discard('__builtin__')
         drop_keys.discard('__builtins__')
         drop_keys.discard('__name__')
         for k in drop_keys:
             del ns[k]
         
         self.user_ns_hidden.clear()
         
         # Restore the user namespaces to minimal usability
         self.init_user_ns()
 
         # Restore the default and user aliases
         self.alias_manager.clear_aliases()
         self.alias_manager.init_aliases()
 
         # Flush the private list of module references kept for script
         # execution protection
         self.clear_main_mod_cache()
 
     def del_var(self, varname, by_name=False):
         """Delete a variable from the various namespaces, so that, as
         far as possible, we're not keeping any hidden references to it.
 
         Parameters
         ----------
         varname : str
             The name of the variable to delete.
         by_name : bool
             If True, delete variables with the given name in each
             namespace. If False (default), find the variable in the user
             namespace, and delete references to it.
         """
         if varname in ('__builtin__', '__builtins__'):
             raise ValueError("Refusing to delete %s" % varname)
 
         ns_refs = self.all_ns_refs
         
         if by_name:                    # Delete by name
             for ns in ns_refs:
                 try:
                     del ns[varname]
                 except KeyError:
                     pass
         else:                         # Delete by object
             try:
                 obj = self.user_ns[varname]
             except KeyError:
                 raise NameError("name '%s' is not defined" % varname)
             # Also check in output history
             ns_refs.append(self.history_manager.output_hist)
             for ns in ns_refs:
                 to_delete = [n for n, o in ns.iteritems() if o is obj]
                 for name in to_delete:
                     del ns[name]
 
             # displayhook keeps extra references, but not in a dictionary
             for name in ('_', '__', '___'):
                 if getattr(self.displayhook, name) is obj:
                     setattr(self.displayhook, name, None)
 
     def reset_selective(self, regex=None):
         """Clear selective variables from internal namespaces based on a
         specified regular expression.
 
         Parameters
         ----------
         regex : string or compiled pattern, optional
             A regular expression pattern that will be used in searching
             variable names in the users namespaces.
         """
         if regex is not None:
             try:
                 m = re.compile(regex)
             except TypeError:
                 raise TypeError('regex must be a string or compiled pattern')
             # Search for keys in each namespace that match the given regex
             # If a match is found, delete the key/value pair.
             for ns in self.all_ns_refs:
                 for var in ns:
                     if m.search(var):
                         del ns[var]
 
     def push(self, variables, interactive=True):
         """Inject a group of variables into the IPython user namespace.
 
         Parameters
         ----------
         variables : dict, str or list/tuple of str
             The variables to inject into the user's namespace.  If a dict, a
             simple update is done.  If a str, the string is assumed to have
             variable names separated by spaces.  A list/tuple of str can also
             be used to give the variable names.  If just the variable names are
             give (list/tuple/str) then the variable values looked up in the
             callers frame.
         interactive : bool
             If True (default), the variables will be listed with the ``who``
             magic.
         """
         vdict = None
 
         # We need a dict of name/value pairs to do namespace updates.
         if isinstance(variables, dict):
             vdict = variables
         elif isinstance(variables, string_types+(list, tuple)):
             if isinstance(variables, string_types):
                 vlist = variables.split()
             else:
                 vlist = variables
             vdict = {}
             cf = sys._getframe(1)
             for name in vlist:
                 try:
                     vdict[name] = eval(name, cf.f_globals, cf.f_locals)
                 except:
                     print('Could not get variable %s from %s' %
                            (name,cf.f_code.co_name))
         else:
             raise ValueError('variables must be a dict/str/list/tuple')
 
         # Propagate variables to user namespace
         self.user_ns.update(vdict)
 
         # And configure interactive visibility
         user_ns_hidden = self.user_ns_hidden
         if interactive:
             for name in vdict:
                 user_ns_hidden.pop(name, None)
         else:
             user_ns_hidden.update(vdict)
     
     def drop_by_id(self, variables):
         """Remove a dict of variables from the user namespace, if they are the
         same as the values in the dictionary.
         
         This is intended for use by extensions: variables that they've added can
         be taken back out if they are unloaded, without removing any that the
         user has overwritten.
         
         Parameters
         ----------
         variables : dict
           A dictionary mapping object names (as strings) to the objects.
         """
         for name, obj in variables.iteritems():
             if name in self.user_ns and self.user_ns[name] is obj:
                 del self.user_ns[name]
                 self.user_ns_hidden.pop(name, None)
 
     #-------------------------------------------------------------------------
     # Things related to object introspection
     #-------------------------------------------------------------------------
 
     def _ofind(self, oname, namespaces=None):
         """Find an object in the available namespaces.
 
         self._ofind(oname) -> dict with keys: found,obj,ospace,ismagic
 
         Has special code to detect magic functions.
         """
         oname = oname.strip()
         #print '1- oname: <%r>' % oname  # dbg
         if not oname.startswith(ESC_MAGIC) and \
             not oname.startswith(ESC_MAGIC2) and \
             not py3compat.isidentifier(oname, dotted=True):
             return dict(found=False)
 
         alias_ns = None
         if namespaces is None:
             # Namespaces to search in:
             # Put them in a list. The order is important so that we
             # find things in the same order that Python finds them.
             namespaces = [ ('Interactive', self.user_ns),
                            ('Interactive (global)', self.user_global_ns),
                            ('Python builtin', builtin_mod.__dict__),
                            ]
 
         # initialize results to 'null'
         found = False; obj = None;  ospace = None;  ds = None;
         ismagic = False; isalias = False; parent = None
 
         # We need to special-case 'print', which as of python2.6 registers as a
         # function but should only be treated as one if print_function was
         # loaded with a future import.  In this case, just bail.
         if (oname == 'print' and not py3compat.PY3 and not \
             (self.compile.compiler_flags & __future__.CO_FUTURE_PRINT_FUNCTION)):
             return {'found':found, 'obj':obj, 'namespace':ospace,
                     'ismagic':ismagic, 'isalias':isalias, 'parent':parent}
 
         # Look for the given name by splitting it in parts.  If the head is
         # found, then we look for all the remaining parts as members, and only
         # declare success if we can find them all.
         oname_parts = oname.split('.')
         oname_head, oname_rest = oname_parts[0],oname_parts[1:]
         for nsname,ns in namespaces:
             try:
                 obj = ns[oname_head]
             except KeyError:
                 continue
             else:
                 #print 'oname_rest:', oname_rest  # dbg
                 for part in oname_rest:
                     try:
                         parent = obj
                         obj = getattr(obj,part)
                     except:
                         # Blanket except b/c some badly implemented objects
                         # allow __getattr__ to raise exceptions other than
                         # AttributeError, which then crashes IPython.
                         break
                 else:
                     # If we finish the for loop (no break), we got all members
                     found = True
                     ospace = nsname
                     break  # namespace loop
 
         # Try to see if it's magic
         if not found:
             obj = None
             if oname.startswith(ESC_MAGIC2):
                 oname = oname.lstrip(ESC_MAGIC2)
                 obj = self.find_cell_magic(oname)
             elif oname.startswith(ESC_MAGIC):
                 oname = oname.lstrip(ESC_MAGIC)
                 obj = self.find_line_magic(oname)
             else:
                 # search without prefix, so run? will find %run?
                 obj = self.find_line_magic(oname)
                 if obj is None:
                     obj = self.find_cell_magic(oname)
             if obj is not None:
                 found = True
                 ospace = 'IPython internal'
                 ismagic = True
 
         # Last try: special-case some literals like '', [], {}, etc:
         if not found and oname_head in ["''",'""','[]','{}','()']:
             obj = eval(oname_head)
             found = True
             ospace = 'Interactive'
 
         return {'found':found, 'obj':obj, 'namespace':ospace,
                 'ismagic':ismagic, 'isalias':isalias, 'parent':parent}
 
     def _ofind_property(self, oname, info):
         """Second part of object finding, to look for property details."""
         if info.found:
             # Get the docstring of the class property if it exists.
             path = oname.split('.')
             root = '.'.join(path[:-1])
             if info.parent is not None:
                 try:
                     target = getattr(info.parent, '__class__')
                     # The object belongs to a class instance.
                     try:
                         target = getattr(target, path[-1])
                         # The class defines the object.
                         if isinstance(target, property):
                             oname = root + '.__class__.' + path[-1]
                             info = Struct(self._ofind(oname))
                     except AttributeError: pass
                 except AttributeError: pass
 
         # We return either the new info or the unmodified input if the object
         # hadn't been found
         return info
 
     def _object_find(self, oname, namespaces=None):
         """Find an object and return a struct with info about it."""
         inf = Struct(self._ofind(oname, namespaces))
         return Struct(self._ofind_property(oname, inf))
 
     def _inspect(self, meth, oname, namespaces=None, **kw):
         """Generic interface to the inspector system.
 
         This function is meant to be called by pdef, pdoc & friends."""
         info = self._object_find(oname, namespaces)
         if info.found:
             pmethod = getattr(self.inspector, meth)
             formatter = format_screen if info.ismagic else None
             if meth == 'pdoc':
                 pmethod(info.obj, oname, formatter)
             elif meth == 'pinfo':
                 pmethod(info.obj, oname, formatter, info, **kw)
             else:
                 pmethod(info.obj, oname)
         else:
             print('Object `%s` not found.' % oname)
             return 'not found'  # so callers can take other action
 
     def object_inspect(self, oname, detail_level=0):
         with self.builtin_trap:
             info = self._object_find(oname)
             if info.found:
                 return self.inspector.info(info.obj, oname, info=info,
                             detail_level=detail_level
                 )
             else:
                 return oinspect.object_info(name=oname, found=False)
 
     #-------------------------------------------------------------------------
     # Things related to history management
     #-------------------------------------------------------------------------
 
     def init_history(self):
         """Sets up the command history, and starts regular autosaves."""
         self.history_manager = HistoryManager(shell=self, parent=self)
         self.configurables.append(self.history_manager)
 
     #-------------------------------------------------------------------------
     # Things related to exception handling and tracebacks (not debugging)
     #-------------------------------------------------------------------------
 
     def init_traceback_handlers(self, custom_exceptions):
         # Syntax error handler.
         self.SyntaxTB = ultratb.SyntaxTB(color_scheme='NoColor')
 
         # The interactive one is initialized with an offset, meaning we always
         # want to remove the topmost item in the traceback, which is our own
         # internal code. Valid modes: ['Plain','Context','Verbose']
         self.InteractiveTB = ultratb.AutoFormattedTB(mode = 'Plain',
                                                      color_scheme='NoColor',
                                                      tb_offset = 1,
                                    check_cache=check_linecache_ipython)
 
         # The instance will store a pointer to the system-wide exception hook,
         # so that runtime code (such as magics) can access it.  This is because
         # during the read-eval loop, it may get temporarily overwritten.
         self.sys_excepthook = sys.excepthook
 
         # and add any custom exception handlers the user may have specified
         self.set_custom_exc(*custom_exceptions)
 
         # Set the exception mode
         self.InteractiveTB.set_mode(mode=self.xmode)
 
     def set_custom_exc(self, exc_tuple, handler):
         """set_custom_exc(exc_tuple,handler)
 
         Set a custom exception handler, which will be called if any of the
         exceptions in exc_tuple occur in the mainloop (specifically, in the
         run_code() method).
 
         Parameters
         ----------
 
         exc_tuple : tuple of exception classes
             A *tuple* of exception classes, for which to call the defined
             handler.  It is very important that you use a tuple, and NOT A
             LIST here, because of the way Python's except statement works.  If
             you only want to trap a single exception, use a singleton tuple::
 
                 exc_tuple == (MyCustomException,)
 
         handler : callable
             handler must have the following signature::
 
                 def my_handler(self, etype, value, tb, tb_offset=None):
                     ...
                     return structured_traceback
 
             Your handler must return a structured traceback (a list of strings),
             or None.
 
             This will be made into an instance method (via types.MethodType)
             of IPython itself, and it will be called if any of the exceptions
             listed in the exc_tuple are caught. If the handler is None, an
             internal basic one is used, which just prints basic info.
 
             To protect IPython from crashes, if your handler ever raises an
             exception or returns an invalid result, it will be immediately
             disabled.
 
         WARNING: by putting in your own exception handler into IPython's main
         execution loop, you run a very good chance of nasty crashes.  This
         facility should only be used if you really know what you are doing."""
 
         assert type(exc_tuple)==type(()) , \
                "The custom exceptions must be given AS A TUPLE."
 
         def dummy_handler(self,etype,value,tb,tb_offset=None):
             print('*** Simple custom exception handler ***')
             print('Exception type :',etype)
             print('Exception value:',value)
             print('Traceback      :',tb)
             #print 'Source code    :','\n'.join(self.buffer)
         
         def validate_stb(stb):
             """validate structured traceback return type
             
             return type of CustomTB *should* be a list of strings, but allow
             single strings or None, which are harmless.
             
             This function will *always* return a list of strings,
             and will raise a TypeError if stb is inappropriate.
             """
             msg = "CustomTB must return list of strings, not %r" % stb
             if stb is None:
                 return []
             elif isinstance(stb, string_types):
                 return [stb]
             elif not isinstance(stb, list):
                 raise TypeError(msg)
             # it's a list
             for line in stb:
                 # check every element
                 if not isinstance(line, string_types):
                     raise TypeError(msg)
             return stb
 
         if handler is None:
             wrapped = dummy_handler
         else:
             def wrapped(self,etype,value,tb,tb_offset=None):
                 """wrap CustomTB handler, to protect IPython from user code
                 
                 This makes it harder (but not impossible) for custom exception
                 handlers to crash IPython.
                 """
                 try:
                     stb = handler(self,etype,value,tb,tb_offset=tb_offset)
                     return validate_stb(stb)
                 except:
                     # clear custom handler immediately
                     self.set_custom_exc((), None)
                     print("Custom TB Handler failed, unregistering", file=io.stderr)
                     # show the exception in handler first
                     stb = self.InteractiveTB.structured_traceback(*sys.exc_info())
                     print(self.InteractiveTB.stb2text(stb), file=io.stdout)
                     print("The original exception:", file=io.stdout)
                     stb = self.InteractiveTB.structured_traceback(
                                             (etype,value,tb), tb_offset=tb_offset
                     )
                 return stb
 
         self.CustomTB = types.MethodType(wrapped,self)
         self.custom_exceptions = exc_tuple
 
     def excepthook(self, etype, value, tb):
       """One more defense for GUI apps that call sys.excepthook.
 
       GUI frameworks like wxPython trap exceptions and call
       sys.excepthook themselves.  I guess this is a feature that
       enables them to keep running after exceptions that would
       otherwise kill their mainloop. This is a bother for IPython
       which excepts to catch all of the program exceptions with a try:
       except: statement.
 
       Normally, IPython sets sys.excepthook to a CrashHandler instance, so if
       any app directly invokes sys.excepthook, it will look to the user like
       IPython crashed.  In order to work around this, we can disable the
       CrashHandler and replace it with this excepthook instead, which prints a
       regular traceback using our InteractiveTB.  In this fashion, apps which
       call sys.excepthook will generate a regular-looking exception from
       IPython, and the CrashHandler will only be triggered by real IPython
       crashes.
 
       This hook should be used sparingly, only in places which are not likely
       to be true IPython errors.
       """
       self.showtraceback((etype,value,tb),tb_offset=0)
 
     def _get_exc_info(self, exc_tuple=None):
         """get exc_info from a given tuple, sys.exc_info() or sys.last_type etc.
         
         Ensures sys.last_type,value,traceback hold the exc_info we found,
         from whichever source.
         
         raises ValueError if none of these contain any information
         """
         if exc_tuple is None:
             etype, value, tb = sys.exc_info()
         else:
             etype, value, tb = exc_tuple
 
         if etype is None:
             if hasattr(sys, 'last_type'):
                 etype, value, tb = sys.last_type, sys.last_value, \
                                    sys.last_traceback
         
         if etype is None:
             raise ValueError("No exception to find")
         
         # Now store the exception info in sys.last_type etc.
         # WARNING: these variables are somewhat deprecated and not
         # necessarily safe to use in a threaded environment, but tools
         # like pdb depend on their existence, so let's set them.  If we
         # find problems in the field, we'll need to revisit their use.
         sys.last_type = etype
         sys.last_value = value
         sys.last_traceback = tb
         
         return etype, value, tb
     
     def show_usage_error(self, exc):
         """Show a short message for UsageErrors
         
         These are special exceptions that shouldn't show a traceback.
         """
         self.write_err("UsageError: %s" % exc)
     
     def showtraceback(self,exc_tuple = None,filename=None,tb_offset=None,
                       exception_only=False):
         """Display the exception that just occurred.
 
         If nothing is known about the exception, this is the method which
         should be used throughout the code for presenting user tracebacks,
         rather than directly invoking the InteractiveTB object.
 
         A specific showsyntaxerror() also exists, but this method can take
         care of calling it if needed, so unless you are explicitly catching a
         SyntaxError exception, don't try to analyze the stack manually and
         simply call this method."""
 
         try:
             try:
                 etype, value, tb = self._get_exc_info(exc_tuple)
             except ValueError:
                 self.write_err('No traceback available to show.\n')
                 return
             
             if issubclass(etype, SyntaxError):
                 # Though this won't be called by syntax errors in the input
                 # line, there may be SyntaxError cases with imported code.
                 self.showsyntaxerror(filename)
             elif etype is UsageError:
                 self.show_usage_error(value)
             else:
                 if exception_only:
                     stb = ['An exception has occurred, use %tb to see '
                            'the full traceback.\n']
                     stb.extend(self.InteractiveTB.get_exception_only(etype,
                                                                      value))
                 else:
                     try:
                         # Exception classes can customise their traceback - we
                         # use this in IPython.parallel for exceptions occurring
                         # in the engines. This should return a list of strings.
                         stb = value._render_traceback_()
                     except Exception:
                         stb = self.InteractiveTB.structured_traceback(etype,
                                             value, tb, tb_offset=tb_offset)
 
                     self._showtraceback(etype, value, stb)
                     if self.call_pdb:
                         # drop into debugger
                         self.debugger(force=True)
                     return
 
                 # Actually show the traceback
                 self._showtraceback(etype, value, stb)
 
         except KeyboardInterrupt:
             self.write_err("\nKeyboardInterrupt\n")
 
     def _showtraceback(self, etype, evalue, stb):
         """Actually show a traceback.
 
         Subclasses may override this method to put the traceback on a different
         place, like a side channel.
         """
         print(self.InteractiveTB.stb2text(stb), file=io.stdout)
 
     def showsyntaxerror(self, filename=None):
         """Display the syntax error that just occurred.
 
         This doesn't display a stack trace because there isn't one.
 
         If a filename is given, it is stuffed in the exception instead
         of what was there before (because Python's parser always uses
         "<string>" when reading from a string).
         """
         etype, value, last_traceback = self._get_exc_info()
 
         if filename and issubclass(etype, SyntaxError):
             try:
                 value.filename = filename
             except:
                 # Not the format we expect; leave it alone
                 pass
         
         stb = self.SyntaxTB.structured_traceback(etype, value, [])
         self._showtraceback(etype, value, stb)
 
     # This is overridden in TerminalInteractiveShell to show a message about
     # the %paste magic.
     def showindentationerror(self):
         """Called by run_cell when there's an IndentationError in code entered
         at the prompt.
 
         This is overridden in TerminalInteractiveShell to show a message about
         the %paste magic."""
         self.showsyntaxerror()
 
     #-------------------------------------------------------------------------
     # Things related to readline
     #-------------------------------------------------------------------------
 
     def init_readline(self):
         """Command history completion/saving/reloading."""
 
         if self.readline_use:
             import IPython.utils.rlineimpl as readline
 
         self.rl_next_input = None
         self.rl_do_indent = False
 
         if not self.readline_use or not readline.have_readline:
             self.has_readline = False
             self.readline = None
             # Set a number of methods that depend on readline to be no-op
             self.readline_no_record = no_op_context
             self.set_readline_completer = no_op
             self.set_custom_completer = no_op
             if self.readline_use:
                 warn('Readline services not available or not loaded.')
         else:
             self.has_readline = True
             self.readline = readline
             sys.modules['readline'] = readline
 
             # Platform-specific configuration
             if os.name == 'nt':
                 # FIXME - check with Frederick to see if we can harmonize
                 # naming conventions with pyreadline to avoid this
                 # platform-dependent check
                 self.readline_startup_hook = readline.set_pre_input_hook
             else:
                 self.readline_startup_hook = readline.set_startup_hook
 
             # Load user's initrc file (readline config)
             # Or if libedit is used, load editrc.
             inputrc_name = os.environ.get('INPUTRC')
             if inputrc_name is None:
                 inputrc_name = '.inputrc'
                 if readline.uses_libedit:
                     inputrc_name = '.editrc'
                 inputrc_name = os.path.join(self.home_dir, inputrc_name)
             if os.path.isfile(inputrc_name):
                 try:
                     readline.read_init_file(inputrc_name)
                 except:
                     warn('Problems reading readline initialization file <%s>'
                          % inputrc_name)
 
             # Configure readline according to user's prefs
             # This is only done if GNU readline is being used.  If libedit
             # is being used (as on Leopard) the readline config is
             # not run as the syntax for libedit is different.
             if not readline.uses_libedit:
                 for rlcommand in self.readline_parse_and_bind:
                     #print "loading rl:",rlcommand  # dbg
                     readline.parse_and_bind(rlcommand)
 
             # Remove some chars from the delimiters list.  If we encounter
             # unicode chars, discard them.
             delims = readline.get_completer_delims()
             if not py3compat.PY3:
                 delims = delims.encode("ascii", "ignore")
             for d in self.readline_remove_delims:
                 delims = delims.replace(d, "")
             delims = delims.replace(ESC_MAGIC, '')
             readline.set_completer_delims(delims)
             # Store these so we can restore them if something like rpy2 modifies
             # them.
             self.readline_delims = delims
             # otherwise we end up with a monster history after a while:
             readline.set_history_length(self.history_length)
 
             self.refill_readline_hist()
             self.readline_no_record = ReadlineNoRecord(self)
 
         # Configure auto-indent for all platforms
         self.set_autoindent(self.autoindent)
 
     def refill_readline_hist(self):
         # Load the last 1000 lines from history
         self.readline.clear_history()
         stdin_encoding = sys.stdin.encoding or "utf-8"
         last_cell = u""
         for _, _, cell in self.history_manager.get_tail(1000,
                                                         include_latest=True):
             # Ignore blank lines and consecutive duplicates
             cell = cell.rstrip()
             if cell and (cell != last_cell):
                 try:
                     if self.multiline_history:
                           self.readline.add_history(py3compat.unicode_to_str(cell,
                                                                     stdin_encoding))
                     else:
                         for line in cell.splitlines():
                             self.readline.add_history(py3compat.unicode_to_str(line,
                                                                     stdin_encoding))
                     last_cell = cell
                 
                 except TypeError:
                     # The history DB can get corrupted so it returns strings
                     # containing null bytes, which readline objects to.
                     continue
 
     @skip_doctest
     def set_next_input(self, s):
         """ Sets the 'default' input string for the next command line.
 
         Requires readline.
 
         Example::
 
             In [1]: _ip.set_next_input("Hello Word")
             In [2]: Hello Word_  # cursor is here
         """
         self.rl_next_input = py3compat.cast_bytes_py2(s)
 
     # Maybe move this to the terminal subclass?
     def pre_readline(self):
         """readline hook to be used at the start of each line.
 
         Currently it handles auto-indent only."""
 
         if self.rl_do_indent:
             self.readline.insert_text(self._indent_current_str())
         if self.rl_next_input is not None:
             self.readline.insert_text(self.rl_next_input)
             self.rl_next_input = None
 
     def _indent_current_str(self):
         """return the current level of indentation as a string"""
         return self.input_splitter.indent_spaces * ' '
 
     #-------------------------------------------------------------------------
     # Things related to text completion
     #-------------------------------------------------------------------------
 
     def init_completer(self):
         """Initialize the completion machinery.
 
         This creates completion machinery that can be used by client code,
         either interactively in-process (typically triggered by the readline
         library), programatically (such as in test suites) or out-of-prcess
         (typically over the network by remote frontends).
         """
         from IPython.core.completer import IPCompleter
         from IPython.core.completerlib import (module_completer,
                 magic_run_completer, cd_completer, reset_completer)
 
         self.Completer = IPCompleter(shell=self,
                                      namespace=self.user_ns,
                                      global_namespace=self.user_global_ns,
                                      use_readline=self.has_readline,
                                      parent=self,
                                      )
         self.configurables.append(self.Completer)
 
         # Add custom completers to the basic ones built into IPCompleter
         sdisp = self.strdispatchers.get('complete_command', StrDispatch())
         self.strdispatchers['complete_command'] = sdisp
         self.Completer.custom_completers = sdisp
 
         self.set_hook('complete_command', module_completer, str_key = 'import')
         self.set_hook('complete_command', module_completer, str_key = 'from')
         self.set_hook('complete_command', magic_run_completer, str_key = '%run')
         self.set_hook('complete_command', cd_completer, str_key = '%cd')
         self.set_hook('complete_command', reset_completer, str_key = '%reset')
 
         # Only configure readline if we truly are using readline.  IPython can
         # do tab-completion over the network, in GUIs, etc, where readline
         # itself may be absent
         if self.has_readline:
             self.set_readline_completer()
 
     def complete(self, text, line=None, cursor_pos=None):
         """Return the completed text and a list of completions.
 
