IPython/core/interactiveshell.py

# -*- coding: utf-8 -*-
"""Main IPython class."""

#-----------------------------------------------------------------------------
#  Copyright (C) 2001 Janko Hauser <[e-mail]>
#  Copyright (C) 2001-2007 Fernando Perez. <[e-mail]>
#  Copyright (C) 2008-2010  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 with_statement
from __future__ import absolute_import

import __builtin__
import abc
import codeop
import exceptions
import new
import os
import re
import string
import sys
import tempfile
from contextlib import nested

from IPython.core import debugger, oinspect
from IPython.core import history as ipcorehist
from IPython.core import prefilter
from IPython.core import shadowns
from IPython.core import ultratb
from IPython.core.alias import AliasManager
from IPython.core.builtin_trap import BuiltinTrap
from IPython.config.configurable import Configurable
from IPython.core.display_trap import DisplayTrap
from IPython.core.error import UsageError
from IPython.core.extensions import ExtensionManager
from IPython.core.fakemodule import FakeModule, init_fakemod_dict
from IPython.core.inputlist import InputList
from IPython.core.logger import Logger
from IPython.core.magic import Magic
from IPython.core.plugin import PluginManager
from IPython.core.prefilter import PrefilterManager
from IPython.core.displayhook import DisplayHook
import IPython.core.hooks
from IPython.external.Itpl import ItplNS
from IPython.utils import PyColorize
from IPython.utils import pickleshare
from IPython.utils.doctestreload import doctest_reload
from IPython.utils.ipstruct import Struct
import IPython.utils.io
from IPython.utils.io import ask_yes_no
from IPython.utils.path import get_home_dir, get_ipython_dir, HomeDirError
from IPython.utils.process import getoutput, getoutputerror
from IPython.utils.strdispatch import StrDispatch
from IPython.utils.syspathcontext import prepended_to_syspath
from IPython.utils.text import num_ini_spaces
from IPython.utils.warn import warn, error, fatal
from IPython.utils.traitlets import (
    Int, Str, CBool, CaselessStrEnum, Enum, List, Unicode, Instance, Type
)

# from IPython.utils import growl
# growl.start("IPython")

#-----------------------------------------------------------------------------
# Globals
#-----------------------------------------------------------------------------

# compiled regexps for autoindent management
dedent_re = re.compile(r'^\s+raise|^\s+return|^\s+pass')

#-----------------------------------------------------------------------------
# Utilities
#-----------------------------------------------------------------------------

# store the builtin raw_input globally, and use this always, in case user code
# overwrites it (like wx.py.PyShell does)
raw_input_original = raw_input

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


def no_op(*a, **kw): pass

class SpaceInInput(exceptions.Exception): pass

class Bunch: pass


def get_default_colors():
    if sys.platform=='darwin':
        return "LightBG"
    elif os.name=='nt':
        return 'Linux'
    else:
        return 'Linux'


class SeparateStr(Str):
    """A Str subclass to validate separate_in, separate_out, etc.

    This is a Str based trait that converts '0'->'' and '\\n'->'\n'.
    """

    def validate(self, obj, value):
        if value == '0': value = ''
        value = value.replace('\\n','\n')
        return super(SeparateStr, self).validate(obj, value)

class MultipleInstanceError(Exception):
    pass


#-----------------------------------------------------------------------------
# Main IPython class
#-----------------------------------------------------------------------------


class InteractiveShell(Configurable, Magic):
    """An enhanced, interactive shell for Python."""

    _instance = None
    autocall = Enum((0,1,2), default_value=1, config=True)
    # 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)
    automagic = CBool(True, config=True)
    cache_size = Int(1000, config=True)
    color_info = CBool(True, config=True)
    colors = CaselessStrEnum(('NoColor','LightBG','Linux'), 
                             default_value=get_default_colors(), config=True)
    debug = CBool(False, config=True)
    deep_reload = CBool(False, config=True)
    displayhook_class = Type(DisplayHook)
    filename = Str("<ipython console>")
    ipython_dir= Unicode('', config=True) # Set to get_ipython_dir() in __init__
    logstart = CBool(False, config=True)
    logfile = Str('', config=True)
    logappend = Str('', config=True)
    object_info_string_level = Enum((0,1,2), default_value=0,
                                    config=True)
    pdb = CBool(False, config=True)
    pprint = CBool(True, config=True)
    profile = Str('', config=True)
    prompt_in1 = Str('In [\\#]: ', config=True)
    prompt_in2 = Str('   .\\D.: ', config=True)
    prompt_out = Str('Out[\\#]: ', config=True)
    prompts_pad_left = CBool(True, config=True)
    quiet = CBool(False, 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_merge_completions = CBool(True, config=True)
    readline_omit__names = Enum((0,1,2), default_value=0, config=True)
    readline_remove_delims = Str('-/~', config=True)
    readline_parse_and_bind = List([
            'tab: complete',
            '"\C-l": clear-screen',
            'set show-all-if-ambiguous on',
            '"\C-o": tab-insert',
            '"\M-i": "    "',
            '"\M-o": "\d\d\d\d"',
            '"\M-I": "\d\d\d\d"',
            '"\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)

