Merging upstream changes from inputhook and config-refactor.

Some minor changes needed to be made to make sure component queries 
in ipapi worked properly.

docs/examples/lib/gui-gtk.py

@@ -0,0 +1,35 b''
+#!/usr/bin/env python
+"""Simple GTK example to manually test event loop integration.
+
+This is meant to run tests manually in ipython as:
+
+In [5]: %gui gtk
+
+In [6]: %run gui-gtk.py
+"""
+
+
+import pygtk
+pygtk.require('2.0')
+import gtk
+
+
+def hello_world(wigdet, data=None):
+    print "Hello World"
+
+window = gtk.Window(gtk.WINDOW_TOPLEVEL)
+button = gtk.Button("Hello World")
+button.connect("clicked", hello_world, None)
+
+window.add(self.button)
+button.show()
+window.show()
+
+try:
+    from IPython.lib.inputhook import appstart_gtk
+    appstart_gtk()
+except ImportError:
+    gtk.main()
+
+
+

docs/examples/lib/gui-mpl.py

@@ -0,0 +1,54 b''
+"""Test the new %gui command.  Run this in ipython as
+
+In [1]: %gui [backend]
+
+In [2]: %run switchgui [backend]
+
+where the optional backend can be one of:  qt4, gtk, tk, wx.
+
+Because of subtle difference in how Matplotlib handles the different GUI 
+toolkits (in things like draw and show), minor modifications to this script
+have to be made for Tk to get it to work with the 0.99 and below releases
+of Matplotlib.  However, in the future, Matplotlib should be able to have 
+similar logic for all the toolkits, as they are all now using PyOS_InputHook.
+"""
+
+import sys
+import time
+
+from  IPython.lib import inputhook
+
+gui = inputhook.current_gui()
+if gui is None:
+    gui = 'qt4'
+    inputhook.enable_qt4(app=True)
+
+backends = dict(wx='wxagg', qt4='qt4agg', gtk='gtkagg', tk='tkagg')
+
+import matplotlib
+matplotlib.use(backends[gui])
+matplotlib.interactive(True)
+
+import matplotlib
+from matplotlib import pyplot as plt, mlab, pylab
+import numpy as np
+
+from numpy import *
+from matplotlib.pyplot import *
+
+x = np.linspace(0,pi,500)
+
+print "A plot has been created"
+line, = plot(x,sin(2*x))
+inputhook.spin() # This has to be removed for Tk
+
+
+print "Now, we will update the plot..."
+print
+for i in range(1,51):
+    print i, 
+    sys.stdout.flush()
+    line.set_data(x,sin(x*i))
+    plt.title('i=%d' % i)
+    plt.draw()
+    inputhook.spin() # This has to be removed for Tk

docs/examples/lib/gui-qt.py

@@ -0,0 +1,40 b''
+#!/usr/bin/env python
+"""Simple Qt4 example to manually test event loop integration.
+
+This is meant to run tests manually in ipython as:
+
+In [5]: %gui qt
+
+In [6]: %run gui-qt.py
+
+Ref: Modified from http://zetcode.com/tutorials/pyqt4/firstprograms/
+"""
+
+import sys
+from PyQt4 import QtGui, QtCore
+
+class SimpleWindow(QtGui.QWidget):
+    def __init__(self, parent=None):
+        QtGui.QWidget.__init__(self, parent)
+
+        self.setGeometry(300, 300, 200, 80)
+        self.setWindowTitle('Hello World')
+
+        quit = QtGui.QPushButton('Close', self)
+        quit.setGeometry(10, 10, 60, 35)
+
+        self.connect(quit, QtCore.SIGNAL('clicked()'),
+                     self, QtCore.SLOT('close()'))
+
+if __name__ == '__main__':
+    app = QtCore.QCoreApplication.instance()
+    if app is None:
+        app = QtGui.QApplication([])
+
+    sw = SimpleWindow()
+    sw.show()
+
+    try:
+        from IPython import appstart_qt4; appstart_qt4(app)
+    except ImportError:
+        app.exec_()