         Parameters
         ----------
 
            text : string
              A string of text to be completed on.  It can be given as empty and
              instead a line/position pair are given.  In this case, the
              completer itself will split the line like readline does.
 
            line : string, optional
              The complete line that text is part of.
 
            cursor_pos : int, optional
              The position of the cursor on the input line.
 
         Returns
         -------
           text : string
             The actual text that was completed.
 
           matches : list
             A sorted list with all possible completions.
 
         The optional arguments allow the completion to take more context into
         account, and are part of the low-level completion API.
 
         This is a wrapper around the completion mechanism, similar to what
         readline does at the command line when the TAB key is hit.  By
         exposing it as a method, it can be used by other non-readline
         environments (such as GUIs) for text completion.
 
         Simple usage example:
 
         In [1]: x = 'hello'
 
         In [2]: _ip.complete('x.l')
         Out[2]: ('x.l', ['x.ljust', 'x.lower', 'x.lstrip'])
         """
 
         # Inject names into __builtin__ so we can complete on the added names.
         with self.builtin_trap:
             return self.Completer.complete(text, line, cursor_pos)
 
     def set_custom_completer(self, completer, pos=0):
         """Adds a new custom completer function.
 
         The position argument (defaults to 0) is the index in the completers
         list where you want the completer to be inserted."""
 
         newcomp = types.MethodType(completer,self.Completer)
         self.Completer.matchers.insert(pos,newcomp)
 
     def set_readline_completer(self):
         """Reset readline's completer to be our own."""
         self.readline.set_completer(self.Completer.rlcomplete)
 
     def set_completer_frame(self, frame=None):
         """Set the frame of the completer."""
         if frame:
             self.Completer.namespace = frame.f_locals
             self.Completer.global_namespace = frame.f_globals
         else:
             self.Completer.namespace = self.user_ns
             self.Completer.global_namespace = self.user_global_ns
 
     #-------------------------------------------------------------------------
     # Things related to magics
     #-------------------------------------------------------------------------
 
     def init_magics(self):
         from IPython.core import magics as m
         self.magics_manager = magic.MagicsManager(shell=self,
                                    parent=self,
                                    user_magics=m.UserMagics(self))
         self.configurables.append(self.magics_manager)
 
         # Expose as public API from the magics manager
         self.register_magics = self.magics_manager.register
         self.define_magic = self.magics_manager.define_magic
 
         self.register_magics(m.AutoMagics, m.BasicMagics, m.CodeMagics,
             m.ConfigMagics, m.DeprecatedMagics, m.DisplayMagics, m.ExecutionMagics,
             m.ExtensionMagics, m.HistoryMagics, m.LoggingMagics,
             m.NamespaceMagics, m.OSMagics, m.PylabMagics, m.ScriptMagics,
         )
 
         # Register Magic Aliases
         mman = self.magics_manager
         # FIXME: magic aliases should be defined by the Magics classes
         # or in MagicsManager, not here
         mman.register_alias('ed', 'edit')
         mman.register_alias('hist', 'history')
         mman.register_alias('rep', 'recall')
         mman.register_alias('SVG', 'svg', 'cell')
         mman.register_alias('HTML', 'html', 'cell')
         mman.register_alias('file', 'writefile', 'cell')
 
         # FIXME: Move the color initialization to the DisplayHook, which
         # should be split into a prompt manager and displayhook. We probably
         # even need a centralize colors management object.
         self.magic('colors %s' % self.colors)
     
     # Defined here so that it's included in the documentation
     @functools.wraps(magic.MagicsManager.register_function)
     def register_magic_function(self, func, magic_kind='line', magic_name=None):
         self.magics_manager.register_function(func, 
                                   magic_kind=magic_kind, magic_name=magic_name)
 
     def run_line_magic(self, magic_name, line):
         """Execute the given line magic.
 
         Parameters
         ----------
         magic_name : str
           Name of the desired magic function, without '%' prefix.
 
         line : str
           The rest of the input line as a single string.
         """
         fn = self.find_line_magic(magic_name)
         if fn is None:
             cm = self.find_cell_magic(magic_name)
             etpl = "Line magic function `%%%s` not found%s."
             extra = '' if cm is None else (' (But cell magic `%%%%%s` exists, '
                                     'did you mean that instead?)' % magic_name )
             error(etpl % (magic_name, extra))
         else:
             # Note: this is the distance in the stack to the user's frame.
             # This will need to be updated if the internal calling logic gets
             # refactored, or else we'll be expanding the wrong variables.
             stack_depth = 2
             magic_arg_s = self.var_expand(line, stack_depth)
             # Put magic args in a list so we can call with f(*a) syntax
             args = [magic_arg_s]
             kwargs = {}
             # Grab local namespace if we need it:
             if getattr(fn, "needs_local_scope", False):
                 kwargs['local_ns'] = sys._getframe(stack_depth).f_locals
             with self.builtin_trap:
                 result = fn(*args,**kwargs)
             return result
 
     def run_cell_magic(self, magic_name, line, cell):
         """Execute the given cell magic.
         
         Parameters
         ----------
         magic_name : str
           Name of the desired magic function, without '%' prefix.
 
         line : str
           The rest of the first input line as a single string.
 
         cell : str
           The body of the cell as a (possibly multiline) string.
         """
         fn = self.find_cell_magic(magic_name)
         if fn is None:
             lm = self.find_line_magic(magic_name)
             etpl = "Cell magic `%%{0}` not found{1}."
             extra = '' if lm is None else (' (But line magic `%{0}` exists, '
                             'did you mean that instead?)'.format(magic_name))
             error(etpl.format(magic_name, extra))
         elif cell == '':
             message = '%%{0} is a cell magic, but the cell body is empty.'.format(magic_name)
             if self.find_line_magic(magic_name) is not None:
                 message += ' Did you mean the line magic %{0} (single %)?'.format(magic_name)
             raise UsageError(message)
         else:
             # Note: this is the distance in the stack to the user's frame.
             # This will need to be updated if the internal calling logic gets
             # refactored, or else we'll be expanding the wrong variables.
             stack_depth = 2
             magic_arg_s = self.var_expand(line, stack_depth)
             with self.builtin_trap:
                 result = fn(magic_arg_s, cell)
             return result
 
     def find_line_magic(self, magic_name):
         """Find and return a line magic by name.
 
         Returns None if the magic isn't found."""
         return self.magics_manager.magics['line'].get(magic_name)
 
     def find_cell_magic(self, magic_name):
         """Find and return a cell magic by name.
 
         Returns None if the magic isn't found."""
         return self.magics_manager.magics['cell'].get(magic_name)
 
     def find_magic(self, magic_name, magic_kind='line'):
         """Find and return a magic of the given type by name.
 
         Returns None if the magic isn't found."""
         return self.magics_manager.magics[magic_kind].get(magic_name)
 
     def magic(self, arg_s):
         """DEPRECATED. Use run_line_magic() instead.
 
         Call a magic function by name.
 
         Input: a string containing the name of the magic function to call and
         any additional arguments to be passed to the magic.
 
         magic('name -opt foo bar') is equivalent to typing at the ipython
         prompt:
 
         In[1]: %name -opt foo bar
 
         To call a magic without arguments, simply use magic('name').
 
         This provides a proper Python function to call IPython's magics in any
         valid Python code you can type at the interpreter, including loops and
         compound statements.
         """
         # TODO: should we issue a loud deprecation warning here?
         magic_name, _, magic_arg_s = arg_s.partition(' ')
         magic_name = magic_name.lstrip(prefilter.ESC_MAGIC)
         return self.run_line_magic(magic_name, magic_arg_s)
 
     #-------------------------------------------------------------------------
     # Things related to macros
     #-------------------------------------------------------------------------
 
     def define_macro(self, name, themacro):
         """Define a new macro
 
         Parameters
         ----------
         name : str
             The name of the macro.
         themacro : str or Macro
             The action to do upon invoking the macro.  If a string, a new
             Macro object is created by passing the string to it.
         """
 
         from IPython.core import macro
 
         if isinstance(themacro, string_types):
             themacro = macro.Macro(themacro)
         if not isinstance(themacro, macro.Macro):
             raise ValueError('A macro must be a string or a Macro instance.')
         self.user_ns[name] = themacro
 
     #-------------------------------------------------------------------------
     # Things related to the running of system commands
     #-------------------------------------------------------------------------
 
     def system_piped(self, cmd):
         """Call the given cmd in a subprocess, piping stdout/err
 
         Parameters
         ----------
         cmd : str
           Command to execute (can not end in '&', as background processes are
           not supported.  Should not be a command that expects input
           other than simple text.
         """
         if cmd.rstrip().endswith('&'):
             # this is *far* from a rigorous test
             # We do not support backgrounding processes because we either use
             # pexpect or pipes to read from.  Users can always just call
             # os.system() or use ip.system=ip.system_raw
             # if they really want a background process.
             raise OSError("Background processes not supported.")
 
         # we explicitly do NOT return the subprocess status code, because
         # a non-None value would trigger :func:`sys.displayhook` calls.
         # Instead, we store the exit_code in user_ns.
         self.user_ns['_exit_code'] = system(self.var_expand(cmd, depth=1))
 
     def system_raw(self, cmd):
         """Call the given cmd in a subprocess using os.system on Windows or
         subprocess.call using the system shell on other platforms.
 
         Parameters
         ----------
         cmd : str
           Command to execute.
         """
         cmd = self.var_expand(cmd, depth=1)
         # protect os.system from UNC paths on Windows, which it can't handle:
         if sys.platform == 'win32':
             from IPython.utils._process_win32 import AvoidUNCPath
             with AvoidUNCPath() as path:
                 if path is not None:
                     cmd = '"pushd %s &&"%s' % (path, cmd)
                 cmd = py3compat.unicode_to_str(cmd)
                 ec = os.system(cmd)
         else:
             cmd = py3compat.unicode_to_str(cmd)
             # Call the cmd using the OS shell, instead of the default /bin/sh, if set.
             ec = subprocess.call(cmd, shell=True, executable=os.environ.get('SHELL', None))
             # exit code is positive for program failure, or negative for
             # terminating signal number.
         
         # We explicitly do NOT return the subprocess status code, because
         # a non-None value would trigger :func:`sys.displayhook` calls.
         # Instead, we store the exit_code in user_ns.
         self.user_ns['_exit_code'] = ec
 
     # use piped system by default, because it is better behaved
     system = system_piped
 
     def getoutput(self, cmd, split=True, depth=0):
         """Get output (possibly including stderr) from a subprocess.
 
         Parameters
         ----------
         cmd : str
           Command to execute (can not end in '&', as background processes are
           not supported.
         split : bool, optional
           If True, split the output into an IPython SList.  Otherwise, an
           IPython LSString is returned.  These are objects similar to normal
           lists and strings, with a few convenience attributes for easier
           manipulation of line-based output.  You can use '?' on them for
           details.
         depth : int, optional
           How many frames above the caller are the local variables which should
           be expanded in the command string? The default (0) assumes that the
           expansion variables are in the stack frame calling this function.
         """
         if cmd.rstrip().endswith('&'):
             # this is *far* from a rigorous test
             raise OSError("Background processes not supported.")
         out = getoutput(self.var_expand(cmd, depth=depth+1))
         if split:
             out = SList(out.splitlines())
         else:
             out = LSString(out)
         return out
 
     #-------------------------------------------------------------------------
     # Things related to aliases
     #-------------------------------------------------------------------------
 
     def init_alias(self):
         self.alias_manager = AliasManager(shell=self, parent=self)
         self.configurables.append(self.alias_manager)
 
     #-------------------------------------------------------------------------
     # Things related to extensions
     #-------------------------------------------------------------------------
 
     def init_extension_manager(self):
         self.extension_manager = ExtensionManager(shell=self, parent=self)
         self.configurables.append(self.extension_manager)
 
     #-------------------------------------------------------------------------
     # Things related to payloads
     #-------------------------------------------------------------------------
 
     def init_payload(self):
         self.payload_manager = PayloadManager(parent=self)
         self.configurables.append(self.payload_manager)
     
     #-------------------------------------------------------------------------
     # Things related to widgets
     #-------------------------------------------------------------------------
     
     def init_comms(self):
         # not implemented in the base class
         pass
     
     #-------------------------------------------------------------------------
     # Things related to the prefilter
     #-------------------------------------------------------------------------
 
     def init_prefilter(self):
         self.prefilter_manager = PrefilterManager(shell=self, parent=self)
         self.configurables.append(self.prefilter_manager)
         # Ultimately this will be refactored in the new interpreter code, but
         # for now, we should expose the main prefilter method (there's legacy
         # code out there that may rely on this).
         self.prefilter = self.prefilter_manager.prefilter_lines
 
     def auto_rewrite_input(self, cmd):
         """Print to the screen the rewritten form of the user's command.
 
         This shows visual feedback by rewriting input lines that cause
         automatic calling to kick in, like::
 
           /f x
 
         into::
 
           ------> f(x)
 
         after the user's input prompt.  This helps the user understand that the
         input line was transformed automatically by IPython.
         """
         if not self.show_rewritten_input:
             return
         
         rw = self.prompt_manager.render('rewrite') + cmd
 
         try:
             # plain ascii works better w/ pyreadline, on some machines, so
             # we use it and only print uncolored rewrite if we have unicode
             rw = str(rw)
             print(rw, file=io.stdout)
         except UnicodeEncodeError:
             print("------> " + cmd)
 
     #-------------------------------------------------------------------------
     # Things related to extracting values/expressions from kernel and user_ns
     #-------------------------------------------------------------------------
 
     def _user_obj_error(self):
         """return simple exception dict
         
         for use in user_variables / expressions
         """
         
         etype, evalue, tb = self._get_exc_info()
         stb = self.InteractiveTB.get_exception_only(etype, evalue)
         
         exc_info = {
             u'status' : 'error',
             u'traceback' : stb,
             u'ename' : unicode_type(etype.__name__),
             u'evalue' : py3compat.safe_unicode(evalue),
         }
 
         return exc_info
     
     def _format_user_obj(self, obj):
         """format a user object to display dict
         
         for use in user_expressions / variables
         """
         
         data, md = self.display_formatter.format(obj)
         value = {
             'status' : 'ok',
             'data' : data,
             'metadata' : md,
         }
         return value
     
     def user_variables(self, names):
         """Get a list of variable names from the user's namespace.
 
         Parameters
         ----------
         names : list of strings
           A list of names of variables to be read from the user namespace.
 
         Returns
         -------
         A dict, keyed by the input names and with the rich mime-type repr(s) of each value.
         Each element will be a sub-dict of the same form as a display_data message.
         """
         out = {}
         user_ns = self.user_ns
         
         for varname in names:
             try:
                 value = self._format_user_obj(user_ns[varname])
             except:
                 value = self._user_obj_error()
             out[varname] = value
         return out
 
     def user_expressions(self, expressions):
         """Evaluate a dict of expressions in the user's namespace.
 
         Parameters
         ----------
         expressions : dict
           A dict with string keys and string values.  The expression values
           should be valid Python expressions, each of which will be evaluated
           in the user namespace.
 
         Returns
         -------
         A dict, keyed like the input expressions dict, with the rich mime-typed
         display_data of each value.
         """
         out = {}
         user_ns = self.user_ns
         global_ns = self.user_global_ns
         
         for key, expr in expressions.iteritems():
             try:
                 value = self._format_user_obj(eval(expr, global_ns, user_ns))
             except:
                 value = self._user_obj_error()
             out[key] = value
         return out
 
     #-------------------------------------------------------------------------
     # Things related to the running of code
     #-------------------------------------------------------------------------
 
     def ex(self, cmd):
         """Execute a normal python statement in user namespace."""
         with self.builtin_trap:
             exec(cmd, self.user_global_ns, self.user_ns)
 
     def ev(self, expr):
         """Evaluate python expression expr in user namespace.
 
         Returns the result of evaluation
         """
         with self.builtin_trap:
             return eval(expr, self.user_global_ns, self.user_ns)
 
     def safe_execfile(self, fname, *where, **kw):
         """A safe version of the builtin execfile().
 
         This version will never throw an exception, but instead print
         helpful error messages to the screen.  This only works on pure
         Python files with the .py extension.
 
         Parameters
         ----------
         fname : string
             The name of the file to be executed.
         where : tuple
             One or two namespaces, passed to execfile() as (globals,locals).
             If only one is given, it is passed as both.
         exit_ignore : bool (False)
             If True, then silence SystemExit for non-zero status (it is always
             silenced for zero status, as it is so common).
         raise_exceptions : bool (False)
             If True raise exceptions everywhere. Meant for testing.
 
         """
         kw.setdefault('exit_ignore', False)
         kw.setdefault('raise_exceptions', False)
 
         fname = os.path.abspath(os.path.expanduser(fname))
 
         # Make sure we can open the file
         try:
             with open(fname) as thefile:
                 pass
         except:
             warn('Could not open file <%s> for safe execution.' % fname)
             return
 
         # Find things also in current directory.  This is needed to mimic the
         # behavior of running a script from the system command line, where
         # Python inserts the script's directory into sys.path
         dname = os.path.dirname(fname)
 
         with prepended_to_syspath(dname):
             try:
                 py3compat.execfile(fname,*where)
             except SystemExit as status:
                 # If the call was made with 0 or None exit status (sys.exit(0)
                 # or sys.exit() ), don't bother showing a traceback, as both of
                 # these are considered normal by the OS:
                 # > python -c'import sys;sys.exit(0)'; echo $?
                 # 0
                 # > python -c'import sys;sys.exit()'; echo $?
                 # 0
                 # For other exit status, we show the exception unless
                 # explicitly silenced, but only in short form.
                 if kw['raise_exceptions']:
                     raise
                 if status.code and not kw['exit_ignore']:
                     self.showtraceback(exception_only=True)
             except:
                 if kw['raise_exceptions']:
                     raise
                 self.showtraceback()
 
     def safe_execfile_ipy(self, fname):
         """Like safe_execfile, but for .ipy files with IPython syntax.
 
         Parameters
         ----------
         fname : str
             The name of the file to execute.  The filename must have a
             .ipy extension.
         """
         fname = os.path.abspath(os.path.expanduser(fname))
 
         # Make sure we can open the file
         try:
             with open(fname) as thefile:
                 pass
         except:
             warn('Could not open file <%s> for safe execution.' % fname)
             return
 
         # Find things also in current directory.  This is needed to mimic the
         # behavior of running a script from the system command line, where
         # Python inserts the script's directory into sys.path
         dname = os.path.dirname(fname)
 
         with prepended_to_syspath(dname):
             try:
                 with open(fname) as thefile:
                     # self.run_cell currently captures all exceptions
                     # raised in user code.  It would be nice if there were
                     # versions of runlines, execfile that did raise, so
                     # we could catch the errors.
                     self.run_cell(thefile.read(), store_history=False, shell_futures=False)
             except:
                 self.showtraceback()
                 warn('Unknown failure executing file: <%s>' % fname)
 
     def safe_run_module(self, mod_name, where):
         """A safe version of runpy.run_module().
 
         This version will never throw an exception, but instead print
         helpful error messages to the screen.
 
         `SystemExit` exceptions with status code 0 or None are ignored.
 
         Parameters
         ----------
         mod_name : string
             The name of the module to be executed.
         where : dict
             The globals namespace.
         """
         try:
             try:
                 where.update(
                     runpy.run_module(str(mod_name), run_name="__main__",
                                      alter_sys=True)
                     )
             except SystemExit as status:
                 if status.code:
                     raise
         except:
             self.showtraceback()
             warn('Unknown failure executing module: <%s>' % mod_name)
 
     def _run_cached_cell_magic(self, magic_name, line):
         """Special method to call a cell magic with the data stored in self.
         """
         cell = self._current_cell_magic_body
         self._current_cell_magic_body = None
         return self.run_cell_magic(magic_name, line, cell)
 
     def run_cell(self, raw_cell, store_history=False, silent=False, shell_futures=True):
         """Run a complete IPython cell.
 
         Parameters
         ----------
         raw_cell : str
           The code (including IPython code such as %magic functions) to run.
         store_history : bool
           If True, the raw and translated cell will be stored in IPython's
           history. For user code calling back into IPython's machinery, this
           should be set to False.
         silent : bool
           If True, avoid side-effects, such as implicit displayhooks and
           and logging.  silent=True forces store_history=False.
         shell_futures : bool
           If True, the code will share future statements with the interactive
           shell. It will both be affected by previous __future__ imports, and
           any __future__ imports in the code will affect the shell. If False,
           __future__ imports are not shared in either direction.
         """
         if (not raw_cell) or raw_cell.isspace():
             return
         
         if silent:
             store_history = False
 
         self.input_transformer_manager.push(raw_cell)
         cell = self.input_transformer_manager.source_reset()
 
         # Our own compiler remembers the __future__ environment. If we want to
         # run code with a separate __future__ environment, use the default
         # compiler
         compiler = self.compile if shell_futures else CachingCompiler()
 
         with self.builtin_trap:
             prefilter_failed = False
             if len(cell.splitlines()) == 1:
                 try:
                     # use prefilter_lines to handle trailing newlines
                     # restore trailing newline for ast.parse
                     cell = self.prefilter_manager.prefilter_lines(cell) + '\n'
                 except AliasError as e:
                     error(e)
                     prefilter_failed = True
                 except Exception:
                     # don't allow prefilter errors to crash IPython
                     self.showtraceback()
                     prefilter_failed = True
 
             # Store raw and processed history
             if store_history:
                 self.history_manager.store_inputs(self.execution_count,
                                                   cell, raw_cell)
             if not silent:
                 self.logger.log(cell, raw_cell)
 
             if not prefilter_failed:
                 # don't run if prefilter failed
                 cell_name = self.compile.cache(cell, self.execution_count)
 
                 with self.display_trap:
                     try:
                         code_ast = compiler.ast_parse(cell, filename=cell_name)
                     except IndentationError:
                         self.showindentationerror()
                         if store_history:
                             self.execution_count += 1
                         return None
                     except (OverflowError, SyntaxError, ValueError, TypeError,
                             MemoryError):
                         self.showsyntaxerror()
                         if store_history:
                             self.execution_count += 1
                         return None
                     
                     code_ast = self.transform_ast(code_ast)
                     
                     interactivity = "none" if silent else self.ast_node_interactivity
                     self.run_ast_nodes(code_ast.body, cell_name,
                                        interactivity=interactivity, compiler=compiler)
                     
                     # Execute any registered post-execution functions.
                     # unless we are silent
                     post_exec = [] if silent else self._post_execute.iteritems()
                     
                     for func, status in post_exec:
                         if self.disable_failing_post_execute and not status:
                             continue
                         try:
                             func()
                         except KeyboardInterrupt:
                             print("\nKeyboardInterrupt", file=io.stderr)
                         except Exception:
                             # register as failing:
                             self._post_execute[func] = False
                             self.showtraceback()
                             print('\n'.join([
                                 "post-execution function %r produced an error." % func,
                                 "If this problem persists, you can disable failing post-exec functions with:",
                                 "",
                                 "    get_ipython().disable_failing_post_execute = True"
                             ]), file=io.stderr)
 
         if store_history:
             # Write output to the database. Does nothing unless
             # history output logging is enabled.
             self.history_manager.store_output(self.execution_count)
             # Each cell is a *single* input, regardless of how many lines it has
             self.execution_count += 1
     
     def transform_ast(self, node):
         """Apply the AST transformations from self.ast_transformers
         
         Parameters
         ----------
         node : ast.Node
           The root node to be transformed. Typically called with the ast.Module
           produced by parsing user input.
         
         Returns
         -------
         An ast.Node corresponding to the node it was called with. Note that it
         may also modify the passed object, so don't rely on references to the
         original AST.
         """
         for transformer in self.ast_transformers:
             try:
                 node = transformer.visit(node)
             except Exception:
                 warn("AST transformer %r threw an error. It will be unregistered." % transformer)
                 self.ast_transformers.remove(transformer)
         
         if self.ast_transformers:
             ast.fix_missing_locations(node)
         return node
                 
 
     def run_ast_nodes(self, nodelist, cell_name, interactivity='last_expr',
                         compiler=compile):
         """Run a sequence of AST nodes. The execution mode depends on the
         interactivity parameter.
 