    # TODO: this part of prompt management should be moved to the frontends.
    # Use custom TraitTypes that convert '0'->'' and '\\n'->'\n'
    separate_in = SeparateStr('\n', config=True)
    separate_out = SeparateStr('\n', config=True)
    separate_out2 = SeparateStr('\n', config=True)
    system_header = Str('IPython system call: ', config=True)
    system_verbose = CBool(False, 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')
    plugin_manager = Instance('IPython.core.plugin.PluginManager')
    payload_manager = Instance('IPython.core.paylaod.PayloadManager')

    def __init__(self, config=None, ipython_dir=None,
                 user_ns=None, user_global_ns=None,
                 custom_exceptions=((),None)):

        # This is where traits with a config_key argument are updated
        # from the values on config.
        super(InteractiveShell, self).__init__(config=config)

        # These are relatively independent and stateless
        self.init_ipython_dir(ipython_dir)
        self.init_instance_attrs()

        # Create namespaces (user_ns, user_global_ns, etc.)
        self.init_create_namespaces(user_ns, user_global_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()

        self.init_history()
        self.init_encoding()
        self.init_prefilter()

        Magic.__init__(self, self)

        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_alias()
        self.init_builtins()

        # pre_config_initialization
        self.init_shadow_hist()

        # The next section should contain averything that was in ipmaker.
        self.init_logstart()

        # 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()
        # 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_displayhook()
        self.init_reload_doctest()
        self.init_magics()
        self.init_pdb()
        self.init_extension_manager()
        self.init_plugin_manager()
        self.init_payload()
        self.hooks.late_startup_hook()

    @classmethod
    def instance(cls, *args, **kwargs):
        """Returns a global InteractiveShell instance."""
        if cls._instance is None:
            inst = cls(*args, **kwargs)
            # Now make sure that the instance will also be returned by
            # the subclasses instance attribute.
            for subclass in cls.mro():
                if issubclass(cls, subclass) and issubclass(subclass, InteractiveShell):
                    subclass._instance = inst
                else:
                    break
        if isinstance(cls._instance, cls):
            return cls._instance
        else:
            raise MultipleInstanceError(
                'Multiple incompatible subclass instances of '
                'InteractiveShell are being created.'
            )

    @classmethod
    def initialized(cls):
        return hasattr(cls, "_instance")

    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 = 0777)

    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 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
            self.config.Global.ipython_dir = self.ipython_dir
            return

        if hasattr(self.config.Global, 'ipython_dir'):
            self.ipython_dir = self.config.Global.ipython_dir
        else:
            self.ipython_dir = get_ipython_dir()

        # All children can just read this
        self.config.Global.ipython_dir = self.ipython_dir

    def init_instance_attrs(self):
        self.more = False

        # command compiler
        self.compile = codeop.CommandCompiler()

        # User input buffer
        self.buffer = []

        # 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()

        # Object variable to store code object waiting execution.  This is
        # used mainly by the multithreaded shells, but it can come in handy in
        # other situations.  No need to use a Queue here, since it's a single
        # item which gets cleared once run.
        self.code_to_run = None

        # 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.getcwd()

        # Indentation management
        self.indent_current_nsp = 0

    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
        try:
            self.home_dir = get_home_dir()
        except HomeDirError, msg:
            fatal(msg)

        self.dir_stack = []

    def init_logger(self):
        self.logger = Logger(self, logfname='ipython_log.py', logmode='rotate')
        # local shortcut, this is used a LOT
        self.log = self.logger.log

    def init_logstart(self):
        if self.logappend:
            self.magic_logstart(self.logappend + ' append')
        elif self.logfile:
            self.magic_logstart(self.logfile)
        elif self.logstart:
            self.magic_logstart()

    def init_builtins(self):
        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):
        import IPython.utils.io
        if sys.platform == 'win32' and self.has_readline:
            Term = IPython.utils.io.IOTerm(
                cout=self.readline._outputfile,cerr=self.readline._outputfile
            )
        else:
            Term = IPython.utils.io.IOTerm()
        IPython.utils.io.Term = Term

    def init_prompts(self):
        # TODO: This is a pass for now because the prompts are managed inside
        # the DisplayHook. Once there is a separate prompt manager, this 
        # will initialize that object and all prompt related information.
        pass

    def init_displayhook(self):
        # Initialize displayhook, set in/out prompts and printing system
        self.displayhook = self.displayhook_class(
            shell=self,
            cache_size=self.cache_size,
            input_sep = self.separate_in,
            output_sep = self.separate_out,
            output_sep2 = self.separate_out2,
            ps1 = self.prompt_in1,
            ps2 = self.prompt_in2,
            ps_out = self.prompt_out,
            pad_left = self.prompts_pad_left
        )
        # This is a context manager that installs/revmoes the displayhook at
        # the appropriate time.
        self.display_trap = DisplayTrap(hook=self.displayhook)

    def init_reload_doctest(self):
        # Do a proper resetting of doctest, including the necessary displayhook
        # monkeypatching
        try:
            doctest_reload()
        except ImportError:
            warn("doctest module does not exist.")