docs/examples/lib/gui-tk.py

@@ -0,0 +1,32 b''
+#!/usr/bin/env python
+"""Simple Tk example to manually test event loop integration.
+
+This is meant to run tests manually in ipython as:
+
+In [5]: %gui tk
+
+In [6]: %run gui-tk.py
+"""
+
+from Tkinter import *
+
+class MyApp:
+
+    def __init__(self, root):
+        frame = Frame(root)
+        frame.pack()
+
+        self.button = Button(frame, text="Hello", command=self.hello_world)
+        self.button.pack(side=LEFT)
+
+    def hello_world(self):
+        print "Hello World!"
+
+root = Tk()
+
+app = MyApp(root)
+
+try:
+    from IPython import appstart_tk; appstart_tk(root)
+except ImportError:
+    root.mainloop()

docs/examples/lib/gui-wx.py

@@ -0,0 +1,99 b''
+"""A Simple wx example to test IPython's event loop integration.
+
+To run this do:
+
+In [5]: %gui wx
+
+In [6]: %run gui-wx.py
+
+Ref: Modified from wxPython source code wxPython/samples/simple/simple.py
+
+This example can only be run once in a given IPython session.
+"""
+
+import wx
+
+
+class MyFrame(wx.Frame):
+    """
+    This is MyFrame.  It just shows a few controls on a wxPanel,
+    and has a simple menu.
+    """
+    def __init__(self, parent, title):
+        wx.Frame.__init__(self, parent, -1, title,
+                          pos=(150, 150), size=(350, 200))
+
+        # Create the menubar
+        menuBar = wx.MenuBar()
+
+        # and a menu 
+        menu = wx.Menu()
+
+        # add an item to the menu, using \tKeyName automatically
+        # creates an accelerator, the third param is some help text
+        # that will show up in the statusbar
+        menu.Append(wx.ID_EXIT, "E&xit\tAlt-X", "Exit this simple sample")
+
+        # bind the menu event to an event handler
+        self.Bind(wx.EVT_MENU, self.OnTimeToClose, id=wx.ID_EXIT)
+
+        # and put the menu on the menubar
+        menuBar.Append(menu, "&File")
+        self.SetMenuBar(menuBar)
+
+        self.CreateStatusBar()
+
+        # Now create the Panel to put the other controls on.
+        panel = wx.Panel(self)
+
+        # and a few controls
+        text = wx.StaticText(panel, -1, "Hello World!")
+        text.SetFont(wx.Font(14, wx.SWISS, wx.NORMAL, wx.BOLD))
+        text.SetSize(text.GetBestSize())
+        btn = wx.Button(panel, -1, "Close")
+        funbtn = wx.Button(panel, -1, "Just for fun...")
+
+        # bind the button events to handlers
+        self.Bind(wx.EVT_BUTTON, self.OnTimeToClose, btn)
+        self.Bind(wx.EVT_BUTTON, self.OnFunButton, funbtn)
+
+        # Use a sizer to layout the controls, stacked vertically and with
+        # a 10 pixel border around each
+        sizer = wx.BoxSizer(wx.VERTICAL)
+        sizer.Add(text, 0, wx.ALL, 10)
+        sizer.Add(btn, 0, wx.ALL, 10)
+        sizer.Add(funbtn, 0, wx.ALL, 10)
+        panel.SetSizer(sizer)
+        panel.Layout()
+
+
+    def OnTimeToClose(self, evt):
+        """Event handler for the button click."""
+        print "See ya later!"
+        self.Close()
+
+    def OnFunButton(self, evt):
+        """Event handler for the button click."""
+        print "Having fun yet?"
+
+
+class MyApp(wx.App):
+    def OnInit(self):
+        frame = MyFrame(None, "Simple wxPython App")
+        self.SetTopWindow(frame)
+
+        print "Print statements go to this stdout window by default."
+
+        frame.Show(True)
+        return True
+
+app = wx.GetApp()
+if app is None:
+    app = MyApp(redirect=False, clearSigInt=False)
+
+try:
+    from IPython.lib.inputhook import appstart_wx
+    appstart_wx(app)
+except ImportError:
+    app.MainLoop()
+

IPython/__init__.py

@@ -1,47 +1,62 b''
 #!/usr/bin/env python
 # encoding: utf-8
 """
 IPython.
 