         Parameters
         ----------
         nodelist : list
           A sequence of AST nodes to run.
         cell_name : str
           Will be passed to the compiler as the filename of the cell. Typically
           the value returned by ip.compile.cache(cell).
         interactivity : str
           'all', 'last', 'last_expr' or 'none', specifying which nodes should be
           run interactively (displaying output from expressions). 'last_expr'
           will run the last node interactively only if it is an expression (i.e.
           expressions in loops or other blocks are not displayed. Other values
           for this parameter will raise a ValueError.
         compiler : callable
           A function with the same interface as the built-in compile(), to turn
           the AST nodes into code objects. Default is the built-in compile().
         """
         if not nodelist:
             return
 
         if interactivity == 'last_expr':
             if isinstance(nodelist[-1], ast.Expr):
                 interactivity = "last"
             else:
                 interactivity = "none"
 
         if interactivity == 'none':
             to_run_exec, to_run_interactive = nodelist, []
         elif interactivity == 'last':
             to_run_exec, to_run_interactive = nodelist[:-1], nodelist[-1:]
         elif interactivity == 'all':
             to_run_exec, to_run_interactive = [], nodelist
         else:
             raise ValueError("Interactivity was %r" % interactivity)
 
         exec_count = self.execution_count
 
         try:
             for i, node in enumerate(to_run_exec):
                 mod = ast.Module([node])
                 code = compiler(mod, cell_name, "exec")
                 if self.run_code(code):
                     return True
 
             for i, node in enumerate(to_run_interactive):
                 mod = ast.Interactive([node])
                 code = compiler(mod, cell_name, "single")
                 if self.run_code(code):
                     return True
 
             # Flush softspace
             if softspace(sys.stdout, 0):
                 print()
 
         except:
             # It's possible to have exceptions raised here, typically by
             # compilation of odd code (such as a naked 'return' outside a
             # function) that did parse but isn't valid. Typically the exception
             # is a SyntaxError, but it's safest just to catch anything and show
             # the user a traceback.
 
             # We do only one try/except outside the loop to minimize the impact
             # on runtime, and also because if any node in the node list is
             # broken, we should stop execution completely.
             self.showtraceback()
 
         return False
 
     def run_code(self, code_obj):
         """Execute a code object.
 
         When an exception occurs, self.showtraceback() is called to display a
         traceback.
 
         Parameters
         ----------
         code_obj : code object
           A compiled code object, to be executed
 
         Returns
         -------
         False : successful execution.
         True : an error occurred.
         """
 
         # Set our own excepthook in case the user code tries to call it
         # directly, so that the IPython crash handler doesn't get triggered
         old_excepthook,sys.excepthook = sys.excepthook, self.excepthook
 
         # we save the original sys.excepthook in the instance, in case config
         # code (such as magics) needs access to it.
         self.sys_excepthook = old_excepthook
         outflag = 1  # happens in more places, so it's easier as default
         try:
             try:
                 self.hooks.pre_run_code_hook()
                 #rprint('Running code', repr(code_obj)) # dbg
                 exec(code_obj, self.user_global_ns, self.user_ns)
             finally:
                 # Reset our crash handler in place
                 sys.excepthook = old_excepthook
         except SystemExit:
             self.showtraceback(exception_only=True)
             warn("To exit: use 'exit', 'quit', or Ctrl-D.", level=1)
         except self.custom_exceptions:
             etype,value,tb = sys.exc_info()
             self.CustomTB(etype,value,tb)
         except:
             self.showtraceback()
         else:
             outflag = 0
         return outflag
 
     # For backwards compatibility
     runcode = run_code
 
     #-------------------------------------------------------------------------
     # Things related to GUI support and pylab
     #-------------------------------------------------------------------------
 
     def enable_gui(self, gui=None):
         raise NotImplementedError('Implement enable_gui in a subclass')
     
     def enable_matplotlib(self, gui=None):
         """Enable interactive matplotlib and inline figure support.
         
         This takes the following steps:
         
         1. select the appropriate eventloop and matplotlib backend
         2. set up matplotlib for interactive use with that backend
         3. configure formatters for inline figure display
         4. enable the selected gui eventloop
         
         Parameters
         ----------
         gui : optional, string
           If given, dictates the choice of matplotlib GUI backend to use
           (should be one of IPython's supported backends, 'qt', 'osx', 'tk',
           'gtk', 'wx' or 'inline'), otherwise we use the default chosen by
           matplotlib (as dictated by the matplotlib build-time options plus the
           user's matplotlibrc configuration file).  Note that not all backends
           make sense in all contexts, for example a terminal ipython can't
           display figures inline.
         """
         from IPython.core import pylabtools as pt
         gui, backend = pt.find_gui_and_backend(gui, self.pylab_gui_select)
     
         if gui != 'inline':
             # If we have our first gui selection, store it
             if self.pylab_gui_select is None:
                 self.pylab_gui_select = gui
             # Otherwise if they are different
             elif gui != self.pylab_gui_select:
                 print ('Warning: Cannot change to a different GUI toolkit: %s.'
                         ' Using %s instead.' % (gui, self.pylab_gui_select))
                 gui, backend = pt.find_gui_and_backend(self.pylab_gui_select)
         
         pt.activate_matplotlib(backend)
         pt.configure_inline_support(self, backend)
         
         # Now we must activate the gui pylab wants to use, and fix %run to take
         # plot updates into account
         self.enable_gui(gui)
         self.magics_manager.registry['ExecutionMagics'].default_runner = \
             pt.mpl_runner(self.safe_execfile)
         
         return gui, backend
 
     def enable_pylab(self, gui=None, import_all=True, welcome_message=False):
         """Activate pylab support at runtime.
 
         This turns on support for matplotlib, preloads into the interactive
         namespace all of numpy and pylab, and configures IPython to correctly
         interact with the GUI event loop.  The GUI backend to be used can be
         optionally selected with the optional ``gui`` argument.
         
         This method only adds preloading the namespace to InteractiveShell.enable_matplotlib.
 
         Parameters
         ----------
         gui : optional, string
           If given, dictates the choice of matplotlib GUI backend to use
           (should be one of IPython's supported backends, 'qt', 'osx', 'tk',
           'gtk', 'wx' or 'inline'), otherwise we use the default chosen by
           matplotlib (as dictated by the matplotlib build-time options plus the
           user's matplotlibrc configuration file).  Note that not all backends
           make sense in all contexts, for example a terminal ipython can't
           display figures inline.
         import_all : optional, bool, default: True
           Whether to do `from numpy import *` and `from pylab import *`
           in addition to module imports.
         welcome_message : deprecated
           This argument is ignored, no welcome message will be displayed.
         """
         from IPython.core.pylabtools import import_pylab
         
         gui, backend = self.enable_matplotlib(gui)
         
         # We want to prevent the loading of pylab to pollute the user's
         # namespace as shown by the %who* magics, so we execute the activation
         # code in an empty namespace, and we update *both* user_ns and
         # user_ns_hidden with this information.
         ns = {}
         import_pylab(ns, import_all)
         # warn about clobbered names
         ignored = set(["__builtins__"])
         both = set(ns).intersection(self.user_ns).difference(ignored)
         clobbered = [ name for name in both if self.user_ns[name] is not ns[name] ]
         self.user_ns.update(ns)
         self.user_ns_hidden.update(ns)
         return gui, backend, clobbered
 
     #-------------------------------------------------------------------------
     # Utilities
     #-------------------------------------------------------------------------
 
     def var_expand(self, cmd, depth=0, formatter=DollarFormatter()):
         """Expand python variables in a string.
 
         The depth argument indicates how many frames above the caller should
         be walked to look for the local namespace where to expand variables.
 
         The global namespace for expansion is always the user's interactive
         namespace.
         """
         ns = self.user_ns.copy()
         ns.update(sys._getframe(depth+1).f_locals)
         try:
             # We have to use .vformat() here, because 'self' is a valid and common
             # name, and expanding **ns for .format() would make it collide with
             # the 'self' argument of the method.
             cmd = formatter.vformat(cmd, args=[], kwargs=ns)
         except Exception:
             # if formatter couldn't format, just let it go untransformed
             pass
         return cmd
 
     def mktempfile(self, data=None, prefix='ipython_edit_'):
         """Make a new tempfile and return its filename.
 
         This makes a call to tempfile.mktemp, but it registers the created
         filename internally so ipython cleans it up at exit time.
 
         Optional inputs:
 
           - data(None): if data is given, it gets written out to the temp file
             immediately, and the file is closed again."""
 
         filename = tempfile.mktemp('.py', prefix)
         self.tempfiles.append(filename)
 
         if data:
             tmp_file = open(filename,'w')
             tmp_file.write(data)
             tmp_file.close()
         return filename
 
     # TODO:  This should be removed when Term is refactored.
     def write(self,data):
         """Write a string to the default output"""
         io.stdout.write(data)
 
     # TODO:  This should be removed when Term is refactored.
     def write_err(self,data):
         """Write a string to the default error output"""
         io.stderr.write(data)
 
     def ask_yes_no(self, prompt, default=None):
         if self.quiet:
             return True
         return ask_yes_no(prompt,default)
 
     def show_usage(self):
         """Show a usage message"""
         page.page(IPython.core.usage.interactive_usage)
 
     def extract_input_lines(self, range_str, raw=False):
         """Return as a string a set of input history slices.
 
         Parameters
         ----------
         range_str : string
             The set of slices is given as a string, like "~5/6-~4/2 4:8 9",
             since this function is for use by magic functions which get their
             arguments as strings. The number before the / is the session
             number: ~n goes n back from the current session.
 
         Optional Parameters:
           - raw(False): by default, the processed input is used.  If this is
             true, the raw input history is used instead.
 
         Note that slices can be called with two notations:
 
         N:M -> standard python form, means including items N...(M-1).
 
         N-M -> include items N..M (closed endpoint).
         """
         lines = self.history_manager.get_range_by_str(range_str, raw=raw)
         return "\n".join(x for _, _, x in lines)
 
     def find_user_code(self, target, raw=True, py_only=False, skip_encoding_cookie=True):
         """Get a code string from history, file, url, or a string or macro.
 
         This is mainly used by magic functions.
 
         Parameters
         ----------
 
         target : str
 
           A string specifying code to retrieve. This will be tried respectively
           as: ranges of input history (see %history for syntax), url,
           correspnding .py file, filename, or an expression evaluating to a
           string or Macro in the user namespace.
 
         raw : bool
           If true (default), retrieve raw history. Has no effect on the other
           retrieval mechanisms.
 
         py_only : bool (default False)
           Only try to fetch python code, do not try alternative methods to decode file
           if unicode fails.
 
         Returns
         -------
         A string of code.
 
         ValueError is raised if nothing is found, and TypeError if it evaluates
         to an object of another type. In each case, .args[0] is a printable
         message.
         """
         code = self.extract_input_lines(target, raw=raw)  # Grab history
         if code:
             return code
         utarget = unquote_filename(target)
         try:
             if utarget.startswith(('http://', 'https://')):
                 return openpy.read_py_url(utarget, skip_encoding_cookie=skip_encoding_cookie)
         except UnicodeDecodeError:
             if not py_only :
                 from urllib import urlopen  # Deferred import
                 response = urlopen(target)
                 return response.read().decode('latin1')
             raise ValueError(("'%s' seem to be unreadable.") % utarget)
 
         potential_target = [target]
         try :
             potential_target.insert(0,get_py_filename(target))
         except IOError:
             pass
 
         for tgt in potential_target :
             if os.path.isfile(tgt):                        # Read file
                 try :
                     return openpy.read_py_file(tgt, skip_encoding_cookie=skip_encoding_cookie)
                 except UnicodeDecodeError :
                     if not py_only :
                         with io_open(tgt,'r', encoding='latin1') as f :
                             return f.read()
                     raise ValueError(("'%s' seem to be unreadable.") % target)
             elif os.path.isdir(os.path.expanduser(tgt)):
                 raise ValueError("'%s' is a directory, not a regular file." % target)
 
         try:                                              # User namespace
             codeobj = eval(target, self.user_ns)
         except Exception:
             raise ValueError(("'%s' was not found in history, as a file, url, "
                                 "nor in the user namespace.") % target)
         if isinstance(codeobj, string_types):
             return codeobj
         elif isinstance(codeobj, Macro):
             return codeobj.value
 
         raise TypeError("%s is neither a string nor a macro." % target,
                         codeobj)
 
     #-------------------------------------------------------------------------
     # Things related to IPython exiting
     #-------------------------------------------------------------------------
     def atexit_operations(self):
         """This will be executed at the time of exit.
 
         Cleanup operations and saving of persistent data that is done
         unconditionally by IPython should be performed here.
 
         For things that may depend on startup flags or platform specifics (such
         as having readline or not), register a separate atexit function in the
         code that has the appropriate information, rather than trying to
         clutter
         """
         # Close the history session (this stores the end time and line count)
         # this must be *before* the tempfile cleanup, in case of temporary
         # history db
         self.history_manager.end_session()
 
         # Cleanup all tempfiles left around
         for tfile in self.tempfiles:
             try:
                 os.unlink(tfile)
             except OSError:
                 pass
 
         # Clear all user namespaces to release all references cleanly.
         self.reset(new_session=False)
 
         # Run user hooks
         self.hooks.shutdown_hook()
 
     def cleanup(self):
         self.restore_sys_module_state()
 
 
-class InteractiveShellABC(object):
+class InteractiveShellABC(with_metaclass(abc.ABCMeta, object)):
     """An abstract base class for InteractiveShell."""
-    __metaclass__ = abc.ABCMeta
 
 InteractiveShellABC.register(InteractiveShell)

IPython/kernel/channelsabc.py

@@ -1,126 +1,125 b''
 """Abstract base classes for kernel client channels"""
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2013  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
-# Standard library imports
 import abc
 
+from IPython.utils.py3compat import with_metaclass
+
 #-----------------------------------------------------------------------------
 # Channels
 #-----------------------------------------------------------------------------
 
 
-class ChannelABC(object):
+class ChannelABC(with_metaclass(abc.ABCMeta, object)):
     """A base class for all channel ABCs."""
 
-    __metaclass__ = abc.ABCMeta
-
     @abc.abstractmethod
     def start(self):
         pass
 
     @abc.abstractmethod
     def stop(self):
         pass
 
     @abc.abstractmethod
     def is_alive(self):
         pass
 
 
 class ShellChannelABC(ChannelABC):
     """ShellChannel ABC.
 
     The docstrings for this class can be found in the base implementation:
 
     `IPython.kernel.channels.ShellChannel`
     """
 
     @abc.abstractproperty
     def allow_stdin(self):
         pass
 
     @abc.abstractmethod
     def execute(self, code, silent=False, store_history=True,
                 user_variables=None, user_expressions=None, allow_stdin=None):
         pass
 
     @abc.abstractmethod
     def complete(self, text, line, cursor_pos, block=None):
         pass
 
     @abc.abstractmethod
     def object_info(self, oname, detail_level=0):
         pass
 
     @abc.abstractmethod
     def history(self, raw=True, output=False, hist_access_type='range', **kwargs):
         pass
 
     @abc.abstractmethod
     def kernel_info(self):
         pass
 
     @abc.abstractmethod
     def shutdown(self, restart=False):
         pass
 
 
 class IOPubChannelABC(ChannelABC):
     """IOPubChannel ABC.
 
     The docstrings for this class can be found in the base implementation:
 
     `IPython.kernel.channels.IOPubChannel`
     """
 
     @abc.abstractmethod
     def flush(self, timeout=1.0):
         pass
 
 
 class StdInChannelABC(ChannelABC):
     """StdInChannel ABC.
 
     The docstrings for this class can be found in the base implementation:
 
     `IPython.kernel.channels.StdInChannel`
     """
 
     @abc.abstractmethod
     def input(self, string):
         pass
 
 
 class HBChannelABC(ChannelABC):
     """HBChannel ABC.
 
     The docstrings for this class can be found in the base implementation:
 
     `IPython.kernel.channels.HBChannel`
     """
 
     @abc.abstractproperty
     def time_to_dead(self):
         pass
 
     @abc.abstractmethod
     def pause(self):
         pass
 
     @abc.abstractmethod
     def unpause(self):
         pass
 
     @abc.abstractmethod
     def is_beating(self):
         pass

IPython/kernel/clientabc.py

@@ -1,81 +1,80 b''
 """Abstract base class for kernel clients"""
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2013  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
-# Standard library imports
 import abc
 
+from IPython.utils.py3compat import with_metaclass
+
 #-----------------------------------------------------------------------------
 # Main kernel client class
 #-----------------------------------------------------------------------------
 
-class KernelClientABC(object):
+class KernelClientABC(with_metaclass(abc.ABCMeta, object)):
     """KernelManager ABC.
 
     The docstrings for this class can be found in the base implementation:
 
     `IPython.kernel.client.KernelClient`
     """
 
-    __metaclass__ = abc.ABCMeta
-
     @abc.abstractproperty
     def kernel(self):
         pass
 
     @abc.abstractproperty
     def shell_channel_class(self):
         pass
 
     @abc.abstractproperty
     def iopub_channel_class(self):
         pass
 
     @abc.abstractproperty
     def hb_channel_class(self):
         pass
 
     @abc.abstractproperty
     def stdin_channel_class(self):
         pass
 
     #--------------------------------------------------------------------------
     # Channel management methods
     #--------------------------------------------------------------------------
 
     @abc.abstractmethod
     def start_channels(self, shell=True, iopub=True, stdin=True, hb=True):
         pass
 
     @abc.abstractmethod
     def stop_channels(self):
         pass
 
     @abc.abstractproperty
     def channels_running(self):
         pass
 
     @abc.abstractproperty
     def shell_channel(self):
         pass
 
     @abc.abstractproperty
     def iopub_channel(self):
         pass
 
     @abc.abstractproperty
     def stdin_channel(self):
         pass
 
     @abc.abstractproperty
     def hb_channel(self):
         pass

IPython/kernel/inprocess/socket.py

@@ -1,66 +1,65 b''
 """ Defines a dummy socket implementing (part of) the zmq.Socket interface. """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2012  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 # Standard library imports.
 import abc
 try:
     from queue import Queue  # Py 3
 except ImportError:
     from Queue import Queue  # Py 2
 
 # System library imports.
 import zmq
 
 # Local imports.
 from IPython.utils.traitlets import HasTraits, Instance, Int
+from IPython.utils.py3compat import with_metaclass
 
 #-----------------------------------------------------------------------------
 # Generic socket interface
 #-----------------------------------------------------------------------------
 
-class SocketABC(object):
-    __metaclass__ = abc.ABCMeta
-
+class SocketABC(with_metaclass(abc.ABCMeta, object)):
     @abc.abstractmethod
     def recv_multipart(self, flags=0, copy=True, track=False):
         raise NotImplementedError
 
     @abc.abstractmethod
     def send_multipart(self, msg_parts, flags=0, copy=True, track=False):
         raise NotImplementedError
 
 SocketABC.register(zmq.Socket)
 
 #-----------------------------------------------------------------------------
 # Dummy socket class
 #-----------------------------------------------------------------------------
 
 class DummySocket(HasTraits):
     """ A dummy socket implementing (part of) the zmq.Socket interface. """
     
     queue = Instance(Queue, ())
     message_sent = Int(0) # Should be an Event
 
     #-------------------------------------------------------------------------
     # Socket interface
     #-------------------------------------------------------------------------
 
     def recv_multipart(self, flags=0, copy=True, track=False):
         return self.queue.get_nowait()
 
     def send_multipart(self, msg_parts, flags=0, copy=True, track=False):
         msg_parts = map(zmq.Message, msg_parts)
         self.queue.put_nowait(msg_parts)
         self.message_sent += 1
 
 SocketABC.register(DummySocket)

IPython/kernel/managerabc.py

@@ -1,225 +1,222 b''
 """Abstract base classes for kernel manager and channels."""
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2013  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
-# Standard library imports.
 import abc
 
+from IPython.utils.py3compat import with_metaclass
+
 #-----------------------------------------------------------------------------
 # Channels
 #-----------------------------------------------------------------------------
 
 
-class ChannelABC(object):
+class ChannelABC(with_metaclass(abc.ABCMeta, object)):
     """A base class for all channel ABCs."""
 
-    __metaclass__ = abc.ABCMeta
-
     @abc.abstractmethod
     def start(self):
         pass
 
     @abc.abstractmethod
     def stop(self):
         pass
 
     @abc.abstractmethod
     def is_alive(self):
         pass
 
 
 class ShellChannelABC(ChannelABC):
     """ShellChannel ABC.
 
     The docstrings for this class can be found in the base implementation:
 
     `IPython.kernel.kernelmanager.ShellChannel`
     """
 
     @abc.abstractproperty
     def allow_stdin(self):
         pass
 
     @abc.abstractmethod
     def execute(self, code, silent=False, store_history=True,
                 user_variables=None, user_expressions=None, allow_stdin=None):
         pass
 
     @abc.abstractmethod
     def complete(self, text, line, cursor_pos, block=None):
         pass
 
     @abc.abstractmethod
     def object_info(self, oname, detail_level=0):
         pass
 
     @abc.abstractmethod
     def history(self, raw=True, output=False, hist_access_type='range', **kwargs):
         pass
 
     @abc.abstractmethod
     def kernel_info(self):
         pass
 
     @abc.abstractmethod
     def shutdown(self, restart=False):
         pass
 
 
 class IOPubChannelABC(ChannelABC):
     """IOPubChannel ABC.
 
     The docstrings for this class can be found in the base implementation:
 
     `IPython.kernel.kernelmanager.IOPubChannel`
     """
 
     @abc.abstractmethod
     def flush(self, timeout=1.0):
         pass
 
 
 class StdInChannelABC(ChannelABC):
     """StdInChannel ABC.
 
     The docstrings for this class can be found in the base implementation:
 
     `IPython.kernel.kernelmanager.StdInChannel`
     """
 
     @abc.abstractmethod
     def input(self, string):
         pass
 
 
 class HBChannelABC(ChannelABC):
     """HBChannel ABC.
 
     The docstrings for this class can be found in the base implementation:
 
     `IPython.kernel.kernelmanager.HBChannel`
     """
 
     @abc.abstractproperty
     def time_to_dead(self):
         pass
 
     @abc.abstractmethod
     def pause(self):
         pass
 
     @abc.abstractmethod
     def unpause(self):
         pass
 
     @abc.abstractmethod
     def is_beating(self):
         pass
 
 
 #-----------------------------------------------------------------------------
 # Main kernel manager class
 #-----------------------------------------------------------------------------
 
-class KernelManagerABC(object):
+class KernelManagerABC(with_metaclass(abc.ABCMeta, object)):
     """KernelManager ABC.
 
     The docstrings for this class can be found in the base implementation:
 
     `IPython.kernel.kernelmanager.KernelManager`
     """
 
-    __metaclass__ = abc.ABCMeta
-
     @abc.abstractproperty
     def kernel(self):
         pass
 
     @abc.abstractproperty
     def shell_channel_class(self):
         pass
 
     @abc.abstractproperty
     def iopub_channel_class(self):
         pass
 
     @abc.abstractproperty
     def hb_channel_class(self):
         pass
 
     @abc.abstractproperty
     def stdin_channel_class(self):
         pass
 
     #--------------------------------------------------------------------------
     # Channel management methods
     #--------------------------------------------------------------------------
 
     @abc.abstractmethod
     def start_channels(self, shell=True, iopub=True, stdin=True, hb=True):
         pass
 
     @abc.abstractmethod
     def stop_channels(self):
         pass
 
     @abc.abstractproperty
     def channels_running(self):
         pass
 
     @abc.abstractproperty
     def shell_channel(self):
         pass
 
     @abc.abstractproperty
     def iopub_channel(self):
         pass
 
     @abc.abstractproperty
     def stdin_channel(self):
         pass
 
     @abc.abstractproperty
     def hb_channel(self):
         pass
 
     #--------------------------------------------------------------------------
     # Kernel management
     #--------------------------------------------------------------------------
 
     @abc.abstractmethod
     def start_kernel(self, **kw):
         pass
 
     @abc.abstractmethod
     def shutdown_kernel(self, now=False, restart=False):
         pass
 
     @abc.abstractmethod
     def restart_kernel(self, now=False, **kw):
         pass
 
     @abc.abstractproperty
     def has_kernel(self):
         pass
 
     @abc.abstractmethod
     def interrupt_kernel(self):
         pass
 
     @abc.abstractmethod
     def signal_kernel(self, signum):
         pass
 
     @abc.abstractmethod
     def is_alive(self):
         pass

IPython/qt/console/console_widget.py

@@ -1,2110 +1,2110 b''
 """ An abstract base class for console-type widgets.
 """
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 # Standard library imports
 import os.path
 import re
 import sys
 from textwrap import dedent
 import time
 from unicodedata import category
 import webbrowser
 
 # System library imports
 from IPython.external.qt import QtCore, QtGui
 
 # Local imports
 from IPython.config.configurable import LoggingConfigurable
 from IPython.core.inputsplitter import ESC_SEQUENCES
 from IPython.qt.rich_text import HtmlExporter
 from IPython.qt.util import MetaQObjectHasTraits, get_font
+from IPython.utils.py3compat import with_metaclass
 from IPython.utils.text import columnize
 from IPython.utils.traitlets import Bool, Enum, Integer, Unicode
 from .ansi_code_processor import QtAnsiCodeProcessor
 from .completion_widget import CompletionWidget
 from .completion_html import CompletionHtml
 from .completion_plain import CompletionPlain
 from .kill_ring import QtKillRing
 
 
 #-----------------------------------------------------------------------------
 # Functions
 #-----------------------------------------------------------------------------
 
 ESCAPE_CHARS = ''.join(ESC_SEQUENCES)
 ESCAPE_RE = re.compile("^["+ESCAPE_CHARS+"]+")
 
 def commonprefix(items):
     """Get common prefix for completions
 
     Return the longest common prefix of a list of strings, but with special
     treatment of escape characters that might precede commands in IPython,
     such as %magic functions. Used in tab completion.
 