    #-------------------------------------------------------------------------
    # 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_ns 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
        try:
            self._orig_sys_modules_main_name = self.user_ns['__name__']
        except KeyError:
            pass

    def restore_sys_module_state(self):
        """Restore the state of the sys module."""
        try:
            for k, v in self._orig_sys_module_state.items():
                setattr(sys, k, v)
        except AttributeError:
            pass
        try:
            delattr(sys, 'ipcompleter')
        except AttributeError:
            pass
        # Reset what what done in self.init_sys_modules
        try:
            sys.modules[self.user_ns['__name__']] = self._orig_sys_modules_main_name
        except (AttributeError, KeyError):
            pass

    #-------------------------------------------------------------------------
    # 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 = new.instancemethod(hook,self,self.__class__)

        # 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)

    #-------------------------------------------------------------------------
    # Things related to the "main" module
    #-------------------------------------------------------------------------

    def new_main_mod(self,ns=None):
        """Return a new 'main' module object for user code execution.
        """
        main_mod = self._user_main_module
        init_fakemod_dict(main_mod,ns)
        return main_mod

    def cache_main_mod(self,ns,fname):
        """Cache a main module's namespace.

        When scripts are executed via %run, we must keep a reference to the
        namespace of their __main__ module (a FakeModule instance) around so
        that Python doesn't clear it, rendering objects defined therein
        useless.

        This method keeps said reference in a private dict, keyed by the
        absolute path of the module object (which corresponds to the script
        path).  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.

        Note: we can not allow the actual FakeModule instances to be deleted,
        because of how Python tears down modules (it hard-sets all their
        references to None without regard for reference counts).  This method
        must therefore make a *copy* of the given namespace, to allow the
        original module's __dict__ to be cleared and reused.

        
        Parameters
        ----------
          ns : a namespace (a dict, typically)

          fname : str
            Filename associated with the namespace.

        Examples
        --------

        In [10]: import IPython

        In [11]: _ip.cache_main_mod(IPython.__dict__,IPython.__file__)

        In [12]: IPython.__file__ in _ip._main_ns_cache
        Out[12]: True
        """
        self._main_ns_cache[os.path.abspath(fname)] = ns.copy()

    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]: _ip.cache_main_mod(IPython.__dict__,IPython.__file__)

        In [17]: len(_ip._main_ns_cache) > 0
        Out[17]: True

        In [18]: _ip.clear_main_mod_cache()

        In [19]: len(_ip._main_ns_cache) == 0
        Out[19]: True
        """
        self._main_ns_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)
        self.history_saving_wrapper(pm)()

    #-------------------------------------------------------------------------
    # Things related to IPython's various namespaces
    #-------------------------------------------------------------------------

    def init_create_namespaces(self, user_ns=None, user_global_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 properly built dicts as needed by the rest of
        # the code, and can also be used by extension writers to generate
        # properly initialized namespaces.
        user_ns, user_global_ns = self.make_user_namespaces(user_ns, user_global_ns)

        # Assign namespaces
        # This is the namespace where all normal user variables live
        self.user_ns = user_ns
        self.user_global_ns = user_global_ns

        # An auxiliary namespace that checks what parts of the user_ns were
        # loaded at startup, so we can list later only variables defined in
        # actual interactive use.  Since it is always a subset of user_ns, it
        # doesn't need to be separately tracked in the ns_table.
        self.user_ns_hidden = {}

        # A namespace to keep track of internal data structures to prevent
        # them from cluttering user-visible stuff.  Will be updated later
        self.internal_ns = {}

        # 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_ns_cache = {}
        # And this is the single instance of FakeModule whose __dict__ we keep
        # copying and clearing for reuse on each %run
        self._user_main_module = FakeModule()

        # A table holding all the namespaces IPython deals with, so that
        # introspection facilities can search easily.
        self.ns_table = {'user':user_ns,
                         'user_global':user_global_ns,
                         'internal':self.internal_ns,
                         'builtin':__builtin__.__dict__
                         }

        # Similarly, track all namespaces where references can be held and that
        # we can safely clear (so it can NOT include builtin).  This one can be
        # a simple list.
        self.ns_refs_table = [ user_ns, user_global_ns, self.user_ns_hidden,
                               self.internal_ns, self._main_ns_cache ]

    def make_user_namespaces(self, user_ns=None, user_global_ns=None):
        """Return a valid local and global user interactive namespaces.