 IPython is a set of tools for interactive and exploratory computing in Python.
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2009  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 import os
 import sys
 from IPython.core import release
 
 #-----------------------------------------------------------------------------
 # Setup everything
 #-----------------------------------------------------------------------------
 
 
 if sys.version[0:3] < '2.4':
     raise ImportError('Python Version 2.4 or above is required for IPython.')
 
 
 # Make it easy to import extensions - they are always directly on pythonpath.
 # Therefore, non-IPython modules can be added to extensions directory
 sys.path.append(os.path.join(os.path.dirname(__file__), "extensions"))
 
-from IPython.core import iplib
+#-----------------------------------------------------------------------------
+# Setup the top level names
+#-----------------------------------------------------------------------------
 
+from IPython.core.iplib import InteractiveShell
+from IPython.core.error import TryNext
+
+from IPython.lib import (
+    enable_wx, disable_wx,
+    enable_gtk, disable_gtk,
+    enable_qt4, disable_qt4,
+    enable_tk, disable_tk,
+    set_inputhook, clear_inputhook,
+    current_gui, spin,
+    appstart_qt4, appstart_wx,
+    appstart_gtk, appstart_tk
+)
 
 # Release data
 __author__ = ''
 for author, email in release.authors.values():
     __author__ += author + ' <' + email + '>\n'
 __license__  = release.license
 __version__  = release.version
 __revision__ = release.revision
 

IPython/core/component.py

@@ -1,229 +1,233 b''
 #!/usr/bin/env python
 # encoding: utf-8
 """
 A lightweight component system for IPython.
 
 Authors:
 
 * Brian Granger
 * Fernando Perez
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2009  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 copy import deepcopy
 import datetime
 from weakref import WeakValueDictionary
 
 from IPython.utils.ipstruct import Struct
 from IPython.utils.traitlets import (
     HasTraitlets, TraitletError, MetaHasTraitlets, Instance, This
 )
 
 
 #-----------------------------------------------------------------------------
 # Helper classes for Components
 #-----------------------------------------------------------------------------
 
 
 class ComponentError(Exception):
     pass
 
 class MetaComponentTracker(type):
     """A metaclass that tracks instances of Components and its subclasses."""
 
     def __init__(cls, name, bases, d):
         super(MetaComponentTracker, cls).__init__(name, bases, d)
         cls.__instance_refs = WeakValueDictionary()
         cls.__numcreated = 0
 
     def __call__(cls, *args, **kw):
         """Called when *class* is called (instantiated)!!!
         
         When a Component or subclass is instantiated, this is called and
         the instance is saved in a WeakValueDictionary for tracking.
         """
 
         instance = super(MetaComponentTracker, cls).__call__(*args, **kw)
         for c in cls.__mro__:
             if issubclass(cls, c) and issubclass(c, Component):
                 c.__numcreated += 1
                 c.__instance_refs[c.__numcreated] = instance
         return instance
 
-    def get_instances(cls, name=None, klass=None, root=None):
+    def get_instances(cls, name=None, root=None):
         """Get all instances of cls and its subclasses.
 
         Parameters
         ----------
         name : str
             Limit to components with this name.
-        klass : class
-            Limit to components having isinstance(component, klass)
         root : Component or subclass
             Limit to components having this root.
         """
         instances = cls.__instance_refs.values()
         if name is not None:
             instances = [i for i in instances if i.name == name]
-        if klass is not None:
-            instances = [i for i in instances if isinstance(i, klass)]
         if root is not None:
             instances = [i for i in instances if i.root == root]
         return instances
 
-    def get_instances_by_condition(cls, call, name=None, klass=None, root=None):
+    def get_instances_by_condition(cls, call, name=None, root=None):
         """Get all instances of cls, i such that call(i)==True.
 