     For a more general function, see os.path.commonprefix
     """
     # the last item will always have the least leading % symbol
     # min / max are first/last in alphabetical order
     first_match  = ESCAPE_RE.match(min(items))
     last_match  = ESCAPE_RE.match(max(items))
     # common suffix is (common prefix of reversed items) reversed
     if first_match and last_match:
         prefix = os.path.commonprefix((first_match.group(0)[::-1], last_match.group(0)[::-1]))[::-1]
     else:
         prefix = ''
 
     items = [s.lstrip(ESCAPE_CHARS) for s in items]
     return prefix+os.path.commonprefix(items)
 
 def is_letter_or_number(char):
     """ Returns whether the specified unicode character is a letter or a number.
     """
     cat = category(char)
     return cat.startswith('L') or cat.startswith('N')
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 
-class ConsoleWidget(LoggingConfigurable, QtGui.QWidget):
+class ConsoleWidget(with_metaclass(MetaQObjectHasTraits, type('NewBase', (LoggingConfigurable, QtGui.QWidget), {}))):
     """ An abstract base class for console-type widgets. This class has
         functionality for:
 
             * Maintaining a prompt and editing region
             * Providing the traditional Unix-style console keyboard shortcuts
             * Performing tab completion
             * Paging text
             * Handling ANSI escape codes
 
         ConsoleWidget also provides a number of utility methods that will be
         convenient to implementors of a console-style widget.
     """
-    __metaclass__ = MetaQObjectHasTraits
 
     #------ Configuration ------------------------------------------------------
 
     ansi_codes = Bool(True, config=True,
         help="Whether to process ANSI escape codes."
     )
     buffer_size = Integer(500, config=True,
         help="""
         The maximum number of lines of text before truncation. Specifying a
         non-positive number disables text truncation (not recommended).
         """
     )
     execute_on_complete_input = Bool(True, config=True,
         help="""Whether to automatically execute on syntactically complete input.
         
         If False, Shift-Enter is required to submit each execution.
         Disabling this is mainly useful for non-Python kernels,
         where the completion check would be wrong.
         """
     )
     gui_completion = Enum(['plain', 'droplist', 'ncurses'], config=True,
                     default_value = 'ncurses',
                     help="""
                     The type of completer to use. Valid values are:
 
                     'plain'   : Show the available completion as a text list
                                 Below the editing area.
                     'droplist': Show the completion in a drop down list navigable
                                 by the arrow keys, and from which you can select
                                 completion by pressing Return.
                     'ncurses' : Show the completion as a text list which is navigable by
                                 `tab` and arrow keys.
                     """
     )
     # NOTE: this value can only be specified during initialization.
     kind = Enum(['plain', 'rich'], default_value='plain', config=True,
         help="""
         The type of underlying text widget to use. Valid values are 'plain',
         which specifies a QPlainTextEdit, and 'rich', which specifies a
         QTextEdit.
         """
     )
     # NOTE: this value can only be specified during initialization.
     paging = Enum(['inside', 'hsplit', 'vsplit', 'custom', 'none'],
                   default_value='inside', config=True,
         help="""
         The type of paging to use. Valid values are:
 
             'inside' : The widget pages like a traditional terminal.
             'hsplit' : When paging is requested, the widget is split
                        horizontally. The top pane contains the console, and the
                        bottom pane contains the paged text.
             'vsplit' : Similar to 'hsplit', except that a vertical splitter
                        used.
             'custom' : No action is taken by the widget beyond emitting a
                        'custom_page_requested(str)' signal.
             'none'   : The text is written directly to the console.
         """)
 
     font_family = Unicode(config=True,
         help="""The font family to use for the console.
         On OSX this defaults to Monaco, on Windows the default is
         Consolas with fallback of Courier, and on other platforms
         the default is Monospace.
         """)
     def _font_family_default(self):
         if sys.platform == 'win32':
             # Consolas ships with Vista/Win7, fallback to Courier if needed
             return 'Consolas'
         elif sys.platform == 'darwin':
             # OSX always has Monaco, no need for a fallback
             return 'Monaco'
         else:
             # Monospace should always exist, no need for a fallback
             return 'Monospace'
 
     font_size = Integer(config=True,
         help="""The font size. If unconfigured, Qt will be entrusted
         with the size of the font.
         """)
 
     width = Integer(81, config=True,
         help="""The width of the console at start time in number
         of characters (will double with `hsplit` paging)
         """)
 
     height = Integer(25, config=True,
         help="""The height of the console at start time in number
         of characters (will double with `vsplit` paging)
         """)
 
     # Whether to override ShortcutEvents for the keybindings defined by this
     # widget (Ctrl+n, Ctrl+a, etc). Enable this if you want this widget to take
     # priority (when it has focus) over, e.g., window-level menu shortcuts.
     override_shortcuts = Bool(False)
     
     # ------ Custom Qt Widgets -------------------------------------------------
     
     # For other projects to easily override the Qt widgets used by the console
     # (e.g. Spyder)
     custom_control = None
     custom_page_control = None
 
     #------ Signals ------------------------------------------------------------
 
     # Signals that indicate ConsoleWidget state.
     copy_available = QtCore.Signal(bool)
     redo_available = QtCore.Signal(bool)
     undo_available = QtCore.Signal(bool)
 
     # Signal emitted when paging is needed and the paging style has been
     # specified as 'custom'.
     custom_page_requested = QtCore.Signal(object)
 
     # Signal emitted when the font is changed.
     font_changed = QtCore.Signal(QtGui.QFont)
 
     #------ Protected class variables ------------------------------------------
 
     # control handles
     _control = None
     _page_control = None
     _splitter = None
 
     # When the control key is down, these keys are mapped.
     _ctrl_down_remap = { QtCore.Qt.Key_B : QtCore.Qt.Key_Left,
                          QtCore.Qt.Key_F : QtCore.Qt.Key_Right,
                          QtCore.Qt.Key_A : QtCore.Qt.Key_Home,
                          QtCore.Qt.Key_P : QtCore.Qt.Key_Up,
                          QtCore.Qt.Key_N : QtCore.Qt.Key_Down,
                          QtCore.Qt.Key_H : QtCore.Qt.Key_Backspace, }
     if not sys.platform == 'darwin':
         # On OS X, Ctrl-E already does the right thing, whereas End moves the
         # cursor to the bottom of the buffer.
         _ctrl_down_remap[QtCore.Qt.Key_E] = QtCore.Qt.Key_End
 
     # The shortcuts defined by this widget. We need to keep track of these to
     # support 'override_shortcuts' above.
     _shortcuts = set(_ctrl_down_remap.keys() +
                      [ QtCore.Qt.Key_C, QtCore.Qt.Key_G, QtCore.Qt.Key_O,
                        QtCore.Qt.Key_V ])
 
     _temp_buffer_filled = False
 
     #---------------------------------------------------------------------------
     # 'QObject' interface
     #---------------------------------------------------------------------------
 
     def __init__(self, parent=None, **kw):
         """ Create a ConsoleWidget.
 
         Parameters:
         -----------
         parent : QWidget, optional [default None]
             The parent for this widget.
         """
         QtGui.QWidget.__init__(self, parent)
         LoggingConfigurable.__init__(self, **kw)
 
         # While scrolling the pager on Mac OS X, it tears badly.  The
         # NativeGesture is platform and perhaps build-specific hence
         # we take adequate precautions here.
         self._pager_scroll_events = [QtCore.QEvent.Wheel]
         if hasattr(QtCore.QEvent, 'NativeGesture'):
             self._pager_scroll_events.append(QtCore.QEvent.NativeGesture)
 
         # Create the layout and underlying text widget.
         layout = QtGui.QStackedLayout(self)
         layout.setContentsMargins(0, 0, 0, 0)
         self._control = self._create_control()
         if self.paging in ('hsplit', 'vsplit'):
             self._splitter = QtGui.QSplitter()
             if self.paging == 'hsplit':
                 self._splitter.setOrientation(QtCore.Qt.Horizontal)
             else:
                 self._splitter.setOrientation(QtCore.Qt.Vertical)
             self._splitter.addWidget(self._control)
             layout.addWidget(self._splitter)
         else:
             layout.addWidget(self._control)
 
         # Create the paging widget, if necessary.
         if self.paging in ('inside', 'hsplit', 'vsplit'):
             self._page_control = self._create_page_control()
             if self._splitter:
                 self._page_control.hide()
                 self._splitter.addWidget(self._page_control)
             else:
                 layout.addWidget(self._page_control)
 
         # Initialize protected variables. Some variables contain useful state
         # information for subclasses; they should be considered read-only.
         self._append_before_prompt_pos = 0
         self._ansi_processor = QtAnsiCodeProcessor()
         if self.gui_completion == 'ncurses':
             self._completion_widget = CompletionHtml(self)
         elif self.gui_completion == 'droplist':
             self._completion_widget = CompletionWidget(self)
         elif self.gui_completion == 'plain':
             self._completion_widget = CompletionPlain(self)
 
         self._continuation_prompt = '> '
         self._continuation_prompt_html = None
         self._executing = False
         self._filter_resize = False
         self._html_exporter = HtmlExporter(self._control)
         self._input_buffer_executing = ''
         self._input_buffer_pending = ''
         self._kill_ring = QtKillRing(self._control)
         self._prompt = ''
         self._prompt_html = None
         self._prompt_pos = 0
         self._prompt_sep = ''
         self._reading = False
         self._reading_callback = None
         self._tab_width = 8
 
         # List of strings pending to be appended as plain text in the widget.
         # The text is not immediately inserted when available to not
         # choke the Qt event loop with paint events for the widget in
         # case of lots of output from kernel.
         self._pending_insert_text = []
 
         # Timer to flush the pending stream messages. The interval is adjusted
         # later based on actual time taken for flushing a screen (buffer_size)
         # of output text.
         self._pending_text_flush_interval = QtCore.QTimer(self._control)
         self._pending_text_flush_interval.setInterval(100)
         self._pending_text_flush_interval.setSingleShot(True)
         self._pending_text_flush_interval.timeout.connect(
                                             self._flush_pending_stream)
 
         # Set a monospaced font.
         self.reset_font()
 
         # Configure actions.
         action = QtGui.QAction('Print', None)
         action.setEnabled(True)
         printkey = QtGui.QKeySequence(QtGui.QKeySequence.Print)
         if printkey.matches("Ctrl+P") and sys.platform != 'darwin':
             # Only override the default if there is a collision.
             # Qt ctrl = cmd on OSX, so the match gets a false positive on OSX.
             printkey = "Ctrl+Shift+P"
         action.setShortcut(printkey)
         action.setShortcutContext(QtCore.Qt.WidgetWithChildrenShortcut)
         action.triggered.connect(self.print_)
         self.addAction(action)
         self.print_action = action
 
         action = QtGui.QAction('Save as HTML/XML', None)
         action.setShortcut(QtGui.QKeySequence.Save)
         action.setShortcutContext(QtCore.Qt.WidgetWithChildrenShortcut)
         action.triggered.connect(self.export_html)
         self.addAction(action)
         self.export_action = action
 
         action = QtGui.QAction('Select All', None)
         action.setEnabled(True)
         selectall = QtGui.QKeySequence(QtGui.QKeySequence.SelectAll)
         if selectall.matches("Ctrl+A") and sys.platform != 'darwin':
             # Only override the default if there is a collision.
             # Qt ctrl = cmd on OSX, so the match gets a false positive on OSX.
             selectall = "Ctrl+Shift+A"
         action.setShortcut(selectall)
         action.setShortcutContext(QtCore.Qt.WidgetWithChildrenShortcut)
         action.triggered.connect(self.select_all)
         self.addAction(action)
         self.select_all_action = action
 
         self.increase_font_size = QtGui.QAction("Bigger Font",
                 self,
                 shortcut=QtGui.QKeySequence.ZoomIn,
                 shortcutContext=QtCore.Qt.WidgetWithChildrenShortcut,
                 statusTip="Increase the font size by one point",
                 triggered=self._increase_font_size)
         self.addAction(self.increase_font_size)
 
         self.decrease_font_size = QtGui.QAction("Smaller Font",
                 self,
                 shortcut=QtGui.QKeySequence.ZoomOut,
                 shortcutContext=QtCore.Qt.WidgetWithChildrenShortcut,
                 statusTip="Decrease the font size by one point",
                 triggered=self._decrease_font_size)
         self.addAction(self.decrease_font_size)
 
         self.reset_font_size = QtGui.QAction("Normal Font",
                 self,
                 shortcut="Ctrl+0",
                 shortcutContext=QtCore.Qt.WidgetWithChildrenShortcut,
                 statusTip="Restore the Normal font size",
                 triggered=self.reset_font)
         self.addAction(self.reset_font_size)
 
         # Accept drag and drop events here. Drops were already turned off
         # in self._control when that widget was created.
         self.setAcceptDrops(True)
 
     #---------------------------------------------------------------------------
     # Drag and drop support
     #---------------------------------------------------------------------------
 
     def dragEnterEvent(self, e):
         if e.mimeData().hasUrls():
             # The link action should indicate to that the drop will insert
             # the file anme.
             e.setDropAction(QtCore.Qt.LinkAction)
             e.accept()
         elif e.mimeData().hasText():
             # By changing the action to copy we don't need to worry about
             # the user accidentally moving text around in the widget.
             e.setDropAction(QtCore.Qt.CopyAction)
             e.accept()
 
     def dragMoveEvent(self, e):
         if e.mimeData().hasUrls():
             pass
         elif e.mimeData().hasText():
             cursor = self._control.cursorForPosition(e.pos())
             if self._in_buffer(cursor.position()):
                 e.setDropAction(QtCore.Qt.CopyAction)
                 self._control.setTextCursor(cursor)
             else:
                 e.setDropAction(QtCore.Qt.IgnoreAction)
             e.accept()
 
     def dropEvent(self, e):
         if e.mimeData().hasUrls():
             self._keep_cursor_in_buffer()
             cursor = self._control.textCursor()
             filenames = [url.toLocalFile() for url in e.mimeData().urls()]
             text = ', '.join("'" + f.replace("'", "'\"'\"'") + "'"
                              for f in filenames)
             self._insert_plain_text_into_buffer(cursor, text)
         elif e.mimeData().hasText():
             cursor = self._control.cursorForPosition(e.pos())
             if self._in_buffer(cursor.position()):
                 text = e.mimeData().text()
                 self._insert_plain_text_into_buffer(cursor, text)
 
     def eventFilter(self, obj, event):
         """ Reimplemented to ensure a console-like behavior in the underlying
             text widgets.
         """
         etype = event.type()
         if etype == QtCore.QEvent.KeyPress:
 
             # Re-map keys for all filtered widgets.
             key = event.key()
             if self._control_key_down(event.modifiers()) and \
                     key in self._ctrl_down_remap:
                 new_event = QtGui.QKeyEvent(QtCore.QEvent.KeyPress,
                                             self._ctrl_down_remap[key],
                                             QtCore.Qt.NoModifier)
                 QtGui.qApp.sendEvent(obj, new_event)
                 return True
 
             elif obj == self._control:
                 return self._event_filter_console_keypress(event)
 
             elif obj == self._page_control:
                 return self._event_filter_page_keypress(event)
 
         # Make middle-click paste safe.
         elif etype == QtCore.QEvent.MouseButtonRelease and \
                 event.button() == QtCore.Qt.MidButton and \
                 obj == self._control.viewport():
             cursor = self._control.cursorForPosition(event.pos())
             self._control.setTextCursor(cursor)
             self.paste(QtGui.QClipboard.Selection)
             return True
 
         # Manually adjust the scrollbars *after* a resize event is dispatched.
         elif etype == QtCore.QEvent.Resize and not self._filter_resize:
             self._filter_resize = True
             QtGui.qApp.sendEvent(obj, event)
             self._adjust_scrollbars()
             self._filter_resize = False
             return True
 
         # Override shortcuts for all filtered widgets.
         elif etype == QtCore.QEvent.ShortcutOverride and \
                 self.override_shortcuts and \
                 self._control_key_down(event.modifiers()) and \
                 event.key() in self._shortcuts:
             event.accept()
 
         # Handle scrolling of the vsplit pager. This hack attempts to solve
         # problems with tearing of the help text inside the pager window.  This
         # happens only on Mac OS X with both PySide and PyQt. This fix isn't
         # perfect but makes the pager more usable.
         elif etype in self._pager_scroll_events and \
                 obj == self._page_control:
             self._page_control.repaint()
             return True
 
         elif etype == QtCore.QEvent.MouseMove:
             anchor = self._control.anchorAt(event.pos())
             QtGui.QToolTip.showText(event.globalPos(), anchor)
 
         return super(ConsoleWidget, self).eventFilter(obj, event)
 
     #---------------------------------------------------------------------------
     # 'QWidget' interface
     #---------------------------------------------------------------------------
 
     def sizeHint(self):
         """ Reimplemented to suggest a size that is 80 characters wide and
             25 lines high.
         """
         font_metrics = QtGui.QFontMetrics(self.font)
         margin = (self._control.frameWidth() +
                   self._control.document().documentMargin()) * 2
         style = self.style()
         splitwidth = style.pixelMetric(QtGui.QStyle.PM_SplitterWidth)
 
         # Note 1: Despite my best efforts to take the various margins into
         # account, the width is still coming out a bit too small, so we include
         # a fudge factor of one character here.
         # Note 2: QFontMetrics.maxWidth is not used here or anywhere else due
         # to a Qt bug on certain Mac OS systems where it returns 0.
         width = font_metrics.width(' ') * self.width + margin
         width += style.pixelMetric(QtGui.QStyle.PM_ScrollBarExtent)
         if self.paging == 'hsplit':
             width = width * 2 + splitwidth
 
         height = font_metrics.height() * self.height + margin
         if self.paging == 'vsplit':
             height = height * 2 + splitwidth
 
         return QtCore.QSize(width, height)
 
     #---------------------------------------------------------------------------
     # 'ConsoleWidget' public interface
     #---------------------------------------------------------------------------
 
     def can_copy(self):
         """ Returns whether text can be copied to the clipboard.
         """
         return self._control.textCursor().hasSelection()
 
     def can_cut(self):
         """ Returns whether text can be cut to the clipboard.
         """
         cursor = self._control.textCursor()
         return (cursor.hasSelection() and
                 self._in_buffer(cursor.anchor()) and
                 self._in_buffer(cursor.position()))
 
     def can_paste(self):
         """ Returns whether text can be pasted from the clipboard.
         """
         if self._control.textInteractionFlags() & QtCore.Qt.TextEditable:
             return bool(QtGui.QApplication.clipboard().text())
         return False
 
     def clear(self, keep_input=True):
         """ Clear the console.
 
         Parameters:
         -----------
         keep_input : bool, optional (default True)
             If set, restores the old input buffer if a new prompt is written.
         """
         if self._executing:
             self._control.clear()
         else:
             if keep_input:
                 input_buffer = self.input_buffer
             self._control.clear()
             self._show_prompt()
             if keep_input:
                 self.input_buffer = input_buffer
 
     def copy(self):
         """ Copy the currently selected text to the clipboard.
         """
         self.layout().currentWidget().copy()
 
     def copy_anchor(self, anchor):
         """ Copy anchor text to the clipboard
         """
         QtGui.QApplication.clipboard().setText(anchor)
 
     def cut(self):
         """ Copy the currently selected text to the clipboard and delete it
             if it's inside the input buffer.
         """
         self.copy()
         if self.can_cut():
             self._control.textCursor().removeSelectedText()
 
     def execute(self, source=None, hidden=False, interactive=False):
         """ Executes source or the input buffer, possibly prompting for more
         input.
 
         Parameters:
         -----------
         source : str, optional
 
             The source to execute. If not specified, the input buffer will be
             used. If specified and 'hidden' is False, the input buffer will be
             replaced with the source before execution.
 
         hidden : bool, optional (default False)
 
             If set, no output will be shown and the prompt will not be modified.
             In other words, it will be completely invisible to the user that
             an execution has occurred.
 
         interactive : bool, optional (default False)
 
             Whether the console is to treat the source as having been manually
             entered by the user. The effect of this parameter depends on the
             subclass implementation.
 
         Raises:
         -------
         RuntimeError
             If incomplete input is given and 'hidden' is True. In this case,
             it is not possible to prompt for more input.
 
         Returns:
         --------
         A boolean indicating whether the source was executed.
         """
         # WARNING: The order in which things happen here is very particular, in
         # large part because our syntax highlighting is fragile. If you change
         # something, test carefully!
 
         # Decide what to execute.
         if source is None:
             source = self.input_buffer
             if not hidden:
                 # A newline is appended later, but it should be considered part
                 # of the input buffer.
                 source += '\n'
         elif not hidden:
             self.input_buffer = source
 
         # Execute the source or show a continuation prompt if it is incomplete.
         if self.execute_on_complete_input:
             complete = self._is_complete(source, interactive)
         else:
             complete = not interactive
         if hidden:
             if complete or not self.execute_on_complete_input:
                 self._execute(source, hidden)
             else:
                 error = 'Incomplete noninteractive input: "%s"'
                 raise RuntimeError(error % source)
         else:
             if complete:
                 self._append_plain_text('\n')
                 self._input_buffer_executing = self.input_buffer
                 self._executing = True
                 self._prompt_finished()
 
                 # The maximum block count is only in effect during execution.
                 # This ensures that _prompt_pos does not become invalid due to
                 # text truncation.
                 self._control.document().setMaximumBlockCount(self.buffer_size)
 
                 # Setting a positive maximum block count will automatically
                 # disable the undo/redo history, but just to be safe:
                 self._control.setUndoRedoEnabled(False)
 
                 # Perform actual execution.
                 self._execute(source, hidden)
 
             else:
                 # Do this inside an edit block so continuation prompts are
                 # removed seamlessly via undo/redo.
                 cursor = self._get_end_cursor()
                 cursor.beginEditBlock()
                 cursor.insertText('\n')
                 self._insert_continuation_prompt(cursor)
                 cursor.endEditBlock()
 
                 # Do not do this inside the edit block. It works as expected
                 # when using a QPlainTextEdit control, but does not have an
                 # effect when using a QTextEdit. I believe this is a Qt bug.
                 self._control.moveCursor(QtGui.QTextCursor.End)
 
         return complete
 
     def export_html(self):
         """ Shows a dialog to export HTML/XML in various formats.
         """
         self._html_exporter.export()
 
     def _get_input_buffer(self, force=False):
         """ The text that the user has entered entered at the current prompt.
 
         If the console is currently executing, the text that is executing will
         always be returned.
         """
         # If we're executing, the input buffer may not even exist anymore due to
         # the limit imposed by 'buffer_size'. Therefore, we store it.
         if self._executing and not force:
             return self._input_buffer_executing
 
         cursor = self._get_end_cursor()
         cursor.setPosition(self._prompt_pos, QtGui.QTextCursor.KeepAnchor)
         input_buffer = cursor.selection().toPlainText()
 
         # Strip out continuation prompts.
         return input_buffer.replace('\n' + self._continuation_prompt, '\n')
 
     def _set_input_buffer(self, string):
         """ Sets the text in the input buffer.
 