        This builds a dict with the minimal information needed to operate as a
        valid IPython user namespace, which you can pass to the various
        embedding classes in ipython. The default implementation returns the
        same dict for both the locals and the globals to allow functions to
        refer to variables in the namespace. Customized implementations can
        return different dicts. The locals dictionary can actually be anything
        following the basic mapping protocol of a dict, but the globals dict
        must be a true dict, not even a subclass. It is recommended that any
        custom object for the locals namespace synchronize with the globals
        dict somehow.

        Raises TypeError if the provided globals namespace is not a true dict.

        Parameters
        ----------
        user_ns : dict-like, optional
            The current user namespace. The items in this namespace should
            be included in the output. If None, an appropriate blank
            namespace should be created.
        user_global_ns : dict, optional
            The current user global namespace. The items in this namespace
            should be included in the output. If None, an appropriate
            blank namespace should be created.

        Returns
        -------
            A pair of dictionary-like object to be used as the local namespace
            of the interpreter and a dict to be used as the global namespace.
        """


        # 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

        if user_ns is None:
            # Set __name__ to __main__ to better match the behavior of the
            # normal interpreter.
            user_ns = {'__name__'     :'__main__',
                       '__builtin__' : __builtin__,
                       '__builtins__' : __builtin__,
                      }
        else:
            user_ns.setdefault('__name__','__main__')
            user_ns.setdefault('__builtin__',__builtin__)
            user_ns.setdefault('__builtins__',__builtin__)

        if user_global_ns is None:
            user_global_ns = user_ns
        if type(user_global_ns) is not dict:
            raise TypeError("user_global_ns must be a true dict; got %r"
                % type(user_global_ns))

        return user_ns, user_global_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.

        try:
            main_name = self.user_ns['__name__']
        except KeyError:
            raise KeyError('user_ns dictionary MUST have a "__name__" key')
        else:
            sys.modules[main_name] = FakeModule(self.user_ns)

    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(__builtin__ = __builtin__)
        
        # 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.input_hist
        ns['_oh'] = self.output_hist
        ns['_dh'] = self.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.input_hist
        ns['Out'] = self.output_hist

        # Store myself as the public api!!!
        ns['get_ipython'] = self.get_ipython

        # 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)


    def reset(self):
        """Clear all internal namespaces.

        Note that this is much more aggressive than %reset, since it clears
        fully all namespaces, as well as all input/output lists.
        """
        for ns in self.ns_refs_table:
            ns.clear()

        self.alias_manager.clear_aliases()

        # Clear input and output histories
        self.input_hist[:] = []
        self.input_hist_raw[:] = []
        self.output_hist.clear()

        # Restore the user namespaces to minimal usability
        self.init_user_ns()

        # Restore the default and user aliases
        self.alias_manager.init_aliases()

    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.ns_refs_table:
                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, (basestring, list, tuple)):
            if isinstance(variables, basestring):
                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
        config_ns = self.user_ns_hidden
        if interactive:
            for name, val in vdict.iteritems():
                config_ns.pop(name, None)
        else:
            for name,val in vdict.iteritems():
                config_ns[name] = val

    #-------------------------------------------------------------------------
    # Things related to history management
    #-------------------------------------------------------------------------

    def init_history(self):
        # List of input with multi-line handling.
        self.input_hist = InputList()
        # This one will hold the 'raw' input history, without any
        # pre-processing.  This will allow users to retrieve the input just as
        # it was exactly typed in by the user, with %hist -r.
        self.input_hist_raw = InputList()

        # list of visited directories
        try:
            self.dir_hist = [os.getcwd()]
        except OSError:
            self.dir_hist = []

        # dict of output history
        self.output_hist = {}

        # Now the history file
        if self.profile:
            histfname = 'history-%s' % self.profile
        else:
            histfname = 'history'
        self.histfile = os.path.join(self.ipython_dir, histfname)

        # Fill the history zero entry, user counter starts at 1
        self.input_hist.append('\n')
        self.input_hist_raw.append('\n')

    def init_shadow_hist(self):
        try:
            self.db = pickleshare.PickleShareDB(self.ipython_dir + "/db")
        except exceptions.UnicodeDecodeError:
            print "Your ipython_dir can't be decoded to unicode!"
            print "Please set HOME environment variable to something that"
            print r"only has ASCII characters, e.g. c:\home"
            print "Now it is", self.ipython_dir
            sys.exit()
        self.shadowhist = ipcorehist.ShadowHist(self.db)

    def savehist(self):
        """Save input history to a file (via readline library)."""

        try:
            self.readline.write_history_file(self.histfile)
        except:
            print 'Unable to save IPython command history to file: ' + \
                  `self.histfile`

    def reloadhist(self):
        """Reload the input history from disk file."""

        try:
            self.readline.clear_history()
            self.readline.read_history_file(self.shell.histfile)
        except AttributeError:
            pass

    def history_saving_wrapper(self, func):
        """ Wrap func for readline history saving

        Convert func into callable that saves & restores
        history around the call """

        if self.has_readline:
            from IPython.utils import rlineimpl as readline
        else:
            return func

        def wrapper():
            self.savehist()
            try:
                func()
            finally:
                readline.read_history_file(self.histfile)
        return wrapper

    def get_history(self, index=None, raw=False, output=True):
        """Get the history list.

