reorder stdlib imports

closes gh-280

IPython/core/formatters.py

@@ -1,557 +1,557 b''
 # -*- coding: utf-8 -*-
 """Display formatters.
 
 
 Authors:
 
 * Robert Kern
 * Brian Granger
 """
 #-----------------------------------------------------------------------------
 # Copyright (c) 2010, 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 sys
 import abc
+import sys
 # We must use StringIO, as cStringIO doesn't handle unicode properly.
 from StringIO import StringIO
 
 # Our own imports
 from IPython.config.configurable import Configurable
 from IPython.external import pretty
 from IPython.utils.traitlets import Bool, Dict, Int, Str, CStr
 
 
 #-----------------------------------------------------------------------------
 # 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)
 
     # A dict of formatter whose keys are format types (MIME types) and whose
     # values are subclasses of BaseFormatter.
     formatters = Dict(config=True)
     def _formatters_default(self):
         """Activate the default formatters."""
         formatter_classes = [
             PlainTextFormatter,
             HTMLFormatter,
             SVGFormatter,
             PNGFormatter,
             LatexFormatter,
             JSONFormatter
         ]
         d = {}
         for cls in formatter_classes:
             f = cls(config=self.config)
             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
         * image/png
         * immage/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 exclue 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 : 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.
         """
         format_dict = {}
 
         # If plain text only is active
         if self.plain_text_only:
             formatter = self.formatters['text/plain']
             try:
                 data = formatter(obj)
             except:
                 # FIXME: log the exception
                 raise
             if data is not None:
                 format_dict['text/plain'] = data
             return format_dict
 
         for format_type, formatter in self.formatters.items():
             if include is not None:
                 if format_type not in include:
                     continue
             if exclude is not None:
                 if format_type in exclude:
                     continue
             try:
                 data = formatter(obj)
             except:
                 # FIXME: log the exception
                 raise
             if data is not None:
                 format_dict[format_type] = data
         return format_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):
     """ 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 = Str('text/plain')
 
     enabled = Bool(True, config=True)
 
     print_method = Str('__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)
                 if hasattr(obj_class, self.print_method):
                     printer = getattr(obj_class, self.print_method)
                     return printer(obj)
                 try:
                     printer = self.singleton_printers[obj_id]
                 except (TypeError, KeyError):
                     pass
                 else:
                     return printer(obj)
                 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)
                 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.external.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.external.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 = Str('text/plain')
 
     # This subclass ignores this attribute as it always need to return
     # something.
     enabled = Bool(True, config=False)
 
     # Look for a __pretty__ methods to use for pretty printing.
     print_method = Str('__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 = Int(79, config=True)
 
     # The newline character.
     newline = Str('\n', config=True)
     
     # format-string for pprinting floats
     float_format = Str('%r')
     # setter for float precision, either int or direct format-string
     float_precision = CStr('', 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.external.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()
             printer = pretty.RepresentationPrinter(stream, self.verbose,
                 self.max_width, 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:`__html__` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
     """
     format_type = Str('text/html')
 
     print_method = Str('__html__')
 
 
 class SVGFormatter(BaseFormatter):
     """An SVG formatter.
 
     To define the callables that compute the SVG representation of your
     objects, define a :meth:`__svg__` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
     """
     format_type = Str('image/svg+xml')
 
     print_method = Str('__svg__')
 
 
 class PNGFormatter(BaseFormatter):
     """A PNG formatter.
 
     To define the callables that compute the PNG representation of your
     objects, define a :meth:`__png__` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this. The raw data should be the base64 encoded raw png data.
     """
     format_type = Str('image/png')
 
     print_method = Str('__png__')
 
 
 class LatexFormatter(BaseFormatter):
     """A LaTeX formatter.
 
     To define the callables that compute the LaTeX representation of your
     objects, define a :meth:`__latex__` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
     """
     format_type = Str('text/latex')
 
     print_method = Str('__latex__')
 
 
 class JSONFormatter(BaseFormatter):
     """A JSON string formatter.
 
     To define the callables that compute the JSON string representation of
     your objects, define a :meth:`__json__` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
     """
     format_type = Str('application/json')
 
     print_method = Str('__json__')
 
 
 FormatterABC.register(BaseFormatter)
 FormatterABC.register(PlainTextFormatter)
 FormatterABC.register(HTMLFormatter)
 FormatterABC.register(SVGFormatter)
 FormatterABC.register(PNGFormatter)
 FormatterABC.register(LatexFormatter)
 FormatterABC.register(JSONFormatter)
 
 
 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
     * image/png
     * immage/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
     )