         If the console is currently executing, this call has no *immediate*
         effect. When the execution is finished, the input buffer will be updated
         appropriately.
         """
         # If we're executing, store the text for later.
         if self._executing:
             self._input_buffer_pending = string
             return
 
         # Remove old text.
         cursor = self._get_end_cursor()
         cursor.beginEditBlock()
         cursor.setPosition(self._prompt_pos, QtGui.QTextCursor.KeepAnchor)
         cursor.removeSelectedText()
 
         # Insert new text with continuation prompts.
         self._insert_plain_text_into_buffer(self._get_prompt_cursor(), string)
         cursor.endEditBlock()
         self._control.moveCursor(QtGui.QTextCursor.End)
 
     input_buffer = property(_get_input_buffer, _set_input_buffer)
 
     def _get_font(self):
         """ The base font being used by the ConsoleWidget.
         """
         return self._control.document().defaultFont()
 
     def _set_font(self, font):
         """ Sets the base font for the ConsoleWidget to the specified QFont.
         """
         font_metrics = QtGui.QFontMetrics(font)
         self._control.setTabStopWidth(self.tab_width * font_metrics.width(' '))
 
         self._completion_widget.setFont(font)
         self._control.document().setDefaultFont(font)
         if self._page_control:
             self._page_control.document().setDefaultFont(font)
 
         self.font_changed.emit(font)
 
     font = property(_get_font, _set_font)
 
     def open_anchor(self, anchor):
         """ Open selected anchor in the default webbrowser
         """
         webbrowser.open( anchor )
 
     def paste(self, mode=QtGui.QClipboard.Clipboard):
         """ Paste the contents of the clipboard into the input region.
 
         Parameters:
         -----------
         mode : QClipboard::Mode, optional [default QClipboard::Clipboard]
 
             Controls which part of the system clipboard is used. This can be
             used to access the selection clipboard in X11 and the Find buffer
             in Mac OS. By default, the regular clipboard is used.
         """
         if self._control.textInteractionFlags() & QtCore.Qt.TextEditable:
             # Make sure the paste is safe.
             self._keep_cursor_in_buffer()
             cursor = self._control.textCursor()
 
             # Remove any trailing newline, which confuses the GUI and forces the
             # user to backspace.
             text = QtGui.QApplication.clipboard().text(mode).rstrip()
             self._insert_plain_text_into_buffer(cursor, dedent(text))
 
     def print_(self, printer = None):
         """ Print the contents of the ConsoleWidget to the specified QPrinter.
         """
         if (not printer):
             printer = QtGui.QPrinter()
             if(QtGui.QPrintDialog(printer).exec_() != QtGui.QDialog.Accepted):
                 return
         self._control.print_(printer)
 
     def prompt_to_top(self):
         """ Moves the prompt to the top of the viewport.
         """
         if not self._executing:
             prompt_cursor = self._get_prompt_cursor()
             if self._get_cursor().blockNumber() < prompt_cursor.blockNumber():
                 self._set_cursor(prompt_cursor)
             self._set_top_cursor(prompt_cursor)
 
     def redo(self):
         """ Redo the last operation. If there is no operation to redo, nothing
             happens.
         """
         self._control.redo()
 
     def reset_font(self):
         """ Sets the font to the default fixed-width font for this platform.
         """
         if sys.platform == 'win32':
             # Consolas ships with Vista/Win7, fallback to Courier if needed
             fallback = 'Courier'
         elif sys.platform == 'darwin':
             # OSX always has Monaco
             fallback = 'Monaco'
         else:
             # Monospace should always exist
             fallback = 'Monospace'
         font = get_font(self.font_family, fallback)
         if self.font_size:
             font.setPointSize(self.font_size)
         else:
             font.setPointSize(QtGui.qApp.font().pointSize())
         font.setStyleHint(QtGui.QFont.TypeWriter)
         self._set_font(font)
 
     def change_font_size(self, delta):
         """Change the font size by the specified amount (in points).
         """
         font = self.font
         size = max(font.pointSize() + delta, 1) # minimum 1 point
         font.setPointSize(size)
         self._set_font(font)
 
     def _increase_font_size(self):
         self.change_font_size(1)
 
     def _decrease_font_size(self):
         self.change_font_size(-1)
 
     def select_all(self):
         """ Selects all the text in the buffer.
         """
         self._control.selectAll()
 
     def _get_tab_width(self):
         """ The width (in terms of space characters) for tab characters.
         """
         return self._tab_width
 
     def _set_tab_width(self, tab_width):
         """ Sets the width (in terms of space characters) for tab characters.
         """
         font_metrics = QtGui.QFontMetrics(self.font)
         self._control.setTabStopWidth(tab_width * font_metrics.width(' '))
 
         self._tab_width = tab_width
 
     tab_width = property(_get_tab_width, _set_tab_width)
 
     def undo(self):
         """ Undo the last operation. If there is no operation to undo, nothing
             happens.
         """
         self._control.undo()
 
     #---------------------------------------------------------------------------
     # 'ConsoleWidget' abstract interface
     #---------------------------------------------------------------------------
 
     def _is_complete(self, source, interactive):
         """ Returns whether 'source' can be executed. When triggered by an
             Enter/Return key press, 'interactive' is True; otherwise, it is
             False.
         """
         raise NotImplementedError
 
     def _execute(self, source, hidden):
         """ Execute 'source'. If 'hidden', do not show any output.
         """
         raise NotImplementedError
 
     def _prompt_started_hook(self):
         """ Called immediately after a new prompt is displayed.
         """
         pass
 
     def _prompt_finished_hook(self):
         """ Called immediately after a prompt is finished, i.e. when some input
             will be processed and a new prompt displayed.
         """
         pass
 
     def _up_pressed(self, shift_modifier):
         """ Called when the up key is pressed. Returns whether to continue
             processing the event.
         """
         return True
 
     def _down_pressed(self, shift_modifier):
         """ Called when the down key is pressed. Returns whether to continue
             processing the event.
         """
         return True
 
     def _tab_pressed(self):
         """ Called when the tab key is pressed. Returns whether to continue
             processing the event.
         """
         return False
 
     #--------------------------------------------------------------------------
     # 'ConsoleWidget' protected interface
     #--------------------------------------------------------------------------
 
     def _append_custom(self, insert, input, before_prompt=False, *args, **kwargs):
         """ A low-level method for appending content to the end of the buffer.
 
         If 'before_prompt' is enabled, the content will be inserted before the
         current prompt, if there is one.
         """
         # Determine where to insert the content.
         cursor = self._control.textCursor()
         if before_prompt and (self._reading or not self._executing):
             self._flush_pending_stream()
             cursor.setPosition(self._append_before_prompt_pos)
         else:
             if insert != self._insert_plain_text:
                 self._flush_pending_stream()
             cursor.movePosition(QtGui.QTextCursor.End)
         start_pos = cursor.position()
 
         # Perform the insertion.
         result = insert(cursor, input, *args, **kwargs)
 
         # Adjust the prompt position if we have inserted before it. This is safe
         # because buffer truncation is disabled when not executing.
         if before_prompt and not self._executing:
             diff = cursor.position() - start_pos
             self._append_before_prompt_pos += diff
             self._prompt_pos += diff
 
         return result
 
     def _append_block(self, block_format=None, before_prompt=False):
         """ Appends an new QTextBlock to the end of the console buffer.
         """
         self._append_custom(self._insert_block, block_format, before_prompt)
 
     def _append_html(self, html, before_prompt=False):
         """ Appends HTML at the end of the console buffer.
         """
         self._append_custom(self._insert_html, html, before_prompt)
 
     def _append_html_fetching_plain_text(self, html, before_prompt=False):
         """ Appends HTML, then returns the plain text version of it.
         """
         return self._append_custom(self._insert_html_fetching_plain_text,
                                    html, before_prompt)
 
     def _append_plain_text(self, text, before_prompt=False):
         """ Appends plain text, processing ANSI codes if enabled.
         """
         self._append_custom(self._insert_plain_text, text, before_prompt)
 
     def _cancel_completion(self):
         """ If text completion is progress, cancel it.
         """
         self._completion_widget.cancel_completion()
 
     def _clear_temporary_buffer(self):
         """ Clears the "temporary text" buffer, i.e. all the text following
             the prompt region.
         """
         # Select and remove all text below the input buffer.
         cursor = self._get_prompt_cursor()
         prompt = self._continuation_prompt.lstrip()
         if(self._temp_buffer_filled):
             self._temp_buffer_filled = False
             while cursor.movePosition(QtGui.QTextCursor.NextBlock):
                 temp_cursor = QtGui.QTextCursor(cursor)
                 temp_cursor.select(QtGui.QTextCursor.BlockUnderCursor)
                 text = temp_cursor.selection().toPlainText().lstrip()
                 if not text.startswith(prompt):
                     break
         else:
             # We've reached the end of the input buffer and no text follows.
             return
         cursor.movePosition(QtGui.QTextCursor.Left) # Grab the newline.
         cursor.movePosition(QtGui.QTextCursor.End,
                             QtGui.QTextCursor.KeepAnchor)
         cursor.removeSelectedText()
 
         # After doing this, we have no choice but to clear the undo/redo
         # history. Otherwise, the text is not "temporary" at all, because it
         # can be recalled with undo/redo. Unfortunately, Qt does not expose
         # fine-grained control to the undo/redo system.
         if self._control.isUndoRedoEnabled():
             self._control.setUndoRedoEnabled(False)
             self._control.setUndoRedoEnabled(True)
 
     def _complete_with_items(self, cursor, items):
         """ Performs completion with 'items' at the specified cursor location.
         """
         self._cancel_completion()
 
         if len(items) == 1:
             cursor.setPosition(self._control.textCursor().position(),
                                QtGui.QTextCursor.KeepAnchor)
             cursor.insertText(items[0])
 
         elif len(items) > 1:
             current_pos = self._control.textCursor().position()
             prefix = commonprefix(items)
             if prefix:
                 cursor.setPosition(current_pos, QtGui.QTextCursor.KeepAnchor)
                 cursor.insertText(prefix)
                 current_pos = cursor.position()
 
             cursor.movePosition(QtGui.QTextCursor.Left, n=len(prefix))
             self._completion_widget.show_items(cursor, items)
 
 
     def _fill_temporary_buffer(self, cursor, text, html=False):
         """fill the area below the active editting zone with text"""
 
         current_pos = self._control.textCursor().position()
 
         cursor.beginEditBlock()
         self._append_plain_text('\n')
         self._page(text, html=html)
         cursor.endEditBlock()
 
         cursor.setPosition(current_pos)
         self._control.moveCursor(QtGui.QTextCursor.End)
         self._control.setTextCursor(cursor)
 
         self._temp_buffer_filled = True
 
 
     def _context_menu_make(self, pos):
         """ Creates a context menu for the given QPoint (in widget coordinates).
         """
         menu = QtGui.QMenu(self)
 
         self.cut_action = menu.addAction('Cut', self.cut)
         self.cut_action.setEnabled(self.can_cut())
         self.cut_action.setShortcut(QtGui.QKeySequence.Cut)
 
         self.copy_action = menu.addAction('Copy', self.copy)
         self.copy_action.setEnabled(self.can_copy())
         self.copy_action.setShortcut(QtGui.QKeySequence.Copy)
 
         self.paste_action = menu.addAction('Paste', self.paste)
         self.paste_action.setEnabled(self.can_paste())
         self.paste_action.setShortcut(QtGui.QKeySequence.Paste)
 
         anchor = self._control.anchorAt(pos)
         if anchor:
             menu.addSeparator()
             self.copy_link_action = menu.addAction(
                 'Copy Link Address', lambda: self.copy_anchor(anchor=anchor))
             self.open_link_action = menu.addAction(
                 'Open Link', lambda: self.open_anchor(anchor=anchor))
 
         menu.addSeparator()
         menu.addAction(self.select_all_action)
 
         menu.addSeparator()
         menu.addAction(self.export_action)
         menu.addAction(self.print_action)
 
         return menu
 
     def _control_key_down(self, modifiers, include_command=False):
         """ Given a KeyboardModifiers flags object, return whether the Control
         key is down.
 
         Parameters:
         -----------
         include_command : bool, optional (default True)
             Whether to treat the Command key as a (mutually exclusive) synonym
             for Control when in Mac OS.
         """
         # Note that on Mac OS, ControlModifier corresponds to the Command key
         # while MetaModifier corresponds to the Control key.
         if sys.platform == 'darwin':
             down = include_command and (modifiers & QtCore.Qt.ControlModifier)
             return bool(down) ^ bool(modifiers & QtCore.Qt.MetaModifier)
         else:
             return bool(modifiers & QtCore.Qt.ControlModifier)
 
     def _create_control(self):
         """ Creates and connects the underlying text widget.
         """
         # Create the underlying control.
         if self.custom_control:
             control = self.custom_control()
         elif self.kind == 'plain':
             control = QtGui.QPlainTextEdit()
         elif self.kind == 'rich':
             control = QtGui.QTextEdit()
             control.setAcceptRichText(False)
             control.setMouseTracking(True)
 
         # Prevent the widget from handling drops, as we already provide
         # the logic in this class.
         control.setAcceptDrops(False)
 
         # Install event filters. The filter on the viewport is needed for
         # mouse events.
         control.installEventFilter(self)
         control.viewport().installEventFilter(self)
 
         # Connect signals.
         control.customContextMenuRequested.connect(
             self._custom_context_menu_requested)
         control.copyAvailable.connect(self.copy_available)
         control.redoAvailable.connect(self.redo_available)
         control.undoAvailable.connect(self.undo_available)
 
         # Hijack the document size change signal to prevent Qt from adjusting
         # the viewport's scrollbar. We are relying on an implementation detail
         # of Q(Plain)TextEdit here, which is potentially dangerous, but without
         # this functionality we cannot create a nice terminal interface.
         layout = control.document().documentLayout()
         layout.documentSizeChanged.disconnect()
         layout.documentSizeChanged.connect(self._adjust_scrollbars)
 
         # Configure the control.
         control.setAttribute(QtCore.Qt.WA_InputMethodEnabled, True)
         control.setContextMenuPolicy(QtCore.Qt.CustomContextMenu)
         control.setReadOnly(True)
         control.setUndoRedoEnabled(False)
         control.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)
         return control
 
     def _create_page_control(self):
         """ Creates and connects the underlying paging widget.
         """
         if self.custom_page_control:
             control = self.custom_page_control()
         elif self.kind == 'plain':
             control = QtGui.QPlainTextEdit()
         elif self.kind == 'rich':
             control = QtGui.QTextEdit()
         control.installEventFilter(self)
         viewport = control.viewport()
         viewport.installEventFilter(self)
         control.setReadOnly(True)
         control.setUndoRedoEnabled(False)
         control.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)
         return control
 
     def _event_filter_console_keypress(self, event):
         """ Filter key events for the underlying text widget to create a
             console-like interface.
         """
         intercepted = False
         cursor = self._control.textCursor()
         position = cursor.position()
         key = event.key()
         ctrl_down = self._control_key_down(event.modifiers())
         alt_down = event.modifiers() & QtCore.Qt.AltModifier
         shift_down = event.modifiers() & QtCore.Qt.ShiftModifier
 
         #------ Special sequences ----------------------------------------------
 
         if event.matches(QtGui.QKeySequence.Copy):
             self.copy()
             intercepted = True
 
         elif event.matches(QtGui.QKeySequence.Cut):
             self.cut()
             intercepted = True
 
         elif event.matches(QtGui.QKeySequence.Paste):
             self.paste()
             intercepted = True
 
         #------ Special modifier logic -----------------------------------------
 
         elif key in (QtCore.Qt.Key_Return, QtCore.Qt.Key_Enter):
             intercepted = True
 
             # Special handling when tab completing in text mode.
             self._cancel_completion()
 
             if self._in_buffer(position):
                 # Special handling when a reading a line of raw input.
                 if self._reading:
                     self._append_plain_text('\n')
                     self._reading = False
                     if self._reading_callback:
                         self._reading_callback()
 
                 # If the input buffer is a single line or there is only
                 # whitespace after the cursor, execute. Otherwise, split the
                 # line with a continuation prompt.
                 elif not self._executing:
                     cursor.movePosition(QtGui.QTextCursor.End,
                                         QtGui.QTextCursor.KeepAnchor)
                     at_end = len(cursor.selectedText().strip()) == 0
                     single_line = (self._get_end_cursor().blockNumber() ==
                                    self._get_prompt_cursor().blockNumber())
                     if (at_end or shift_down or single_line) and not ctrl_down:
                         self.execute(interactive = not shift_down)
                     else:
                         # Do this inside an edit block for clean undo/redo.
                         cursor.beginEditBlock()
                         cursor.setPosition(position)
                         cursor.insertText('\n')
                         self._insert_continuation_prompt(cursor)
                         cursor.endEditBlock()
 
                         # Ensure that the whole input buffer is visible.
                         # FIXME: This will not be usable if the input buffer is
                         # taller than the console widget.
                         self._control.moveCursor(QtGui.QTextCursor.End)
                         self._control.setTextCursor(cursor)
 
         #------ Control/Cmd modifier -------------------------------------------
 
         elif ctrl_down:
             if key == QtCore.Qt.Key_G:
                 self._keyboard_quit()
                 intercepted = True
 
             elif key == QtCore.Qt.Key_K:
                 if self._in_buffer(position):
                     cursor.clearSelection()
                     cursor.movePosition(QtGui.QTextCursor.EndOfLine,
                                         QtGui.QTextCursor.KeepAnchor)
                     if not cursor.hasSelection():
                         # Line deletion (remove continuation prompt)
                         cursor.movePosition(QtGui.QTextCursor.NextBlock,
                                             QtGui.QTextCursor.KeepAnchor)
                         cursor.movePosition(QtGui.QTextCursor.Right,
                                             QtGui.QTextCursor.KeepAnchor,
                                             len(self._continuation_prompt))
                     self._kill_ring.kill_cursor(cursor)
                     self._set_cursor(cursor)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_L:
                 self.prompt_to_top()
                 intercepted = True
 
             elif key == QtCore.Qt.Key_O:
                 if self._page_control and self._page_control.isVisible():
                     self._page_control.setFocus()
                 intercepted = True
 
             elif key == QtCore.Qt.Key_U:
                 if self._in_buffer(position):
                     cursor.clearSelection()
                     start_line = cursor.blockNumber()
                     if start_line == self._get_prompt_cursor().blockNumber():
                         offset = len(self._prompt)
                     else:
                         offset = len(self._continuation_prompt)
                     cursor.movePosition(QtGui.QTextCursor.StartOfBlock,
                                         QtGui.QTextCursor.KeepAnchor)
                     cursor.movePosition(QtGui.QTextCursor.Right,
                                         QtGui.QTextCursor.KeepAnchor, offset)
                     self._kill_ring.kill_cursor(cursor)
                     self._set_cursor(cursor)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Y:
                 self._keep_cursor_in_buffer()
                 self._kill_ring.yank()
                 intercepted = True
 
             elif key in (QtCore.Qt.Key_Backspace, QtCore.Qt.Key_Delete):
                 if key == QtCore.Qt.Key_Backspace:
                     cursor = self._get_word_start_cursor(position)
                 else: # key == QtCore.Qt.Key_Delete
                     cursor = self._get_word_end_cursor(position)
                 cursor.setPosition(position, QtGui.QTextCursor.KeepAnchor)
                 self._kill_ring.kill_cursor(cursor)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_D:
                 if len(self.input_buffer) == 0:
                     self.exit_requested.emit(self)
                 else:
                     new_event = QtGui.QKeyEvent(QtCore.QEvent.KeyPress,
                                                 QtCore.Qt.Key_Delete,
                                                 QtCore.Qt.NoModifier)
                     QtGui.qApp.sendEvent(self._control, new_event)
                     intercepted = True
 
         #------ Alt modifier ---------------------------------------------------
 
         elif alt_down:
             if key == QtCore.Qt.Key_B:
                 self._set_cursor(self._get_word_start_cursor(position))
                 intercepted = True
 
             elif key == QtCore.Qt.Key_F:
                 self._set_cursor(self._get_word_end_cursor(position))
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Y:
                 self._kill_ring.rotate()
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Backspace:
                 cursor = self._get_word_start_cursor(position)
                 cursor.setPosition(position, QtGui.QTextCursor.KeepAnchor)
                 self._kill_ring.kill_cursor(cursor)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_D:
                 cursor = self._get_word_end_cursor(position)
                 cursor.setPosition(position, QtGui.QTextCursor.KeepAnchor)
                 self._kill_ring.kill_cursor(cursor)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Delete:
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Greater:
                 self._control.moveCursor(QtGui.QTextCursor.End)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Less:
                 self._control.setTextCursor(self._get_prompt_cursor())
                 intercepted = True
 
         #------ No modifiers ---------------------------------------------------
 
         else:
             if shift_down:
                 anchormode = QtGui.QTextCursor.KeepAnchor
             else:
                 anchormode = QtGui.QTextCursor.MoveAnchor
 
             if key == QtCore.Qt.Key_Escape:
                 self._keyboard_quit()
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Up:
                 if self._reading or not self._up_pressed(shift_down):
                     intercepted = True
                 else:
                     prompt_line = self._get_prompt_cursor().blockNumber()
                     intercepted = cursor.blockNumber() <= prompt_line
 
             elif key == QtCore.Qt.Key_Down:
                 if self._reading or not self._down_pressed(shift_down):
                     intercepted = True
                 else:
                     end_line = self._get_end_cursor().blockNumber()
                     intercepted = cursor.blockNumber() == end_line
 
             elif key == QtCore.Qt.Key_Tab:
                 if not self._reading:
                     if self._tab_pressed():
                         # real tab-key, insert four spaces
                         cursor.insertText(' '*4)
                     intercepted = True
 
             elif key == QtCore.Qt.Key_Left:
 
                 # Move to the previous line
                 line, col = cursor.blockNumber(), cursor.columnNumber()
                 if line > self._get_prompt_cursor().blockNumber() and \
                         col == len(self._continuation_prompt):
                     self._control.moveCursor(QtGui.QTextCursor.PreviousBlock,
                                              mode=anchormode)
                     self._control.moveCursor(QtGui.QTextCursor.EndOfBlock,
                                              mode=anchormode)
                     intercepted = True
 
                 # Regular left movement
                 else:
                     intercepted = not self._in_buffer(position - 1)
 
             elif key == QtCore.Qt.Key_Right:
                 original_block_number = cursor.blockNumber()
                 cursor.movePosition(QtGui.QTextCursor.Right,
                                 mode=anchormode)
                 if cursor.blockNumber() != original_block_number:
                     cursor.movePosition(QtGui.QTextCursor.Right,
                                         n=len(self._continuation_prompt),
                                         mode=anchormode)
                 self._set_cursor(cursor)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Home:
                 start_line = cursor.blockNumber()
                 if start_line == self._get_prompt_cursor().blockNumber():
                     start_pos = self._prompt_pos
                 else:
                     cursor.movePosition(QtGui.QTextCursor.StartOfBlock,
                                         QtGui.QTextCursor.KeepAnchor)
                     start_pos = cursor.position()
                     start_pos += len(self._continuation_prompt)
                     cursor.setPosition(position)
                 if shift_down and self._in_buffer(position):
                     cursor.setPosition(start_pos, QtGui.QTextCursor.KeepAnchor)
                 else:
                     cursor.setPosition(start_pos)
                 self._set_cursor(cursor)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Backspace:
 
                 # Line deletion (remove continuation prompt)
                 line, col = cursor.blockNumber(), cursor.columnNumber()
                 if not self._reading and \
                         col == len(self._continuation_prompt) and \
                         line > self._get_prompt_cursor().blockNumber():
                     cursor.beginEditBlock()
                     cursor.movePosition(QtGui.QTextCursor.StartOfBlock,
                                         QtGui.QTextCursor.KeepAnchor)
                     cursor.removeSelectedText()
                     cursor.deletePreviousChar()
                     cursor.endEditBlock()
                     intercepted = True
 
                 # Regular backwards deletion
                 else:
                     anchor = cursor.anchor()
                     if anchor == position:
                         intercepted = not self._in_buffer(position - 1)
                     else:
                         intercepted = not self._in_buffer(min(anchor, position))
 
             elif key == QtCore.Qt.Key_Delete:
 
                 # Line deletion (remove continuation prompt)
                 if not self._reading and self._in_buffer(position) and \
                         cursor.atBlockEnd() and not cursor.hasSelection():
                     cursor.movePosition(QtGui.QTextCursor.NextBlock,
                                         QtGui.QTextCursor.KeepAnchor)
                     cursor.movePosition(QtGui.QTextCursor.Right,
                                         QtGui.QTextCursor.KeepAnchor,
                                         len(self._continuation_prompt))
                     cursor.removeSelectedText()
                     intercepted = True
 
                 # Regular forwards deletion:
                 else:
                     anchor = cursor.anchor()
                     intercepted = (not self._in_buffer(anchor) or
                                    not self._in_buffer(position))
 
         # Don't move the cursor if Control/Cmd is pressed to allow copy-paste
         # using the keyboard in any part of the buffer. Also, permit scrolling
         # with Page Up/Down keys. Finally, if we're executing, don't move the
         # cursor (if even this made sense, we can't guarantee that the prompt
         # position is still valid due to text truncation).
         if not (self._control_key_down(event.modifiers(), include_command=True)
                 or key in (QtCore.Qt.Key_PageUp, QtCore.Qt.Key_PageDown)
                 or (self._executing and not self._reading)):
             self._keep_cursor_in_buffer()
 
         return intercepted
 
     def _event_filter_page_keypress(self, event):
         """ Filter key events for the paging widget to create console-like
             interface.
         """
         key = event.key()
         ctrl_down = self._control_key_down(event.modifiers())
         alt_down = event.modifiers() & QtCore.Qt.AltModifier
 
         if ctrl_down:
             if key == QtCore.Qt.Key_O:
                 self._control.setFocus()
                 intercept = True
 
         elif alt_down:
             if key == QtCore.Qt.Key_Greater:
                 self._page_control.moveCursor(QtGui.QTextCursor.End)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Less:
                 self._page_control.moveCursor(QtGui.QTextCursor.Start)
                 intercepted = True
 
         elif key in (QtCore.Qt.Key_Q, QtCore.Qt.Key_Escape):
             if self._splitter:
                 self._page_control.hide()
                 self._control.setFocus()
             else:
                 self.layout().setCurrentWidget(self._control)
             return True
 
         elif key in (QtCore.Qt.Key_Enter, QtCore.Qt.Key_Return,
                      QtCore.Qt.Key_Tab):
             new_event = QtGui.QKeyEvent(QtCore.QEvent.KeyPress,
                                         QtCore.Qt.Key_PageDown,
                                         QtCore.Qt.NoModifier)
             QtGui.qApp.sendEvent(self._page_control, new_event)
             return True
 
         elif key == QtCore.Qt.Key_Backspace:
             new_event = QtGui.QKeyEvent(QtCore.QEvent.KeyPress,
                                         QtCore.Qt.Key_PageUp,
                                         QtCore.Qt.NoModifier)
             QtGui.qApp.sendEvent(self._page_control, new_event)
             return True
 
         return False
 
     def _flush_pending_stream(self):
         """ Flush out pending text into the widget. """
         text = self._pending_insert_text
         self._pending_insert_text = []
         buffer_size = self._control.document().maximumBlockCount()
         if buffer_size > 0:
             text = self._get_last_lines_from_list(text, buffer_size)
         text = ''.join(text)
         t = time.time()
         self._insert_plain_text(self._get_end_cursor(), text, flush=True)
         # Set the flush interval to equal the maximum time to update text.
         self._pending_text_flush_interval.setInterval(max(100,
                                                  (time.time()-t)*1000))
 
     def _format_as_columns(self, items, separator='  '):
         """ Transform a list of strings into a single string with columns.
 