        Get the input and output history.

        Parameters
        ----------
        index : n or (n1, n2) or None
            If n, then the last entries. If a tuple, then all in
            range(n1, n2). If None, then all entries. Raises IndexError if
            the format of index is incorrect.
        raw : bool
            If True, return the raw input.
        output : bool
            If True, then return the output as well.

        Returns
        -------
        If output is True, then return a dict of tuples, keyed by the prompt
        numbers and with values of (input, output). If output is False, then
        a dict, keyed by the prompt number with the values of input. Raises
        IndexError if no history is found.
        """
        if raw:
            input_hist = self.input_hist_raw
        else:
            input_hist = self.input_hist
        if output:
            output_hist = self.user_ns['Out']
        n = len(input_hist)
        if index is None:
            start=0; stop=n
        elif isinstance(index, int):
            start=n-index; stop=n
        elif isinstance(index, tuple) and len(index) == 2:
            start=index[0]; stop=index[1]
        else:
            raise IndexError('Not a valid index for the input history: %r' % index)
        hist = {}
        for i in range(start, stop):
            if output:
                hist[i] = (input_hist[i], output_hist.get(i))
            else:
                hist[i] = input_hist[i]
        if len(hist)==0:
            raise IndexError('No history for range of indices: %r' % index)
        return hist

    #-------------------------------------------------------------------------
    # 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)

        # 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
        runcode() method.

        Inputs:

          - exc_tuple: a *tuple* of valid exceptions to call the defined
          handler for.  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: this must be defined as a function with the following
          basic interface: def my_handler(self,etype,value,tb).

          This will be made into an instance method (via new.instancemethod)
          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.

        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):
            print '*** Simple custom exception handler ***'
            print 'Exception type :',etype
            print 'Exception value:',value
            print 'Traceback      :',tb
            print 'Source code    :','\n'.join(self.buffer)

        if handler is None: handler = dummy_handler

        self.CustomTB = new.instancemethod(handler,self,self.__class__)
        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 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:
            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
                else:
                    self.write('No traceback available to show.\n')
                    return
    
            if etype is SyntaxError:
                # Though this won't be called by syntax errors in the input
                # line, there may be SyntaxError cases whith imported code.
                self.showsyntaxerror(filename)
            elif etype is UsageError:
                print "UsageError:", value
            else:
                # 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
    
                if etype in self.custom_exceptions:
                    self.CustomTB(etype,value,tb)
                else:
                    if exception_only:
                        m = ('An exception has occurred, use %tb to see the '
                             'full traceback.')
                        print m
                        self.InteractiveTB.show_exception_only(etype, value)
                    else:
                        self.InteractiveTB(etype,value,tb,tb_offset=tb_offset)
                        if self.InteractiveTB.call_pdb:
                            # pdb mucks up readline, fix it back
                            self.set_completer()
                        
        except KeyboardInterrupt:
            self.write("\nKeyboardInterrupt\n")        
        

    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 = sys.exc_info()

        # See note about these variables in showtraceback() above
        sys.last_type = etype
        sys.last_value = value
        sys.last_traceback = last_traceback
        
        if filename and etype is SyntaxError:
            # Work hard to stuff the correct filename in the exception
            try:
                msg, (dummy_filename, lineno, offset, line) = value
            except:
                # Not the format we expect; leave it alone
                pass
            else:
                # Stuff in the right filename
                try:
                    # Assume SyntaxError is a class exception
                    value = SyntaxError(msg, (filename, lineno, offset, line))
                except:
                    # If that failed, assume SyntaxError is a string
                    value = msg, (filename, lineno, offset, line)
        self.SyntaxTB(etype,value,[])

    #-------------------------------------------------------------------------
    # Things related to tab completion
    #-------------------------------------------------------------------------

    def complete(self, text):
        """Return a sorted list of all possible completions on text.

        Inputs:

          - text: a string of text to be completed on.

        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 [7]: x = 'hello'

        In [8]: x
        Out[8]: 'hello'

        In [9]: print x
        hello

        In [10]: _ip.complete('x.l')
        Out[10]: ['x.ljust', 'x.lower', 'x.lstrip']
        """

        # Inject names into __builtin__ so we can complete on the added names.
        with self.builtin_trap:
            complete = self.Completer.complete
            state = 0
            # use a dict so we get unique keys, since ipyhton's multiple
            # completers can return duplicates.  When we make 2.4 a requirement,
            # start using sets instead, which are faster.
            comps = {}
            while True:
                newcomp = complete(text,state,line_buffer=text)
                if newcomp is None:
                    break
                comps[newcomp] = 1
                state += 1
            outcomps = comps.keys()
            outcomps.sort()
            #print "T:",text,"OC:",outcomps  # dbg
            #print "vars:",self.user_ns.keys()
            return outcomps