-        This also takes the ``name``, ``klass`` and ``root`` arguments of
+        This also takes the ``name`` and ``root`` arguments of
         :meth:`get_instance`
         """
-        return [i for i in cls.get_instances(name,klass,root) if call(i)]
+        return [i for i in cls.get_instances(name, root) if call(i)]
 
 
 class ComponentNameGenerator(object):
     """A Singleton to generate unique component names."""
 
     def __init__(self, prefix):
         self.prefix = prefix
         self.i = 0
 
     def __call__(self):
         count = self.i
         self.i += 1
         return "%s%s" % (self.prefix, count)
 
 
 ComponentNameGenerator = ComponentNameGenerator('ipython.component')
 
 
 class MetaComponent(MetaHasTraitlets, MetaComponentTracker):
     pass
 
 
 #-----------------------------------------------------------------------------
 # Component implementation
 #-----------------------------------------------------------------------------
 
 
 class Component(HasTraitlets):
 
     __metaclass__ = MetaComponent
 
     # Traitlets are fun!
     config = Instance(Struct,(),{})
     parent = This()
     root = This()
     created = None
 
     def __init__(self, parent, name=None, config=None):
         """Create a component given a parent and possibly and name and config.
 
         Parameters
         ----------
         parent : Component subclass
             The parent in the component graph.  The parent is used
             to get the root of the component graph.
         name : str
             The unique name of the component.  If empty, then a unique
             one will be autogenerated.
         config : Struct
             If this is empty, self.config = parent.config, otherwise
             self.config = config and root.config is ignored.  This argument
             should only be used to *override* the automatic inheritance of 
             parent.config.  If a caller wants to modify parent.config 
             (not override), the caller should make a copy and change 
             attributes and then pass the copy to this argument.
         
         Notes
         -----
         Subclasses of Component must call the :meth:`__init__` method of
         :class:`Component` *before* doing anything else and using 
         :func:`super`::
         
             class MyComponent(Component):
                 def __init__(self, parent, name=None, config=None):
                     super(MyComponent, self).__init__(parent, name, config)
                     # Then any other code you need to finish initialization.
 
         This ensures that the :attr:`parent`, :attr:`name` and :attr:`config`
         attributes are handled properly.
         """
         super(Component, self).__init__()
         self._children = []
         if name is None:
             self.name = ComponentNameGenerator()
         else:
             self.name = name
         self.root = self # This is the default, it is set when parent is set
         self.parent = parent     
         if config is not None:
             self.config = deepcopy(config)
         else:
             if self.parent is not None:
                 self.config = deepcopy(self.parent.config)
 
         self.created = datetime.datetime.now()
 
     #-------------------------------------------------------------------------
     # Static traitlet notifiations
     #-------------------------------------------------------------------------
 
     def _parent_changed(self, name, old, new):
         if old is not None:
             old._remove_child(self)
         if new is not None:
             new._add_child(self)
 
         if new is None:
             self.root = self
         else:
             self.root = new.root
 
     def _root_changed(self, name, old, new):
         if self.parent is None:
             if not (new is self):
                 raise ComponentError("Root not self, but parent is None.")
         else:
             if not self.parent.root is new:
                 raise ComponentError("Error in setting the root attribute: "
                                      "root != parent.root")
 
     def _config_changed(self, name, old, new):
+        """Update all the class traits having a config_key with the config.
+
+        For any class traitlet with a ``config_key`` metadata attribute, we
+        update the traitlet with the value of the corresponding config entry.
+
+        In the future, we might want to do a pop here so stale config info
+        is not passed onto children.
+        """
         # Get all traitlets with a config_key metadata entry
         traitlets = self.traitlets('config_key')
         for k, v in traitlets.items():
             try:
                 config_value = new[v.get_metadata('config_key')]
             except KeyError:
                 pass
             else:
                 setattr(self, k, config_value)
 