         Parameters
         ----------
         items : sequence of strings
             The strings to process.
 
         separator : str, optional [default is two spaces]
             The string that separates columns.
 
         Returns
         -------
         The formatted string.
         """
         # Calculate the number of characters available.
         width = self._control.viewport().width()
         char_width = QtGui.QFontMetrics(self.font).width(' ')
         displaywidth = max(10, (width / char_width) - 1)
 
         return columnize(items, separator, displaywidth)
 
     def _get_block_plain_text(self, block):
         """ Given a QTextBlock, return its unformatted text.
         """
         cursor = QtGui.QTextCursor(block)
         cursor.movePosition(QtGui.QTextCursor.StartOfBlock)
         cursor.movePosition(QtGui.QTextCursor.EndOfBlock,
                             QtGui.QTextCursor.KeepAnchor)
         return cursor.selection().toPlainText()
 
     def _get_cursor(self):
         """ Convenience method that returns a cursor for the current position.
         """
         return self._control.textCursor()
 
     def _get_end_cursor(self):
         """ Convenience method that returns a cursor for the last character.
         """
         cursor = self._control.textCursor()
         cursor.movePosition(QtGui.QTextCursor.End)
         return cursor
 
     def _get_input_buffer_cursor_column(self):
         """ Returns the column of the cursor in the input buffer, excluding the
             contribution by the prompt, or -1 if there is no such column.
         """
         prompt = self._get_input_buffer_cursor_prompt()
         if prompt is None:
             return -1
         else:
             cursor = self._control.textCursor()
             return cursor.columnNumber() - len(prompt)
 
     def _get_input_buffer_cursor_line(self):
         """ Returns the text of the line of the input buffer that contains the
             cursor, or None if there is no such line.
         """
         prompt = self._get_input_buffer_cursor_prompt()
         if prompt is None:
             return None
         else:
             cursor = self._control.textCursor()
             text = self._get_block_plain_text(cursor.block())
             return text[len(prompt):]
 
     def _get_input_buffer_cursor_prompt(self):
         """ Returns the (plain text) prompt for line of the input buffer that
             contains the cursor, or None if there is no such line.
         """
         if self._executing:
             return None
         cursor = self._control.textCursor()
         if cursor.position() >= self._prompt_pos:
             if cursor.blockNumber() == self._get_prompt_cursor().blockNumber():
                 return self._prompt
             else:
                 return self._continuation_prompt
         else:
             return None
 
     def _get_last_lines(self, text, num_lines, return_count=False):
         """ Return last specified number of lines of text (like `tail -n`).
         If return_count is True, returns a tuple of clipped text and the
         number of lines in the clipped text.
         """
         pos = len(text)
         if pos < num_lines:
             if return_count:
                 return text, text.count('\n') if return_count else text
             else:
                 return text
         i = 0
         while i < num_lines:
             pos = text.rfind('\n', None, pos)
             if pos == -1:
                 pos = None
                 break
             i += 1
         if return_count:
             return text[pos:], i
         else:
             return text[pos:]
 
     def _get_last_lines_from_list(self, text_list, num_lines):
         """ Return the list of text clipped to last specified lines.
         """
         ret = []
         lines_pending = num_lines
         for text in reversed(text_list):
             text, lines_added = self._get_last_lines(text, lines_pending,
                                                      return_count=True)
             ret.append(text)
             lines_pending -= lines_added
             if lines_pending <= 0:
                 break
         return ret[::-1]
 
     def _get_prompt_cursor(self):
         """ Convenience method that returns a cursor for the prompt position.
         """
         cursor = self._control.textCursor()
         cursor.setPosition(self._prompt_pos)
         return cursor
 
     def _get_selection_cursor(self, start, end):
         """ Convenience method that returns a cursor with text selected between
             the positions 'start' and 'end'.
         """
         cursor = self._control.textCursor()
         cursor.setPosition(start)
         cursor.setPosition(end, QtGui.QTextCursor.KeepAnchor)
         return cursor
 
     def _get_word_start_cursor(self, position):
         """ Find the start of the word to the left the given position. If a
             sequence of non-word characters precedes the first word, skip over
             them. (This emulates the behavior of bash, emacs, etc.)
         """
         document = self._control.document()
         position -= 1
         while position >= self._prompt_pos and \
                   not is_letter_or_number(document.characterAt(position)):
             position -= 1
         while position >= self._prompt_pos and \
                   is_letter_or_number(document.characterAt(position)):
             position -= 1
         cursor = self._control.textCursor()
         cursor.setPosition(position + 1)
         return cursor
 
     def _get_word_end_cursor(self, position):
         """ Find the end of the word to the right the given position. If a
             sequence of non-word characters precedes the first word, skip over
             them. (This emulates the behavior of bash, emacs, etc.)
         """
         document = self._control.document()
         end = self._get_end_cursor().position()
         while position < end and \
                   not is_letter_or_number(document.characterAt(position)):
             position += 1
         while position < end and \
                   is_letter_or_number(document.characterAt(position)):
             position += 1
         cursor = self._control.textCursor()
         cursor.setPosition(position)
         return cursor
 
     def _insert_continuation_prompt(self, cursor):
         """ Inserts new continuation prompt using the specified cursor.
         """
         if self._continuation_prompt_html is None:
             self._insert_plain_text(cursor, self._continuation_prompt)
         else:
             self._continuation_prompt = self._insert_html_fetching_plain_text(
                 cursor, self._continuation_prompt_html)
 
     def _insert_block(self, cursor, block_format=None):
         """ Inserts an empty QTextBlock using the specified cursor.
         """
         if block_format is None:
             block_format = QtGui.QTextBlockFormat()
         cursor.insertBlock(block_format)
 
     def _insert_html(self, cursor, html):
         """ Inserts HTML using the specified cursor in such a way that future
             formatting is unaffected.
         """
         cursor.beginEditBlock()
         cursor.insertHtml(html)
 
         # After inserting HTML, the text document "remembers" it's in "html
         # mode", which means that subsequent calls adding plain text will result
         # in unwanted formatting, lost tab characters, etc. The following code
         # hacks around this behavior, which I consider to be a bug in Qt, by
         # (crudely) resetting the document's style state.
         cursor.movePosition(QtGui.QTextCursor.Left,
                             QtGui.QTextCursor.KeepAnchor)
         if cursor.selection().toPlainText() == ' ':
             cursor.removeSelectedText()
         else:
             cursor.movePosition(QtGui.QTextCursor.Right)
         cursor.insertText(' ', QtGui.QTextCharFormat())
         cursor.endEditBlock()
 
     def _insert_html_fetching_plain_text(self, cursor, html):
         """ Inserts HTML using the specified cursor, then returns its plain text
             version.
         """
         cursor.beginEditBlock()
         cursor.removeSelectedText()
 
         start = cursor.position()
         self._insert_html(cursor, html)
         end = cursor.position()
         cursor.setPosition(start, QtGui.QTextCursor.KeepAnchor)
         text = cursor.selection().toPlainText()
 
         cursor.setPosition(end)
         cursor.endEditBlock()
         return text
 
     def _insert_plain_text(self, cursor, text, flush=False):
         """ Inserts plain text using the specified cursor, processing ANSI codes
             if enabled.
         """
         # maximumBlockCount() can be different from self.buffer_size in
         # case input prompt is active.
         buffer_size = self._control.document().maximumBlockCount()
 
         if self._executing and not flush and \
                 self._pending_text_flush_interval.isActive():
             self._pending_insert_text.append(text)
             if buffer_size > 0:
                 self._pending_insert_text = self._get_last_lines_from_list(
                                         self._pending_insert_text, buffer_size)
             return
 
         if self._executing and not self._pending_text_flush_interval.isActive():
             self._pending_text_flush_interval.start()
 
         # Clip the text to last `buffer_size` lines.
         if buffer_size > 0:
             text = self._get_last_lines(text, buffer_size)
 
         cursor.beginEditBlock()
         if self.ansi_codes:
             for substring in self._ansi_processor.split_string(text):
                 for act in self._ansi_processor.actions:
 
                     # Unlike real terminal emulators, we don't distinguish
                     # between the screen and the scrollback buffer. A screen
                     # erase request clears everything.
                     if act.action == 'erase' and act.area == 'screen':
                         cursor.select(QtGui.QTextCursor.Document)
                         cursor.removeSelectedText()
 
                     # Simulate a form feed by scrolling just past the last line.
                     elif act.action == 'scroll' and act.unit == 'page':
                         cursor.insertText('\n')
                         cursor.endEditBlock()
                         self._set_top_cursor(cursor)
                         cursor.joinPreviousEditBlock()
                         cursor.deletePreviousChar()
 
                     elif act.action == 'carriage-return':
                         cursor.movePosition(
                             cursor.StartOfLine, cursor.KeepAnchor)
 
                     elif act.action == 'beep':
                         QtGui.qApp.beep()
 
                     elif act.action == 'backspace':
                         if not cursor.atBlockStart():
                             cursor.movePosition(
                                 cursor.PreviousCharacter, cursor.KeepAnchor)
 
                     elif act.action == 'newline':
                         cursor.movePosition(cursor.EndOfLine)
 
                 format = self._ansi_processor.get_format()
 
                 selection = cursor.selectedText()
                 if len(selection) == 0:
                     cursor.insertText(substring, format)
                 elif substring is not None:
                     # BS and CR are treated as a change in print
                     # position, rather than a backwards character
                     # deletion for output equivalence with (I)Python
                     # terminal.
                     if len(substring) >= len(selection):
                         cursor.insertText(substring, format)
                     else:
                         old_text = selection[len(substring):]
                         cursor.insertText(substring + old_text, format)
                         cursor.movePosition(cursor.PreviousCharacter,
                                cursor.KeepAnchor, len(old_text))
         else:
             cursor.insertText(text)
         cursor.endEditBlock()
 
     def _insert_plain_text_into_buffer(self, cursor, text):
         """ Inserts text into the input buffer using the specified cursor (which
             must be in the input buffer), ensuring that continuation prompts are
             inserted as necessary.
         """
         lines = text.splitlines(True)
         if lines:
             cursor.beginEditBlock()
             cursor.insertText(lines[0])
             for line in lines[1:]:
                 if self._continuation_prompt_html is None:
                     cursor.insertText(self._continuation_prompt)
                 else:
                     self._continuation_prompt = \
                         self._insert_html_fetching_plain_text(
                             cursor, self._continuation_prompt_html)
                 cursor.insertText(line)
             cursor.endEditBlock()
 
     def _in_buffer(self, position=None):
         """ Returns whether the current cursor (or, if specified, a position) is
             inside the editing region.
         """
         cursor = self._control.textCursor()
         if position is None:
             position = cursor.position()
         else:
             cursor.setPosition(position)
         line = cursor.blockNumber()
         prompt_line = self._get_prompt_cursor().blockNumber()
         if line == prompt_line:
             return position >= self._prompt_pos
         elif line > prompt_line:
             cursor.movePosition(QtGui.QTextCursor.StartOfBlock)
             prompt_pos = cursor.position() + len(self._continuation_prompt)
             return position >= prompt_pos
         return False
 
     def _keep_cursor_in_buffer(self):
         """ Ensures that the cursor is inside the editing region. Returns
             whether the cursor was moved.
         """
         moved = not self._in_buffer()
         if moved:
             cursor = self._control.textCursor()
             cursor.movePosition(QtGui.QTextCursor.End)
             self._control.setTextCursor(cursor)
         return moved
 
     def _keyboard_quit(self):
         """ Cancels the current editing task ala Ctrl-G in Emacs.
         """
         if self._temp_buffer_filled :
             self._cancel_completion()
             self._clear_temporary_buffer()
         else:
             self.input_buffer = ''
 
     def _page(self, text, html=False):
         """ Displays text using the pager if it exceeds the height of the
         viewport.
 
         Parameters:
         -----------
         html : bool, optional (default False)
             If set, the text will be interpreted as HTML instead of plain text.
         """
         line_height = QtGui.QFontMetrics(self.font).height()
         minlines = self._control.viewport().height() / line_height
         if self.paging != 'none' and \
                 re.match("(?:[^\n]*\n){%i}" % minlines, text):
             if self.paging == 'custom':
                 self.custom_page_requested.emit(text)
             else:
                 self._page_control.clear()
                 cursor = self._page_control.textCursor()
                 if html:
                     self._insert_html(cursor, text)
                 else:
                     self._insert_plain_text(cursor, text)
                 self._page_control.moveCursor(QtGui.QTextCursor.Start)
 
                 self._page_control.viewport().resize(self._control.size())
                 if self._splitter:
                     self._page_control.show()
                     self._page_control.setFocus()
                 else:
                     self.layout().setCurrentWidget(self._page_control)
         elif html:
             self._append_html(text)
         else:
             self._append_plain_text(text)
 
     def _set_paging(self, paging):
         """
         Change the pager to `paging` style.
 
         XXX: currently, this is limited to switching between 'hsplit' and
         'vsplit'.
 
         Parameters:
         -----------
         paging : string
             Either "hsplit", "vsplit", or "inside"
         """
         if self._splitter is None:
             raise NotImplementedError("""can only switch if --paging=hsplit or
                     --paging=vsplit is used.""")
         if paging == 'hsplit':
             self._splitter.setOrientation(QtCore.Qt.Horizontal)
         elif paging == 'vsplit':
             self._splitter.setOrientation(QtCore.Qt.Vertical)
         elif paging == 'inside':
             raise NotImplementedError("""switching to 'inside' paging not
                     supported yet.""")
         else:
             raise ValueError("unknown paging method '%s'" % paging)
         self.paging = paging
 
     def _prompt_finished(self):
         """ Called immediately after a prompt is finished, i.e. when some input
             will be processed and a new prompt displayed.
         """
         self._control.setReadOnly(True)
         self._prompt_finished_hook()
 
     def _prompt_started(self):
         """ Called immediately after a new prompt is displayed.
         """
         # Temporarily disable the maximum block count to permit undo/redo and
         # to ensure that the prompt position does not change due to truncation.
         self._control.document().setMaximumBlockCount(0)
         self._control.setUndoRedoEnabled(True)
 
         # Work around bug in QPlainTextEdit: input method is not re-enabled
         # when read-only is disabled.
         self._control.setReadOnly(False)
         self._control.setAttribute(QtCore.Qt.WA_InputMethodEnabled, True)
 
         if not self._reading:
             self._executing = False
         self._prompt_started_hook()
 
         # If the input buffer has changed while executing, load it.
         if self._input_buffer_pending:
             self.input_buffer = self._input_buffer_pending
             self._input_buffer_pending = ''
 
         self._control.moveCursor(QtGui.QTextCursor.End)
 
     def _readline(self, prompt='', callback=None):
         """ Reads one line of input from the user.
 
         Parameters
         ----------
         prompt : str, optional
             The prompt to print before reading the line.
 
         callback : callable, optional
             A callback to execute with the read line. If not specified, input is
             read *synchronously* and this method does not return until it has
             been read.
 
         Returns
         -------
         If a callback is specified, returns nothing. Otherwise, returns the
         input string with the trailing newline stripped.
         """
         if self._reading:
             raise RuntimeError('Cannot read a line. Widget is already reading.')
 
         if not callback and not self.isVisible():
             # If the user cannot see the widget, this function cannot return.
             raise RuntimeError('Cannot synchronously read a line if the widget '
                                'is not visible!')
 
         self._reading = True
         self._show_prompt(prompt, newline=False)
 
         if callback is None:
             self._reading_callback = None
             while self._reading:
                 QtCore.QCoreApplication.processEvents()
             return self._get_input_buffer(force=True).rstrip('\n')
 
         else:
             self._reading_callback = lambda: \
                 callback(self._get_input_buffer(force=True).rstrip('\n'))
 
     def _set_continuation_prompt(self, prompt, html=False):
         """ Sets the continuation prompt.
 
         Parameters
         ----------
         prompt : str
             The prompt to show when more input is needed.
 
         html : bool, optional (default False)
             If set, the prompt will be inserted as formatted HTML. Otherwise,
             the prompt will be treated as plain text, though ANSI color codes
             will be handled.
         """
         if html:
             self._continuation_prompt_html = prompt
         else:
             self._continuation_prompt = prompt
             self._continuation_prompt_html = None
 
     def _set_cursor(self, cursor):
         """ Convenience method to set the current cursor.
         """
         self._control.setTextCursor(cursor)
 
     def _set_top_cursor(self, cursor):
         """ Scrolls the viewport so that the specified cursor is at the top.
         """
         scrollbar = self._control.verticalScrollBar()
         scrollbar.setValue(scrollbar.maximum())
         original_cursor = self._control.textCursor()
         self._control.setTextCursor(cursor)
         self._control.ensureCursorVisible()
         self._control.setTextCursor(original_cursor)
 
     def _show_prompt(self, prompt=None, html=False, newline=True):
         """ Writes a new prompt at the end of the buffer.
 
         Parameters
         ----------
         prompt : str, optional
             The prompt to show. If not specified, the previous prompt is used.
 
         html : bool, optional (default False)
             Only relevant when a prompt is specified. If set, the prompt will
             be inserted as formatted HTML. Otherwise, the prompt will be treated
             as plain text, though ANSI color codes will be handled.
 
         newline : bool, optional (default True)
             If set, a new line will be written before showing the prompt if
             there is not already a newline at the end of the buffer.
         """
         # Save the current end position to support _append*(before_prompt=True).
         cursor = self._get_end_cursor()
         self._append_before_prompt_pos = cursor.position()
 
         # Insert a preliminary newline, if necessary.
         if newline and cursor.position() > 0:
             cursor.movePosition(QtGui.QTextCursor.Left,
                                 QtGui.QTextCursor.KeepAnchor)
             if cursor.selection().toPlainText() != '\n':
                 self._append_block()
 
         # Write the prompt.
         self._append_plain_text(self._prompt_sep)
         if prompt is None:
             if self._prompt_html is None:
                 self._append_plain_text(self._prompt)
             else:
                 self._append_html(self._prompt_html)
         else:
             if html:
                 self._prompt = self._append_html_fetching_plain_text(prompt)
                 self._prompt_html = prompt
             else:
                 self._append_plain_text(prompt)
                 self._prompt = prompt
                 self._prompt_html = None
 
         self._flush_pending_stream()
         self._prompt_pos = self._get_end_cursor().position()
         self._prompt_started()
 
     #------ Signal handlers ----------------------------------------------------
 
     def _adjust_scrollbars(self):
         """ Expands the vertical scrollbar beyond the range set by Qt.
         """
         # This code is adapted from _q_adjustScrollbars in qplaintextedit.cpp
         # and qtextedit.cpp.
         document = self._control.document()
         scrollbar = self._control.verticalScrollBar()
         viewport_height = self._control.viewport().height()
         if isinstance(self._control, QtGui.QPlainTextEdit):
             maximum = max(0, document.lineCount() - 1)
             step = viewport_height / self._control.fontMetrics().lineSpacing()
         else:
             # QTextEdit does not do line-based layout and blocks will not in
             # general have the same height. Therefore it does not make sense to
             # attempt to scroll in line height increments.
             maximum = document.size().height()
             step = viewport_height
         diff = maximum - scrollbar.maximum()
         scrollbar.setRange(0, maximum)
         scrollbar.setPageStep(step)
 
         # Compensate for undesirable scrolling that occurs automatically due to
         # maximumBlockCount() text truncation.
         if diff < 0 and document.blockCount() == document.maximumBlockCount():
             scrollbar.setValue(scrollbar.value() + diff)
 
     def _custom_context_menu_requested(self, pos):
         """ Shows a context menu at the given QPoint (in widget coordinates).
         """
         menu = self._context_menu_make(pos)
         menu.exec_(self._control.mapToGlobal(pos))

IPython/qt/kernel_mixins.py

@@ -1,220 +1,215 b''
 """ Defines a KernelManager that provides signals and slots.
 """
 
 # System library imports.
 from IPython.external.qt import QtCore
 
 # IPython imports.
 from IPython.utils.traitlets import HasTraits, Type
 from .util import MetaQObjectHasTraits, SuperQObject
 
 
 class ChannelQObject(SuperQObject):
 
     # Emitted when the channel is started.
     started = QtCore.Signal()
 
     # Emitted when the channel is stopped.
     stopped = QtCore.Signal()
 
     #---------------------------------------------------------------------------
     # Channel interface
     #---------------------------------------------------------------------------
 
     def start(self):
         """ Reimplemented to emit signal.
         """
         super(ChannelQObject, self).start()
         self.started.emit()
 
     def stop(self):
         """ Reimplemented to emit signal.
         """
         super(ChannelQObject, self).stop()
         self.stopped.emit()
 
     #---------------------------------------------------------------------------
     # InProcessChannel interface
     #---------------------------------------------------------------------------
 
     def call_handlers_later(self, *args, **kwds):
         """ Call the message handlers later.
         """
         do_later = lambda: self.call_handlers(*args, **kwds)
         QtCore.QTimer.singleShot(0, do_later)
 
     def process_events(self):
         """ Process any pending GUI events.
         """
         QtCore.QCoreApplication.instance().processEvents()
 
 
 class QtShellChannelMixin(ChannelQObject):
 
     # Emitted when any message is received.
     message_received = QtCore.Signal(object)
 
     # Emitted when a reply has been received for the corresponding request type.
     execute_reply = QtCore.Signal(object)
     complete_reply = QtCore.Signal(object)
     object_info_reply = QtCore.Signal(object)
     history_reply = QtCore.Signal(object)
 
     #---------------------------------------------------------------------------
     # 'ShellChannel' interface
     #---------------------------------------------------------------------------
 
     def call_handlers(self, msg):
         """ Reimplemented to emit signals instead of making callbacks.
         """
         # Emit the generic signal.
         self.message_received.emit(msg)
 
         # Emit signals for specialized message types.
         msg_type = msg['header']['msg_type']
         signal = getattr(self, msg_type, None)
         if signal:
             signal.emit(msg)
 
 
 class QtIOPubChannelMixin(ChannelQObject):
 