    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 = new.instancemethod(completer,self.Completer,
                                     self.Completer.__class__)
        self.Completer.matchers.insert(pos,newcomp)

    def set_completer(self):
        """Reset readline's completer to be our own."""
        self.readline.set_completer(self.Completer.complete)

    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 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.savehist = no_op
            self.reloadhist = no_op
            self.set_completer = no_op
            self.set_custom_completer = no_op
            self.set_completer_frame = no_op
            warn('Readline services not available or not loaded.')
        else:
            self.has_readline = True
            self.readline = readline
            sys.modules['readline'] = readline
            import atexit
            from IPython.core.completer import IPCompleter
            self.Completer = IPCompleter(self,
                                         self.user_ns,
                                         self.user_global_ns,
                                         self.readline_omit__names,
                                         self.alias_manager.alias_table)
            sdisp = self.strdispatchers.get('complete_command', StrDispatch())
            self.strdispatchers['complete_command'] = sdisp
            self.Completer.custom_completers = sdisp
            # Platform-specific configuration
            if os.name == 'nt':
                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:
                home_dir = get_home_dir()
                if home_dir is not None:
                    inputrc_name = '.inputrc'
                    if readline.uses_libedit:
                        inputrc_name = '.editrc'
                    inputrc_name = os.path.join(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)
            
            # save this in sys so embedded copies can restore it properly
            sys.ipcompleter = self.Completer.complete
            self.set_completer()

            # 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().encode("ascii", "ignore")
            delims = delims.translate(string._idmap,
                                      self.readline_remove_delims)
            readline.set_completer_delims(delims)
            # otherwise we end up with a monster history after a while:
            readline.set_history_length(1000)
            try:
                #print '*** Reading readline history'  # dbg
                readline.read_history_file(self.histfile)
            except IOError:
                pass  # It doesn't exist yet.

            atexit.register(self.atexit_operations)
            del atexit

        # Configure auto-indent for all platforms
        self.set_autoindent(self.autoindent)

    def set_next_input(self, s):
        """ Sets the 'default' input string for the next command line.
        
        Requires readline.
        
        Example:
        
        [D:\ipython]|1> _ip.set_next_input("Hello Word")
        [D:\ipython]|2> Hello Word_  # cursor is here        
        """

        self.rl_next_input = 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.indent_current_nsp * ' '

    #-------------------------------------------------------------------------
    # Things related to magics
    #-------------------------------------------------------------------------

    def init_magics(self):
        # 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(self.colors)
        # History was moved to a separate module
        from . import history
        history.init_ipython(self)

    def magic(self,arg_s):
        """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.
        """
        args = arg_s.split(' ',1)
        magic_name = args[0]
        magic_name = magic_name.lstrip(prefilter.ESC_MAGIC)

        try:
            magic_args = args[1]
        except IndexError:
            magic_args = ''
        fn = getattr(self,'magic_'+magic_name,None)
        if fn is None:
            error("Magic function `%s` not found." % magic_name)
        else:
            magic_args = self.var_expand(magic_args,1)
            with nested(self.builtin_trap,):
                result = fn(magic_args)
                return result

    def define_magic(self, magicname, func):
        """Expose own function as magic function for ipython 
    
        def foo_impl(self,parameter_s=''):
            'My very own magic!. (Use docstrings, IPython reads them).'
            print 'Magic function. Passed parameter is between < >:'
            print '<%s>' % parameter_s
            print 'The self object is:',self
    
        self.define_magic('foo',foo_impl)
        """
        
        import new
        im = new.instancemethod(func,self, self.__class__)
        old = getattr(self, "magic_" + magicname, None)
        setattr(self, "magic_" + magicname, im)
        return old

    #-------------------------------------------------------------------------
    # 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, basestring):
            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(self, cmd):
        """Make a system call, using IPython."""
        return self.hooks.shell_hook(self.var_expand(cmd, depth=2))

    #-------------------------------------------------------------------------
    # Things related to aliases
    #-------------------------------------------------------------------------

    def init_alias(self):
        self.alias_manager = AliasManager(shell=self, config=self.config)
        self.ns_table['alias'] = self.alias_manager.alias_table,

    #-------------------------------------------------------------------------
    # Things related to extensions and plugins
    #-------------------------------------------------------------------------

    def init_extension_manager(self):
        self.extension_manager = ExtensionManager(shell=self, config=self.config)

    def init_plugin_manager(self):
        self.plugin_manager = PluginManager(config=self.config)

    #-------------------------------------------------------------------------
    # Things related to payloads
    #-------------------------------------------------------------------------

    def init_payload(self):
        self.payload_manager = PayloadManager(config=self.config)

    #-------------------------------------------------------------------------
    # Things related to the prefilter
    #-------------------------------------------------------------------------

    def init_prefilter(self):
        self.prefilter_manager = PrefilterManager(shell=self, config=self.config)
        # 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

    #-------------------------------------------------------------------------
    # Things related to the running of code
    #-------------------------------------------------------------------------

    def ex(self, cmd):
        """Execute a normal python statement in user namespace."""
        with nested(self.builtin_trap,):
            exec cmd in self.user_global_ns, self.user_ns

    def ev(self, expr):
        """Evaluate python expression expr in user namespace.