     # Emitted when any message is received.
     message_received = QtCore.Signal(object)
 
     # Emitted when a message of type 'stream' is received.
     stream_received = QtCore.Signal(object)
 
     # Emitted when a message of type 'pyin' is received.
     pyin_received = QtCore.Signal(object)
 
     # Emitted when a message of type 'pyout' is received.
     pyout_received = QtCore.Signal(object)
 
     # Emitted when a message of type 'pyerr' is received.
     pyerr_received = QtCore.Signal(object)
 
     # Emitted when a message of type 'display_data' is received
     display_data_received = QtCore.Signal(object)
 
     # Emitted when a crash report message is received from the kernel's
     # last-resort sys.excepthook.
     crash_received = QtCore.Signal(object)
 
     # Emitted when a shutdown is noticed.
     shutdown_reply_received = QtCore.Signal(object)
 
     #---------------------------------------------------------------------------
     # 'IOPubChannel' interface
     #---------------------------------------------------------------------------
 
     def call_handlers(self, msg):
         """ Reimplemented to emit signals instead of making callbacks.
         """
         # Emit the generic signal.
         self.message_received.emit(msg)
         # Emit signals for specialized message types.
         msg_type = msg['header']['msg_type']
         signal = getattr(self, msg_type + '_received', None)
         if signal:
             signal.emit(msg)
         elif msg_type in ('stdout', 'stderr'):
             self.stream_received.emit(msg)
 
     def flush(self):
         """ Reimplemented to ensure that signals are dispatched immediately.
         """
         super(QtIOPubChannelMixin, self).flush()
         QtCore.QCoreApplication.instance().processEvents()
 
 
 class QtStdInChannelMixin(ChannelQObject):
 
     # Emitted when any message is received.
     message_received = QtCore.Signal(object)
 
     # Emitted when an input request is received.
     input_requested = QtCore.Signal(object)
 
     #---------------------------------------------------------------------------
     # 'StdInChannel' interface
     #---------------------------------------------------------------------------
 
     def call_handlers(self, msg):
         """ Reimplemented to emit signals instead of making callbacks.
         """
         # Emit the generic signal.
         self.message_received.emit(msg)
 
         # Emit signals for specialized message types.
         msg_type = msg['header']['msg_type']
         if msg_type == 'input_request':
             self.input_requested.emit(msg)
 
 
 class QtHBChannelMixin(ChannelQObject):
 
     # Emitted when the kernel has died.
     kernel_died = QtCore.Signal(object)
 
     #---------------------------------------------------------------------------
     # 'HBChannel' interface
     #---------------------------------------------------------------------------
 
     def call_handlers(self, since_last_heartbeat):
         """ Reimplemented to emit signals instead of making callbacks.
         """
         # Emit the generic signal.
         self.kernel_died.emit(since_last_heartbeat)
 
 
-class QtKernelRestarterMixin(HasTraits, SuperQObject):
+class QtKernelRestarterMixin(MetaQObjectHasTraits('NewBase', (HasTraits, SuperQObject), {})):
 
-    __metaclass__ = MetaQObjectHasTraits
     _timer = None
 
 
-class QtKernelManagerMixin(HasTraits, SuperQObject):
+class QtKernelManagerMixin(MetaQObjectHasTraits('NewBase', (HasTraits, SuperQObject), {})):
     """ A KernelClient that provides signals and slots.
     """
 
-    __metaclass__ = MetaQObjectHasTraits
-
     kernel_restarted = QtCore.Signal()
 
 
-class QtKernelClientMixin(HasTraits, SuperQObject):
+class QtKernelClientMixin(MetaQObjectHasTraits('NewBase', (HasTraits, SuperQObject), {})):
     """ A KernelClient that provides signals and slots.
     """
 
-    __metaclass__ = MetaQObjectHasTraits
-
     # Emitted when the kernel client has started listening.
     started_channels = QtCore.Signal()
 
     # Emitted when the kernel client has stopped listening.
     stopped_channels = QtCore.Signal()
 
     # Use Qt-specific channel classes that emit signals.
     iopub_channel_class = Type(QtIOPubChannelMixin)
     shell_channel_class = Type(QtShellChannelMixin)
     stdin_channel_class = Type(QtStdInChannelMixin)
     hb_channel_class = Type(QtHBChannelMixin)
 
     #---------------------------------------------------------------------------
     # 'KernelClient' interface
     #---------------------------------------------------------------------------
 
     #------ Channel management -------------------------------------------------
 
     def start_channels(self, *args, **kw):
         """ Reimplemented to emit signal.
         """
         super(QtKernelClientMixin, self).start_channels(*args, **kw)
         self.started_channels.emit()
 
     def stop_channels(self):
         """ Reimplemented to emit signal.
         """
         super(QtKernelClientMixin, self).stop_channels()
         self.stopped_channels.emit()

IPython/utils/py3compat.py

@@ -1,210 +1,235 b''
 # coding: utf-8
 """Compatibility tricks for Python 3. Mainly to do with unicode."""
 import functools
 import sys
 import re
 import types
 
 from .encoding import DEFAULT_ENCODING
 
 orig_open = open
 
 def no_code(x, encoding=None):
     return x
 
 def decode(s, encoding=None):
     encoding = encoding or DEFAULT_ENCODING
     return s.decode(encoding, "replace")
 
 def encode(u, encoding=None):
     encoding = encoding or DEFAULT_ENCODING
     return u.encode(encoding, "replace")
 
 
 def cast_unicode(s, encoding=None):
     if isinstance(s, bytes):
         return decode(s, encoding)
     return s
 
 def cast_bytes(s, encoding=None):
     if not isinstance(s, bytes):
         return encode(s, encoding)
     return s
 
 def _modify_str_or_docstring(str_change_func):
     @functools.wraps(str_change_func)
     def wrapper(func_or_str):
         if isinstance(func_or_str, string_types):
             func = None
             doc = func_or_str
         else:
             func = func_or_str
             doc = func.__doc__
         
         doc = str_change_func(doc)
         
         if func:
             func.__doc__ = doc
             return func
         return doc
     return wrapper
 
 def safe_unicode(e):
     """unicode(e) with various fallbacks. Used for exceptions, which may not be
     safe to call unicode() on.
     """
     try:
         return unicode_type(e)
     except UnicodeError:
         pass
 
     try:
         return str_to_unicode(str(e))
     except UnicodeError:
         pass
 
     try:
         return str_to_unicode(repr(e))
     except UnicodeError:
         pass
 
     return u'Unrecoverably corrupt evalue'
 
 if sys.version_info[0] >= 3:
     PY3 = True
     
     input = input
     builtin_mod_name = "builtins"
     import builtins as builtin_mod
     
     str_to_unicode = no_code
     unicode_to_str = no_code
     str_to_bytes = encode
     bytes_to_str = decode
     cast_bytes_py2 = no_code
     
     string_types = (str,)
     unicode_type = str
     
     def isidentifier(s, dotted=False):
         if dotted:
             return all(isidentifier(a) for a in s.split("."))
         return s.isidentifier()
     
     open = orig_open
     xrange = range
     
     MethodType = types.MethodType
     
     def execfile(fname, glob, loc=None):
         loc = loc if (loc is not None) else glob
         with open(fname, 'rb') as f:
             exec(compile(f.read(), fname, 'exec'), glob, loc)
     
     # Refactor print statements in doctests.
     _print_statement_re = re.compile(r"\bprint (?P<expr>.*)$", re.MULTILINE)
     def _print_statement_sub(match):
         expr = match.groups('expr')
         return "print(%s)" % expr
     
     @_modify_str_or_docstring
     def doctest_refactor_print(doc):
         """Refactor 'print x' statements in a doctest to print(x) style. 2to3
         unfortunately doesn't pick up on our doctests.
         
         Can accept a string or a function, so it can be used as a decorator."""
         return _print_statement_re.sub(_print_statement_sub, doc)
     
     # Abstract u'abc' syntax:
     @_modify_str_or_docstring
     def u_format(s):
         """"{u}'abc'" --> "'abc'" (Python 3)
         
         Accepts a string or a function, so it can be used as a decorator."""
         return s.format(u='')
 
 else:
     PY3 = False
     
     input = raw_input
     builtin_mod_name = "__builtin__"
     import __builtin__ as builtin_mod
     
     str_to_unicode = decode
     unicode_to_str = encode
     str_to_bytes = no_code
     bytes_to_str = no_code
     cast_bytes_py2 = cast_bytes
     
     string_types = (str, unicode)
     unicode_type = unicode
     
     import re
     _name_re = re.compile(r"[a-zA-Z_][a-zA-Z0-9_]*$")
     def isidentifier(s, dotted=False):
         if dotted:
             return all(isidentifier(a) for a in s.split("."))
         return bool(_name_re.match(s))
     
     class open(object):
         """Wrapper providing key part of Python 3 open() interface."""
         def __init__(self, fname, mode="r", encoding="utf-8"):
             self.f = orig_open(fname, mode)
             self.enc = encoding
         
         def write(self, s):
             return self.f.write(s.encode(self.enc))
         
         def read(self, size=-1):
             return self.f.read(size).decode(self.enc)
         
         def close(self):
             return self.f.close()
         
         def __enter__(self):
             return self
         
         def __exit__(self, etype, value, traceback):
             self.f.close()
     
     xrange = xrange
 
     def MethodType(func, instance):
         return types.MethodType(func, instance, type(instance))
     
     # don't override system execfile on 2.x:
     execfile = execfile
     
     def doctest_refactor_print(func_or_str):
         return func_or_str
 
 
     # Abstract u'abc' syntax:
     @_modify_str_or_docstring
     def u_format(s):
         """"{u}'abc'" --> "u'abc'" (Python 2)
         
         Accepts a string or a function, so it can be used as a decorator."""
         return s.format(u='u')
 
     if sys.platform == 'win32':
         def execfile(fname, glob=None, loc=None):
             loc = loc if (loc is not None) else glob
             # The rstrip() is necessary b/c trailing whitespace in files will
             # cause an IndentationError in Python 2.6 (this was fixed in 2.7,
             # but we still support 2.6).  See issue 1027.
             scripttext = builtin_mod.open(fname).read().rstrip() + '\n'
             # compile converts unicode filename to str assuming
             # ascii. Let's do the conversion before calling compile
             if isinstance(fname, unicode):
                 filename = unicode_to_str(fname)
             else:
                 filename = fname
             exec(compile(scripttext, filename, 'exec'), glob, loc)
     else:
         def execfile(fname, *where):
             if isinstance(fname, unicode):
                 filename = fname.encode(sys.getfilesystemencoding())
             else:
                 filename = fname
             builtin_mod.execfile(filename, *where)
+
+# Parts below taken from six:
+# Copyright (c) 2010-2013 Benjamin Peterson
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+def with_metaclass(meta, *bases):
+    """Create a base class with a metaclass."""
+    return meta("NewBase", bases, {})

IPython/utils/traitlets.py

@@ -1,1439 +1,1437 b''
 # encoding: utf-8
 """
 A lightweight Traits like module.
 
 This is designed to provide a lightweight, simple, pure Python version of
 many of the capabilities of enthought.traits.  This includes:
 
 * Validation
 * Type specification with defaults
 * Static and dynamic notification
 * Basic predefined types
 * An API that is similar to enthought.traits
 
 We don't support:
 
 * Delegation
 * Automatic GUI generation
 * A full set of trait types.  Most importantly, we don't provide container
   traits (list, dict, tuple) that can trigger notifications if their
   contents change.
 * API compatibility with enthought.traits
 
 There are also some important difference in our design:
 
 * enthought.traits does not validate default values.  We do.
 
 We choose to create this module because we need these capabilities, but
 we need them to be pure Python so they work in all Python implementations,
 including Jython and IronPython.
 
 Inheritance diagram:
 
 .. inheritance-diagram:: IPython.utils.traitlets
    :parts: 3
 
 Authors:
 
 * Brian Granger
 * Enthought, Inc.  Some of the code in this file comes from enthought.traits
   and is licensed under the BSD license.  Also, many of the ideas also come
   from enthought.traits even though our implementation is very different.
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2011  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 
 import inspect
 import re
 import sys
 import types
 from types import FunctionType
 try:
     from types import ClassType, InstanceType
     ClassTypes = (ClassType, type)
 except:
     ClassTypes = (type,)
 
 from .importstring import import_item
 from IPython.utils import py3compat
 
 SequenceTypes = (list, tuple, set, frozenset)
 
 #-----------------------------------------------------------------------------
 # Basic classes
 #-----------------------------------------------------------------------------
 
 
 class NoDefaultSpecified ( object ): pass
 NoDefaultSpecified = NoDefaultSpecified()
 
 
 class Undefined ( object ): pass
 Undefined = Undefined()
 
 class TraitError(Exception):
     pass
 
 #-----------------------------------------------------------------------------
 # Utilities
 #-----------------------------------------------------------------------------
 
 
 def class_of ( object ):
     """ Returns a string containing the class name of an object with the
     correct indefinite article ('a' or 'an') preceding it (e.g., 'an Image',
     'a PlotValue').
     """
     if isinstance( object, py3compat.string_types ):
         return add_article( object )
 
     return add_article( object.__class__.__name__ )
 
 
 def add_article ( name ):
     """ Returns a string containing the correct indefinite article ('a' or 'an')
     prefixed to the specified string.
     """
     if name[:1].lower() in 'aeiou':
        return 'an ' + name
 
     return 'a ' + name
 
 
 def repr_type(obj):
     """ Return a string representation of a value and its type for readable
     error messages.
     """
     the_type = type(obj)
     if (not py3compat.PY3) and the_type is InstanceType:
         # Old-style class.
         the_type = obj.__class__
     msg = '%r %r' % (obj, the_type)
     return msg
 
 
 def is_trait(t):
     """ Returns whether the given value is an instance or subclass of TraitType.
     """
     return (isinstance(t, TraitType) or
             (isinstance(t, type) and issubclass(t, TraitType)))
 
 
 def parse_notifier_name(name):
     """Convert the name argument to a list of names.
 
     Examples
     --------
 
     >>> parse_notifier_name('a')
     ['a']
     >>> parse_notifier_name(['a','b'])
     ['a', 'b']
     >>> parse_notifier_name(None)
     ['anytrait']
     """
     if isinstance(name, str):
         return [name]
     elif name is None:
         return ['anytrait']
     elif isinstance(name, (list, tuple)):
         for n in name:
             assert isinstance(n, str), "names must be strings"
         return name
 
 
 class _SimpleTest:
     def __init__ ( self, value ): self.value = value
     def __call__ ( self, test  ):
         return test == self.value
     def __repr__(self):
         return "<SimpleTest(%r)" % self.value
     def __str__(self):
         return self.__repr__()
 
 
 def getmembers(object, predicate=None):
     """A safe version of inspect.getmembers that handles missing attributes.
 
     This is useful when there are descriptor based attributes that for
     some reason raise AttributeError even though they exist.  This happens
     in zope.inteface with the __provides__ attribute.
     """
     results = []
     for key in dir(object):
         try:
             value = getattr(object, key)
         except AttributeError:
             pass
         else:
             if not predicate or predicate(value):
                 results.append((key, value))
     results.sort()
     return results
 
 
 #-----------------------------------------------------------------------------
 # Base TraitType for all traits
 #-----------------------------------------------------------------------------
 
 
 class TraitType(object):
     """A base class for all trait descriptors.
 
     Notes
     -----
     Our implementation of traits is based on Python's descriptor
     prototol.  This class is the base class for all such descriptors.  The
     only magic we use is a custom metaclass for the main :class:`HasTraits`
     class that does the following:
 
     1. Sets the :attr:`name` attribute of every :class:`TraitType`
        instance in the class dict to the name of the attribute.
     2. Sets the :attr:`this_class` attribute of every :class:`TraitType`
        instance in the class dict to the *class* that declared the trait.
        This is used by the :class:`This` trait to allow subclasses to
        accept superclasses for :class:`This` values.
     """
 
 
     metadata = {}
     default_value = Undefined
     info_text = 'any value'
 
     def __init__(self, default_value=NoDefaultSpecified, **metadata):
         """Create a TraitType.
         """
         if default_value is not NoDefaultSpecified:
             self.default_value = default_value
 
         if len(metadata) > 0:
             if len(self.metadata) > 0:
                 self._metadata = self.metadata.copy()
                 self._metadata.update(metadata)
             else:
                 self._metadata = metadata
         else:
             self._metadata = self.metadata
 
         self.init()
 
     def init(self):
         pass
 
     def get_default_value(self):
         """Create a new instance of the default value."""
         return self.default_value
 
     def instance_init(self, obj):
         """This is called by :meth:`HasTraits.__new__` to finish init'ing.
 
         Some stages of initialization must be delayed until the parent
         :class:`HasTraits` instance has been created.  This method is
         called in :meth:`HasTraits.__new__` after the instance has been
         created.
 
         This method trigger the creation and validation of default values
         and also things like the resolution of str given class names in
         :class:`Type` and :class`Instance`.
 
         Parameters
         ----------
         obj : :class:`HasTraits` instance
             The parent :class:`HasTraits` instance that has just been
             created.
         """
         self.set_default_value(obj)
 
     def set_default_value(self, obj):
         """Set the default value on a per instance basis.
 
         This method is called by :meth:`instance_init` to create and
         validate the default value.  The creation and validation of
         default values must be delayed until the parent :class:`HasTraits`
         class has been instantiated.
         """
         # Check for a deferred initializer defined in the same class as the
         # trait declaration or above.
         mro = type(obj).mro()
         meth_name = '_%s_default' % self.name
         for cls in mro[:mro.index(self.this_class)+1]:
             if meth_name in cls.__dict__:
                 break
         else:
             # We didn't find one. Do static initialization.
             dv = self.get_default_value()
             newdv = self._validate(obj, dv)
             obj._trait_values[self.name] = newdv
             return
         # Complete the dynamic initialization.
         obj._trait_dyn_inits[self.name] = cls.__dict__[meth_name]
 
     def __get__(self, obj, cls=None):
         """Get the value of the trait by self.name for the instance.
 
         Default values are instantiated when :meth:`HasTraits.__new__`
         is called.  Thus by the time this method gets called either the
         default value or a user defined value (they called :meth:`__set__`)
         is in the :class:`HasTraits` instance.
         """
         if obj is None:
             return self
         else:
             try:
                 value = obj._trait_values[self.name]
             except KeyError:
                 # Check for a dynamic initializer.
                 if self.name in obj._trait_dyn_inits:
                     value = obj._trait_dyn_inits[self.name](obj)
                     # FIXME: Do we really validate here?
                     value = self._validate(obj, value)
                     obj._trait_values[self.name] = value
                     return value
                 else:
                     raise TraitError('Unexpected error in TraitType: '
                         'both default value and dynamic initializer are '
                         'absent.')
             except Exception:
                 # HasTraits should call set_default_value to populate
                 # this.  So this should never be reached.
                 raise TraitError('Unexpected error in TraitType: '
                                     'default value not set properly')
             else:
                 return value
 
     def __set__(self, obj, value):
         new_value = self._validate(obj, value)
         old_value = self.__get__(obj)
         obj._trait_values[self.name] = new_value
         if old_value != new_value:
             obj._notify_trait(self.name, old_value, new_value)
 
     def _validate(self, obj, value):
         if hasattr(self, 'validate'):
             return self.validate(obj, value)
         elif hasattr(self, 'is_valid_for'):
             valid = self.is_valid_for(value)
             if valid:
                 return value
             else:
                 raise TraitError('invalid value for type: %r' % value)
         elif hasattr(self, 'value_for'):
             return self.value_for(value)
         else:
             return value
 
     def info(self):
         return self.info_text
 
     def error(self, obj, value):
         if obj is not None:
             e = "The '%s' trait of %s instance must be %s, but a value of %s was specified." \
                 % (self.name, class_of(obj),
                    self.info(), repr_type(value))
         else:
             e = "The '%s' trait must be %s, but a value of %r was specified." \
                 % (self.name, self.info(), repr_type(value))
         raise TraitError(e)
 
     def get_metadata(self, key):
         return getattr(self, '_metadata', {}).get(key, None)
 
     def set_metadata(self, key, value):
         getattr(self, '_metadata', {})[key] = value
 
 
 #-----------------------------------------------------------------------------
 # The HasTraits implementation
 #-----------------------------------------------------------------------------
 
 
 class MetaHasTraits(type):
     """A metaclass for HasTraits.
 
     This metaclass makes sure that any TraitType class attributes are
     instantiated and sets their name attribute.
     """
 
     def __new__(mcls, name, bases, classdict):
         """Create the HasTraits class.
 
         This instantiates all TraitTypes in the class dict and sets their
         :attr:`name` attribute.
         """
         # print "MetaHasTraitlets (mcls, name): ", mcls, name
         # print "MetaHasTraitlets (bases): ", bases
         # print "MetaHasTraitlets (classdict): ", classdict
         for k,v in classdict.iteritems():
             if isinstance(v, TraitType):
                 v.name = k
             elif inspect.isclass(v):
                 if issubclass(v, TraitType):
                     vinst = v()
                     vinst.name = k
                     classdict[k] = vinst
         return super(MetaHasTraits, mcls).__new__(mcls, name, bases, classdict)
 
     def __init__(cls, name, bases, classdict):
         """Finish initializing the HasTraits class.
 
         This sets the :attr:`this_class` attribute of each TraitType in the
         class dict to the newly created class ``cls``.
         """
         for k, v in classdict.iteritems():
             if isinstance(v, TraitType):
                 v.this_class = cls
         super(MetaHasTraits, cls).__init__(name, bases, classdict)
 
-class HasTraits(object):
-
-    __metaclass__ = MetaHasTraits
+class HasTraits(py3compat.with_metaclass(MetaHasTraits, object)):
 
     def __new__(cls, *args, **kw):
         # This is needed because in Python 2.6 object.__new__ only accepts
         # the cls argument.
         new_meth = super(HasTraits, cls).__new__
         if new_meth is object.__new__:
             inst = new_meth(cls)
         else:
             inst = new_meth(cls, **kw)
         inst._trait_values = {}
         inst._trait_notifiers = {}
         inst._trait_dyn_inits = {}
         # Here we tell all the TraitType instances to set their default
         # values on the instance.
         for key in dir(cls):
             # Some descriptors raise AttributeError like zope.interface's
             # __provides__ attributes even though they exist.  This causes
             # AttributeErrors even though they are listed in dir(cls).
             try:
                 value = getattr(cls, key)
             except AttributeError:
                 pass
             else:
                 if isinstance(value, TraitType):
                     value.instance_init(inst)
 
         return inst
 
     def __init__(self, *args, **kw):
         # Allow trait values to be set using keyword arguments.
         # We need to use setattr for this to trigger validation and
         # notifications.
         for key, value in kw.iteritems():
             setattr(self, key, value)
 
     def _notify_trait(self, name, old_value, new_value):
 
         # First dynamic ones
         callables = []
         callables.extend(self._trait_notifiers.get(name,[]))
         callables.extend(self._trait_notifiers.get('anytrait',[]))
 
         # Now static ones
         try:
             cb = getattr(self, '_%s_changed' % name)
         except:
             pass
         else:
             callables.append(cb)
 
         # Call them all now
         for c in callables:
             # Traits catches and logs errors here.  I allow them to raise
             if callable(c):
                 argspec = inspect.getargspec(c)
                 nargs = len(argspec[0])
                 # Bound methods have an additional 'self' argument
                 # I don't know how to treat unbound methods, but they
                 # can't really be used for callbacks.
                 if isinstance(c, types.MethodType):
                     offset = -1
                 else:
                     offset = 0
                 if nargs + offset == 0:
                     c()
                 elif nargs + offset == 1:
                     c(name)
                 elif nargs + offset == 2:
                     c(name, new_value)
                 elif nargs + offset == 3:
                     c(name, old_value, new_value)
                 else:
                     raise TraitError('a trait changed callback '
                                         'must have 0-3 arguments.')
             else:
                 raise TraitError('a trait changed callback '
                                     'must be callable.')
 
 
     def _add_notifiers(self, handler, name):
         if name not in self._trait_notifiers:
             nlist = []
             self._trait_notifiers[name] = nlist
         else:
             nlist = self._trait_notifiers[name]
         if handler not in nlist:
             nlist.append(handler)
 
     def _remove_notifiers(self, handler, name):
         if name in self._trait_notifiers:
             nlist = self._trait_notifiers[name]
             try:
                 index = nlist.index(handler)
             except ValueError:
                 pass
             else:
                 del nlist[index]
 
     def on_trait_change(self, handler, name=None, remove=False):
         """Setup a handler to be called when a trait changes.
 
         This is used to setup dynamic notifications of trait changes.
 
         Static handlers can be created by creating methods on a HasTraits
         subclass with the naming convention '_[traitname]_changed'.  Thus,
         to create static handler for the trait 'a', create the method
         _a_changed(self, name, old, new) (fewer arguments can be used, see
         below).
 
         Parameters
         ----------
         handler : callable
             A callable that is called when a trait changes.  Its
             signature can be handler(), handler(name), handler(name, new)
             or handler(name, old, new).
         name : list, str, None
             If None, the handler will apply to all traits.  If a list
             of str, handler will apply to all names in the list.  If a
             str, the handler will apply just to that name.
         remove : bool
             If False (the default), then install the handler.  If True
             then unintall it.
         """
         if remove:
             names = parse_notifier_name(name)
             for n in names:
                 self._remove_notifiers(handler, n)
         else:
             names = parse_notifier_name(name)
             for n in names:
                 self._add_notifiers(handler, n)
 
     @classmethod
     def class_trait_names(cls, **metadata):
         """Get a list of all the names of this classes traits.
 
         This method is just like the :meth:`trait_names` method, but is unbound.
         """
         return cls.class_traits(**metadata).keys()
 
     @classmethod
     def class_traits(cls, **metadata):
         """Get a list of all the traits of this class.
 
         This method is just like the :meth:`traits` method, but is unbound.
 
         The TraitTypes returned don't know anything about the values
         that the various HasTrait's instances are holding.
 
         This follows the same algorithm as traits does and does not allow
         for any simple way of specifying merely that a metadata name
         exists, but has any value.  This is because get_metadata returns
         None if a metadata key doesn't exist.
         """
         traits = dict([memb for memb in getmembers(cls) if \
                      isinstance(memb[1], TraitType)])
 
         if len(metadata) == 0:
             return traits
 
         for meta_name, meta_eval in metadata.items():
             if type(meta_eval) is not FunctionType:
                 metadata[meta_name] = _SimpleTest(meta_eval)
 
         result = {}
         for name, trait in traits.items():
             for meta_name, meta_eval in metadata.items():
                 if not meta_eval(trait.get_metadata(meta_name)):
                     break
             else:
                 result[name] = trait
 
         return result
 
     def trait_names(self, **metadata):
         """Get a list of all the names of this classes traits."""
         return self.traits(**metadata).keys()
 
     def traits(self, **metadata):
         """Get a list of all the traits of this class.
 
         The TraitTypes returned don't know anything about the values
         that the various HasTrait's instances are holding.
 
         This follows the same algorithm as traits does and does not allow
         for any simple way of specifying merely that a metadata name
         exists, but has any value.  This is because get_metadata returns
         None if a metadata key doesn't exist.
         """
         traits = dict([memb for memb in getmembers(self.__class__) if \
                      isinstance(memb[1], TraitType)])
 
         if len(metadata) == 0:
             return traits
 
         for meta_name, meta_eval in metadata.items():
             if type(meta_eval) is not FunctionType:
                 metadata[meta_name] = _SimpleTest(meta_eval)
 
         result = {}
         for name, trait in traits.items():
             for meta_name, meta_eval in metadata.items():
                 if not meta_eval(trait.get_metadata(meta_name)):
                     break
             else:
                 result[name] = trait
 
         return result
 
     def trait_metadata(self, traitname, key):
         """Get metadata values for trait by key."""
         try:
             trait = getattr(self.__class__, traitname)
         except AttributeError:
             raise TraitError("Class %s does not have a trait named %s" %
                                 (self.__class__.__name__, traitname))
         else:
             return trait.get_metadata(key)
 
 #-----------------------------------------------------------------------------
 # Actual TraitTypes implementations/subclasses
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # TraitTypes subclasses for handling classes and instances of classes
 #-----------------------------------------------------------------------------
 
 
 class ClassBasedTraitType(TraitType):
     """A trait with error reporting for Type, Instance and This."""
 
     def error(self, obj, value):
         kind = type(value)
         if (not py3compat.PY3) and kind is InstanceType:
             msg = 'class %s' % value.__class__.__name__
         else:
             msg = '%s (i.e. %s)' % ( str( kind )[1:-1], repr( value ) )
 
         if obj is not None:
             e = "The '%s' trait of %s instance must be %s, but a value of %s was specified." \
                 % (self.name, class_of(obj),
                    self.info(), msg)
         else:
             e = "The '%s' trait must be %s, but a value of %r was specified." \
                 % (self.name, self.info(), msg)
 
         raise TraitError(e)
 
 
 class Type(ClassBasedTraitType):
     """A trait whose value must be a subclass of a specified class."""
 
     def __init__ (self, default_value=None, klass=None, allow_none=True, **metadata ):
         """Construct a Type trait
 
         A Type trait specifies that its values must be subclasses of
         a particular class.
 
         If only ``default_value`` is given, it is used for the ``klass`` as
         well.
 
         Parameters
         ----------
         default_value : class, str or None
             The default value must be a subclass of klass.  If an str,
             the str must be a fully specified class name, like 'foo.bar.Bah'.
             The string is resolved into real class, when the parent
             :class:`HasTraits` class is instantiated.
         klass : class, str, None
             Values of this trait must be a subclass of klass.  The klass
             may be specified in a string like: 'foo.bar.MyClass'.
             The string is resolved into real class, when the parent
             :class:`HasTraits` class is instantiated.
         allow_none : boolean
             Indicates whether None is allowed as an assignable value. Even if
             ``False``, the default value may be ``None``.
         """
         if default_value is None:
             if klass is None:
                 klass = object
         elif klass is None:
             klass = default_value
 
         if not (inspect.isclass(klass) or isinstance(klass, py3compat.string_types)):
             raise TraitError("A Type trait must specify a class.")
 
         self.klass       = klass
         self._allow_none = allow_none
 
         super(Type, self).__init__(default_value, **metadata)
 
     def validate(self, obj, value):
         """Validates that the value is a valid object instance."""
         try:
             if issubclass(value, self.klass):
                 return value
         except:
             if (value is None) and (self._allow_none):
                 return value
 
         self.error(obj, value)
 
     def info(self):
         """ Returns a description of the trait."""
         if isinstance(self.klass, py3compat.string_types):
             klass = self.klass
         else:
             klass = self.klass.__name__
         result = 'a subclass of ' + klass
         if self._allow_none:
             return result + ' or None'
         return result
 
     def instance_init(self, obj):
         self._resolve_classes()
         super(Type, self).instance_init(obj)
 
     def _resolve_classes(self):
         if isinstance(self.klass, py3compat.string_types):
             self.klass = import_item(self.klass)
         if isinstance(self.default_value, py3compat.string_types):
             self.default_value = import_item(self.default_value)
 
     def get_default_value(self):
         return self.default_value
 
 
 class DefaultValueGenerator(object):
     """A class for generating new default value instances."""
 
     def __init__(self, *args, **kw):
         self.args = args
         self.kw = kw
 
     def generate(self, klass):
         return klass(*self.args, **self.kw)
 
 
 class Instance(ClassBasedTraitType):
     """A trait whose value must be an instance of a specified class.
 
     The value can also be an instance of a subclass of the specified class.
     """
 
     def __init__(self, klass=None, args=None, kw=None,
                  allow_none=True, **metadata ):
         """Construct an Instance trait.
 
         This trait allows values that are instances of a particular
         class or its sublclasses.  Our implementation is quite different
         from that of enthough.traits as we don't allow instances to be used
         for klass and we handle the ``args`` and ``kw`` arguments differently.
 
         Parameters
         ----------
         klass : class, str
             The class that forms the basis for the trait.  Class names
             can also be specified as strings, like 'foo.bar.Bar'.
         args : tuple
             Positional arguments for generating the default value.
         kw : dict
             Keyword arguments for generating the default value.
         allow_none : bool
             Indicates whether None is allowed as a value.
 
         Default Value
         -------------
         If both ``args`` and ``kw`` are None, then the default value is None.
         If ``args`` is a tuple and ``kw`` is a dict, then the default is
         created as ``klass(*args, **kw)``.  If either ``args`` or ``kw`` is
         not (but not both), None is replace by ``()`` or ``{}``.
         """
 
         self._allow_none = allow_none
 
         if (klass is None) or (not (inspect.isclass(klass) or isinstance(klass, py3compat.string_types))):
             raise TraitError('The klass argument must be a class'
                                 ' you gave: %r' % klass)
         self.klass = klass
 
         # self.klass is a class, so handle default_value
         if args is None and kw is None:
             default_value = None
         else:
             if args is None:
                 # kw is not None
                 args = ()
             elif kw is None:
                 # args is not None
                 kw = {}
 
             if not isinstance(kw, dict):
                 raise TraitError("The 'kw' argument must be a dict or None.")
             if not isinstance(args, tuple):
                 raise TraitError("The 'args' argument must be a tuple or None.")
 
             default_value = DefaultValueGenerator(*args, **kw)
 
         super(Instance, self).__init__(default_value, **metadata)
 
     def validate(self, obj, value):
         if value is None:
             if self._allow_none:
                 return value
             self.error(obj, value)
 
         if isinstance(value, self.klass):
             return value
         else:
             self.error(obj, value)
 
     def info(self):
         if isinstance(self.klass, py3compat.string_types):
             klass = self.klass
         else:
             klass = self.klass.__name__
         result = class_of(klass)
         if self._allow_none:
             return result + ' or None'
 
         return result
 
     def instance_init(self, obj):
         self._resolve_classes()
         super(Instance, self).instance_init(obj)
 
     def _resolve_classes(self):
         if isinstance(self.klass, py3compat.string_types):
             self.klass = import_item(self.klass)
 
     def get_default_value(self):
         """Instantiate a default value instance.
 
         This is called when the containing HasTraits classes'
         :meth:`__new__` method is called to ensure that a unique instance
         is created for each HasTraits instance.
         """
         dv  = self.default_value
         if isinstance(dv, DefaultValueGenerator):
             return dv.generate(self.klass)
         else:
             return dv
 
 
 class This(ClassBasedTraitType):
     """A trait for instances of the class containing this trait.
 
     Because how how and when class bodies are executed, the ``This``
     trait can only have a default value of None.  This, and because we
     always validate default values, ``allow_none`` is *always* true.
     """
 
     info_text = 'an instance of the same type as the receiver or None'
 
     def __init__(self, **metadata):
         super(This, self).__init__(None, **metadata)
 
     def validate(self, obj, value):
         # What if value is a superclass of obj.__class__?  This is
         # complicated if it was the superclass that defined the This
         # trait.
         if isinstance(value, self.this_class) or (value is None):
             return value
         else:
             self.error(obj, value)
 
 
 #-----------------------------------------------------------------------------
 # Basic TraitTypes implementations/subclasses
 #-----------------------------------------------------------------------------
 
 
 class Any(TraitType):
     default_value = None
     info_text = 'any value'
 
 
 class Int(TraitType):
     """An int trait."""
 
     default_value = 0
     info_text = 'an int'
 
     def validate(self, obj, value):
         if isinstance(value, int):
             return value
         self.error(obj, value)
 
 class CInt(Int):
     """A casting version of the int trait."""
 
     def validate(self, obj, value):
         try:
             return int(value)
         except:
             self.error(obj, value)
 
 if py3compat.PY3:
     Long, CLong = Int, CInt
     Integer = Int
 else:
     class Long(TraitType):
         """A long integer trait."""
 
         default_value = 0
         info_text = 'a long'
 
         def validate(self, obj, value):
             if isinstance(value, long):
                 return value
             if isinstance(value, int):
                 return long(value)
             self.error(obj, value)
 
 
     class CLong(Long):
         """A casting version of the long integer trait."""
 
         def validate(self, obj, value):
             try:
                 return long(value)
             except:
                 self.error(obj, value)
 
     class Integer(TraitType):
         """An integer trait.
 
         Longs that are unnecessary (<= sys.maxint) are cast to ints."""
 
         default_value = 0
         info_text = 'an integer'
 
         def validate(self, obj, value):
             if isinstance(value, int):
                 return value
             if isinstance(value, long):
                 # downcast longs that fit in int:
                 # note that int(n > sys.maxint) returns a long, so
                 # we don't need a condition on this cast
                 return int(value)
             if sys.platform == "cli":
                 from System import Int64
                 if isinstance(value, Int64):
                     return int(value)
             self.error(obj, value)
 
 
 class Float(TraitType):
     """A float trait."""
 
     default_value = 0.0
     info_text = 'a float'
 
     def validate(self, obj, value):
         if isinstance(value, float):
             return value
         if isinstance(value, int):
             return float(value)
         self.error(obj, value)
 
 
 class CFloat(Float):
     """A casting version of the float trait."""
 
     def validate(self, obj, value):
         try:
             return float(value)
         except:
             self.error(obj, value)
 
 class Complex(TraitType):
     """A trait for complex numbers."""
 
     default_value = 0.0 + 0.0j
     info_text = 'a complex number'
 
     def validate(self, obj, value):
         if isinstance(value, complex):
             return value
         if isinstance(value, (float, int)):
             return complex(value)
         self.error(obj, value)
 
 
 class CComplex(Complex):
     """A casting version of the complex number trait."""
 
     def validate (self, obj, value):
         try:
             return complex(value)
         except:
             self.error(obj, value)
 
 # We should always be explicit about whether we're using bytes or unicode, both
 # for Python 3 conversion and for reliable unicode behaviour on Python 2. So
 # we don't have a Str type.
 class Bytes(TraitType):
     """A trait for byte strings."""
 
     default_value = b''
     info_text = 'a string'
 
     def validate(self, obj, value):
         if isinstance(value, bytes):
             return value
         self.error(obj, value)
 
 
 class CBytes(Bytes):
     """A casting version of the byte string trait."""
 
     def validate(self, obj, value):
         try:
             return bytes(value)
         except:
             self.error(obj, value)
 
 
 class Unicode(TraitType):
     """A trait for unicode strings."""
 
     default_value = u''
     info_text = 'a unicode string'
 
     def validate(self, obj, value):
         if isinstance(value, py3compat.unicode_type):
             return value
         if isinstance(value, bytes):
             return py3compat.unicode_type(value)
         self.error(obj, value)
 
 
 class CUnicode(Unicode):
     """A casting version of the unicode trait."""
 
     def validate(self, obj, value):
         try:
             return py3compat.unicode_type(value)
         except:
             self.error(obj, value)
 
 
 class ObjectName(TraitType):
     """A string holding a valid object name in this version of Python.
 
     This does not check that the name exists in any scope."""
     info_text = "a valid object identifier in Python"
 
     if py3compat.PY3:
         # Python 3:
         coerce_str = staticmethod(lambda _,s: s)
 
     else:
         # Python 2:
         def coerce_str(self, obj, value):
             "In Python 2, coerce ascii-only unicode to str"
             if isinstance(value, unicode):
                 try:
                     return str(value)
                 except UnicodeEncodeError:
                     self.error(obj, value)
             return value
 
     def validate(self, obj, value):
         value = self.coerce_str(obj, value)
 
         if isinstance(value, str) and py3compat.isidentifier(value):
             return value
         self.error(obj, value)
 
 class DottedObjectName(ObjectName):
     """A string holding a valid dotted object name in Python, such as A.b3._c"""
     def validate(self, obj, value):
         value = self.coerce_str(obj, value)
 
         if isinstance(value, str) and py3compat.isidentifier(value, dotted=True):
             return value
         self.error(obj, value)
 
 
 class Bool(TraitType):
     """A boolean (True, False) trait."""
 
     default_value = False
     info_text = 'a boolean'
 
     def validate(self, obj, value):
         if isinstance(value, bool):
             return value
         self.error(obj, value)
 
 
 class CBool(Bool):
     """A casting version of the boolean trait."""
 
     def validate(self, obj, value):
         try:
             return bool(value)
         except:
             self.error(obj, value)
 
 
 class Enum(TraitType):
     """An enum that whose value must be in a given sequence."""
 
     def __init__(self, values, default_value=None, allow_none=True, **metadata):
         self.values = values
         self._allow_none = allow_none
         super(Enum, self).__init__(default_value, **metadata)
 
     def validate(self, obj, value):
         if value is None:
             if self._allow_none:
                 return value
 
         if value in self.values:
                 return value
         self.error(obj, value)
 
     def info(self):
         """ Returns a description of the trait."""
         result = 'any of ' + repr(self.values)
         if self._allow_none:
             return result + ' or None'
         return result
 
 class CaselessStrEnum(Enum):
     """An enum of strings that are caseless in validate."""
 
     def validate(self, obj, value):
         if value is None:
             if self._allow_none:
                 return value
 
         if not isinstance(value, py3compat.string_types):
             self.error(obj, value)
 
         for v in self.values:
             if v.lower() == value.lower():
                 return v
         self.error(obj, value)
 
 class Container(Instance):
     """An instance of a container (list, set, etc.)
 
     To be subclassed by overriding klass.
     """
     klass = None
     _valid_defaults = SequenceTypes
     _trait = None
 
     def __init__(self, trait=None, default_value=None, allow_none=True,
                 **metadata):
         """Create a container trait type from a list, set, or tuple.
 
         The default value is created by doing ``List(default_value)``,
         which creates a copy of the ``default_value``.
 
         ``trait`` can be specified, which restricts the type of elements
         in the container to that TraitType.
 
         If only one arg is given and it is not a Trait, it is taken as
         ``default_value``:
 
         ``c = List([1,2,3])``
 
         Parameters
         ----------
 
         trait : TraitType [ optional ]
             the type for restricting the contents of the Container.  If unspecified,
             types are not checked.
 
         default_value : SequenceType [ optional ]
             The default value for the Trait.  Must be list/tuple/set, and
             will be cast to the container type.
 
         allow_none : Bool [ default True ]
             Whether to allow the value to be None
 
         **metadata : any
             further keys for extensions to the Trait (e.g. config)
 
         """
         # allow List([values]):
         if default_value is None and not is_trait(trait):
             default_value = trait
             trait = None
 
         if default_value is None:
             args = ()
         elif isinstance(default_value, self._valid_defaults):
             args = (default_value,)
         else:
             raise TypeError('default value of %s was %s' %(self.__class__.__name__, default_value))
 
         if is_trait(trait):
             self._trait = trait() if isinstance(trait, type) else trait
             self._trait.name = 'element'
         elif trait is not None:
             raise TypeError("`trait` must be a Trait or None, got %s"%repr_type(trait))
 
         super(Container,self).__init__(klass=self.klass, args=args,
                                   allow_none=allow_none, **metadata)
 
     def element_error(self, obj, element, validator):
         e = "Element of the '%s' trait of %s instance must be %s, but a value of %s was specified." \
             % (self.name, class_of(obj), validator.info(), repr_type(element))
         raise TraitError(e)
 
     def validate(self, obj, value):
         value = super(Container, self).validate(obj, value)
         if value is None:
             return value
 
         value = self.validate_elements(obj, value)
 
         return value
 
     def validate_elements(self, obj, value):
         validated = []
         if self._trait is None or isinstance(self._trait, Any):
             return value
         for v in value:
             try:
                 v = self._trait.validate(obj, v)
             except TraitError:
                 self.element_error(obj, v, self._trait)
             else:
                 validated.append(v)
         return self.klass(validated)
 
 
 class List(Container):
     """An instance of a Python list."""
     klass = list
 
     def __init__(self, trait=None, default_value=None, minlen=0, maxlen=sys.maxsize,
                 allow_none=True, **metadata):
         """Create a List trait type from a list, set, or tuple.
 
         The default value is created by doing ``List(default_value)``,
         which creates a copy of the ``default_value``.
 
         ``trait`` can be specified, which restricts the type of elements
         in the container to that TraitType.
 
         If only one arg is given and it is not a Trait, it is taken as
         ``default_value``:
 
         ``c = List([1,2,3])``
 
         Parameters
         ----------
 
         trait : TraitType [ optional ]
             the type for restricting the contents of the Container.  If unspecified,
             types are not checked.
 
         default_value : SequenceType [ optional ]
             The default value for the Trait.  Must be list/tuple/set, and
             will be cast to the container type.
 
         minlen : Int [ default 0 ]
             The minimum length of the input list
 
         maxlen : Int [ default sys.maxsize ]
             The maximum length of the input list
 
         allow_none : Bool [ default True ]
             Whether to allow the value to be None
 
         **metadata : any
             further keys for extensions to the Trait (e.g. config)
 
         """
         self._minlen = minlen
         self._maxlen = maxlen
         super(List, self).__init__(trait=trait, default_value=default_value,
                                 allow_none=allow_none, **metadata)
 
     def length_error(self, obj, value):
         e = "The '%s' trait of %s instance must be of length %i <= L <= %i, but a value of %s was specified." \
             % (self.name, class_of(obj), self._minlen, self._maxlen, value)
         raise TraitError(e)
 
     def validate_elements(self, obj, value):
         length = len(value)
         if length < self._minlen or length > self._maxlen:
             self.length_error(obj, value)
 
         return super(List, self).validate_elements(obj, value)
 
 
 class Set(Container):
     """An instance of a Python set."""
     klass = set
 
 class Tuple(Container):
     """An instance of a Python tuple."""
     klass = tuple
 
     def __init__(self, *traits, **metadata):
         """Tuple(*traits, default_value=None, allow_none=True, **medatata)
 
         Create a tuple from a list, set, or tuple.
 
         Create a fixed-type tuple with Traits:
 
         ``t = Tuple(Int, Str, CStr)``
 
         would be length 3, with Int,Str,CStr for each element.
 
         If only one arg is given and it is not a Trait, it is taken as
         default_value:
 
         ``t = Tuple((1,2,3))``
 
         Otherwise, ``default_value`` *must* be specified by keyword.
 
         Parameters
         ----------
 
         *traits : TraitTypes [ optional ]
             the tsype for restricting the contents of the Tuple.  If unspecified,
             types are not checked. If specified, then each positional argument
             corresponds to an element of the tuple.  Tuples defined with traits
             are of fixed length.
 
         default_value : SequenceType [ optional ]
             The default value for the Tuple.  Must be list/tuple/set, and
             will be cast to a tuple. If `traits` are specified, the
             `default_value` must conform to the shape and type they specify.
 
         allow_none : Bool [ default True ]
             Whether to allow the value to be None
 
         **metadata : any
             further keys for extensions to the Trait (e.g. config)
 
         """
         default_value = metadata.pop('default_value', None)
         allow_none = metadata.pop('allow_none', True)
 
         # allow Tuple((values,)):
         if len(traits) == 1 and default_value is None and not is_trait(traits[0]):
             default_value = traits[0]
             traits = ()
 
         if default_value is None:
             args = ()
         elif isinstance(default_value, self._valid_defaults):
             args = (default_value,)
         else:
             raise TypeError('default value of %s was %s' %(self.__class__.__name__, default_value))
 
         self._traits = []
         for trait in traits:
             t = trait() if isinstance(trait, type) else trait
             t.name = 'element'
             self._traits.append(t)
 
         if self._traits and default_value is None:
             # don't allow default to be an empty container if length is specified
             args = None
         super(Container,self).__init__(klass=self.klass, args=args,
                                   allow_none=allow_none, **metadata)
 
     def validate_elements(self, obj, value):
         if not self._traits:
             # nothing to validate
             return value
         if len(value) != len(self._traits):
             e = "The '%s' trait of %s instance requires %i elements, but a value of %s was specified." \
                 % (self.name, class_of(obj), len(self._traits), repr_type(value))
             raise TraitError(e)
 
         validated = []
         for t,v in zip(self._traits, value):
             try:
                 v = t.validate(obj, v)
             except TraitError:
                 self.element_error(obj, v, t)
             else:
                 validated.append(v)
         return tuple(validated)
 
 
 class Dict(Instance):
     """An instance of a Python dict."""
 
     def __init__(self, default_value=None, allow_none=True, **metadata):
         """Create a dict trait type from a dict.
 
         The default value is created by doing ``dict(default_value)``,
         which creates a copy of the ``default_value``.
         """
         if default_value is None:
             args = ((),)
         elif isinstance(default_value, dict):
             args = (default_value,)
         elif isinstance(default_value, SequenceTypes):
             args = (default_value,)
         else:
             raise TypeError('default value of Dict was %s' % default_value)
 
         super(Dict,self).__init__(klass=dict, args=args,
                                   allow_none=allow_none, **metadata)
 
 class TCPAddress(TraitType):
     """A trait for an (ip, port) tuple.
 
     This allows for both IPv4 IP addresses as well as hostnames.
     """
 
     default_value = ('127.0.0.1', 0)
     info_text = 'an (ip, port) tuple'
 
     def validate(self, obj, value):
         if isinstance(value, tuple):
             if len(value) == 2:
                 if isinstance(value[0], py3compat.string_types) and isinstance(value[1], int):
                     port = value[1]
                     if port >= 0 and port <= 65535:
                         return value
         self.error(obj, value)
 
 class CRegExp(TraitType):
     """A casting compiled regular expression trait.
 
     Accepts both strings and compiled regular expressions. The resulting
     attribute will be a compiled regular expression."""
 
     info_text = 'a regular expression'
 
     def validate(self, obj, value):
         try:
             return re.compile(value)
         except:
             self.error(obj, value)