        Returns the result of evaluation
        """
        with nested(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).
        """
        kw.setdefault('exit_ignore', False)

        fname = os.path.abspath(os.path.expanduser(fname))

        # Make sure we have a .py file
        if not fname.endswith('.py'):
            warn('File must end with .py to be run using execfile: <%s>' % 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:
                execfile(fname,*where)
            except SystemExit, 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 status.code not in (0, None) and not kw['exit_ignore']:
                    self.showtraceback(exception_only=True)
            except:
                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 have a .py file
        if not fname.endswith('.ipy'):
            warn('File must end with .py to be run using execfile: <%s>' % 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:
                    script = thefile.read()
                    # self.runlines currently captures all exceptions
                    # raise in user code.  It would be nice if there were
                    # versions of runlines, execfile that did raise, so
                    # we could catch the errors.
                    self.runlines(script, clean=True)
            except:
                self.showtraceback()
                warn('Unknown failure executing file: <%s>' % fname)

    def runlines(self, lines, clean=False):
        """Run a string of one or more lines of source.

        This method is capable of running a string containing multiple source
        lines, as if they had been entered at the IPython prompt.  Since it
        exposes IPython's processing machinery, the given strings can contain
        magic calls (%magic), special shell access (!cmd), etc.
        """

        if isinstance(lines, (list, tuple)):
            lines = '\n'.join(lines)

        if clean:
            lines = self._cleanup_ipy_script(lines)

        # We must start with a clean buffer, in case this is run from an
        # interactive IPython session (via a magic, for example).
        self.resetbuffer()
        lines = lines.splitlines()
        more = 0

        with nested(self.builtin_trap, self.display_trap):
            for line in lines:
                # skip blank lines so we don't mess up the prompt counter, but do
                # NOT skip even a blank line if we are in a code block (more is
                # true)
            
                if line or more:
                    # push to raw history, so hist line numbers stay in sync
                    self.input_hist_raw.append("# " + line + "\n")
                    prefiltered = self.prefilter_manager.prefilter_lines(line,more)
                    more = self.push_line(prefiltered)
                    # IPython's runsource returns None if there was an error
                    # compiling the code.  This allows us to stop processing right
                    # away, so the user gets the error message at the right place.
                    if more is None:
                        break
                else:
                    self.input_hist_raw.append("\n")
            # final newline in case the input didn't have it, so that the code
            # actually does get executed
            if more:
                self.push_line('\n')

    def runsource(self, source, filename='<input>', symbol='single'):
        """Compile and run some source in the interpreter.

        Arguments are as for compile_command().

        One several things can happen:

        1) The input is incorrect; compile_command() raised an
        exception (SyntaxError or OverflowError).  A syntax traceback
        will be printed by calling the showsyntaxerror() method.

        2) The input is incomplete, and more input is required;
        compile_command() returned None.  Nothing happens.

        3) The input is complete; compile_command() returned a code
        object.  The code is executed by calling self.runcode() (which
        also handles run-time exceptions, except for SystemExit).

        The return value is:

          - True in case 2

          - False in the other cases, unless an exception is raised, where
          None is returned instead.  This can be used by external callers to
          know whether to continue feeding input or not.

        The return value can be used to decide whether to use sys.ps1 or
        sys.ps2 to prompt the next line."""

        # if the source code has leading blanks, add 'if 1:\n' to it
        # this allows execution of indented pasted code. It is tempting
        # to add '\n' at the end of source to run commands like ' a=1'
        # directly, but this fails for more complicated scenarios
        source=source.encode(self.stdin_encoding)
        if source[:1] in [' ', '\t']:
            source = 'if 1:\n%s' % source

        try:
            code = self.compile(source,filename,symbol)
        except (OverflowError, SyntaxError, ValueError, TypeError, MemoryError):
            # Case 1
            self.showsyntaxerror(filename)
            return None

        if code is None:
            # Case 2
            return True

        # Case 3
        # We store the code object so that threaded shells and
        # custom exception handlers can access all this info if needed.
        # The source corresponding to this can be obtained from the
        # buffer attribute as '\n'.join(self.buffer).
        self.code_to_run = code
        # now actually execute the code object
        if self.runcode(code) == 0:
            return False
        else:
            return None

    def runcode(self,code_obj):
        """Execute a code object.

        When an exception occurs, self.showtraceback() is called to display a
        traceback.

        Return value: a flag indicating whether the code to be run completed
        successfully:

          - 0: successful execution.
          - 1: 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_runcode_hook()
                exec code_obj in self.user_global_ns, self.user_ns
            finally:
                # Reset our crash handler in place
                sys.excepthook = old_excepthook
        except SystemExit:
            self.resetbuffer()
            self.showtraceback(exception_only=True)
            warn("To exit: use any of 'exit', 'quit', %Exit 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
            if softspace(sys.stdout, 0):
                print
        # Flush out code object which has been run (and source)
        self.code_to_run = None
        return outflag
        
    def push_line(self, line):
        """Push a line to the interpreter.

        The line should not have a trailing newline; it may have
        internal newlines.  The line is appended to a buffer and the
        interpreter's runsource() method is called with the
        concatenated contents of the buffer as source.  If this
        indicates that the command was executed or invalid, the buffer
        is reset; otherwise, the command is incomplete, and the buffer
        is left as it was after the line was appended.  The return
        value is 1 if more input is required, 0 if the line was dealt
        with in some way (this is the same as runsource()).
        """

        # autoindent management should be done here, and not in the
        # interactive loop, since that one is only seen by keyboard input.  We
        # need this done correctly even for code run via runlines (which uses
        # push).

        #print 'push line: <%s>' % line  # dbg
        for subline in line.splitlines():
            self._autoindent_update(subline)
        self.buffer.append(line)
        more = self.runsource('\n'.join(self.buffer), self.filename)
        if not more:
            self.resetbuffer()
        return more

    def resetbuffer(self):
        """Reset the input buffer."""
        self.buffer[:] = []

    def _is_secondary_block_start(self, s):
        if not s.endswith(':'):
            return False
        if (s.startswith('elif') or 
            s.startswith('else') or 
            s.startswith('except') or
            s.startswith('finally')):
            return True

    def _cleanup_ipy_script(self, script):
        """Make a script safe for self.runlines()

        Currently, IPython is lines based, with blocks being detected by
        empty lines.  This is a problem for block based scripts that may
        not have empty lines after blocks.  This script adds those empty
        lines to make scripts safe for running in the current line based
        IPython.
        """
        res = []
        lines = script.splitlines()
        level = 0

        for l in lines:
            lstripped = l.lstrip()
            stripped = l.strip()                
            if not stripped:
                continue
            newlevel = len(l) - len(lstripped)                    
            if level > 0 and newlevel == 0 and \
                   not self._is_secondary_block_start(stripped): 
                # add empty line
                res.append('')
            res.append(l)
            level = newlevel

        return '\n'.join(res) + '\n'

    def _autoindent_update(self,line):
        """Keep track of the indent level."""

        #debugx('line')
        #debugx('self.indent_current_nsp')
        if self.autoindent:
            if line:
                inisp = num_ini_spaces(line)
                if inisp < self.indent_current_nsp:
                    self.indent_current_nsp = inisp

                if line[-1] == ':':
                    self.indent_current_nsp += 4
                elif dedent_re.match(line):
                    self.indent_current_nsp -= 4
            else:
                self.indent_current_nsp = 0

    #-------------------------------------------------------------------------
    # Things related to GUI support and pylab
    #-------------------------------------------------------------------------

    def enable_pylab(self, gui=None):
        raise NotImplementedError('Implement enable_pylab in a subclass')

    #-------------------------------------------------------------------------
    # Utilities
    #-------------------------------------------------------------------------

    def getoutput(self, cmd):
        return getoutput(self.var_expand(cmd,depth=2),
                         header=self.system_header,
                         verbose=self.system_verbose)

    def getoutputerror(self, cmd):
        return getoutputerror(self.var_expand(cmd,depth=2),
                              header=self.system_header,
                              verbose=self.system_verbose)

    def var_expand(self,cmd,depth=0):
        """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.
        """

        return str(ItplNS(cmd,
                          self.user_ns,  # globals
                          # Skip our own frame in searching for locals:
                          sys._getframe(depth+1).f_locals # locals
                          ))

    def mktempfile(self,data=None):
        """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','ipython_edit_')
        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"""
        IPython.utils.io.Term.cout.write(data)

    # TODO:  This should be removed when Term is refactored.
    def write_err(self,data):
        """Write a string to the default error output"""
        IPython.utils.io.Term.cerr.write(data)

    def ask_yes_no(self,prompt,default=True):
        if self.quiet:
            return True
        return ask_yes_no(prompt,default)

    #-------------------------------------------------------------------------
    # Things related to IPython exiting
    #-------------------------------------------------------------------------

    def atexit_operations(self):
        """This will be executed at the time of exit.

        Saving of persistent data should be performed here.
        """
        self.savehist()

        # 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()

        # Run user hooks
        self.hooks.shutdown_hook()

    def cleanup(self):
        self.restore_sys_module_state()


class InteractiveShellABC(object):
    """An abstract base class for InteractiveShell."""
    __metaclass__ = abc.ABCMeta

InteractiveShellABC.register(InteractiveShell)