     @property
     def children(self):
         """A list of all my child components."""
         return self._children
 
     def _remove_child(self, child):
-        """A private method for removing children componenets."""
+        """A private method for removing children components."""
         if child in self._children:
             index = self._children.index(child)
             del self._children[index]
 
     def _add_child(self, child):
-        """A private method for adding children componenets."""
+        """A private method for adding children components."""
         if child not in self._children:
             self._children.append(child)
 
     def __repr__(self):
         return "<Component('%s')>" % self.name

IPython/core/ipapi.py

@@ -1,58 +1,59 b''
 #!/usr/bin/env python
 # encoding: utf-8
 """
 Oh my @#*%, where did ipapi go?
 
 Originally, this module was designed to be a public api for IPython.  It is
 now deprecated and replaced by :class:`IPython.core.Interactive` shell.
 Almost all of the methods that were here are now there, but possibly renamed.
 
 During our transition, we will keep this simple module with its :func:`get`
 function.  It too will eventually go away when the new component querying
 interface is fully used.
 
 Authors:
 
 * Brian Granger
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2009  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 IPython.core.error import TryNext, UsageError
 from IPython.core.component import Component
+from IPython.core.iplib import InteractiveShell
 
 #-----------------------------------------------------------------------------
 # Classes and functions
 #-----------------------------------------------------------------------------
 
 def get():
     """Get the most recently created InteractiveShell instance."""
-    insts = Component.get_instances(name='__IP')
+    insts = InteractiveShell.get_instances()
     most_recent = insts[0]
     for inst in insts[1:]:
         if inst.created > most_recent.created:
             most_recent = inst
     return most_recent
 
 def launch_new_instance():
     """Create a run a full blown IPython instance"""
     from IPython.core.ipapp import IPythonApp
     app = IPythonApp()
     app.start()
 
 
 
 
 
 
 
 

IPython/core/tests/test_component.py

@@ -1,194 +1,194 b''
 #!/usr/bin/env python
 # encoding: utf-8
 """
 Tests for IPython.core.component
 
 Authors:
 
 * Brian Granger
 * Fernando Perez (design help)
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2009  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 unittest import TestCase
 
 from IPython.core.component import Component, ComponentError
 from IPython.utils.traitlets import (
     TraitletError, Int, Float, Str
 )
 from IPython.utils.ipstruct import Struct
 
 
 #-----------------------------------------------------------------------------
 # Test cases
 #-----------------------------------------------------------------------------
 
 
 class TestComponentMeta(TestCase):
 
     def test_get_instances(self):
         class BaseComponent(Component):
             pass
         c1 = BaseComponent(None)
         c2 = BaseComponent(c1)
         self.assertEquals(BaseComponent.get_instances(),[c1,c2])
 
     def test_get_instances_subclass(self):
         class MyComponent(Component):
             pass
         class MyOtherComponent(MyComponent):
             pass
         c1 = MyComponent(None)
         c2 = MyOtherComponent(c1)
         c3 = MyOtherComponent(c2)
         self.assertEquals(MyComponent.get_instances(), [c1, c2, c3])
-        self.assertEquals(MyComponent.get_instances(klass=MyOtherComponent), [c2, c3])
+        self.assertEquals(MyOtherComponent.get_instances(), [c2, c3])
 
     def test_get_instances_root(self):
         class MyComponent(Component):
             pass
         class MyOtherComponent(MyComponent):
             pass
         c1 = MyComponent(None)
         c2 = MyOtherComponent(c1)
         c3 = MyOtherComponent(c2)
         c4 = MyComponent(None)
         c5 = MyComponent(c4)
         self.assertEquals(MyComponent.get_instances(root=c1), [c1, c2, c3])
         self.assertEquals(MyComponent.get_instances(root=c4), [c4, c5])
 
 
 class TestComponent(TestCase):
 
     def test_parent_child(self):
         c1 = Component(None)
         c2 = Component(c1)
         c3 = Component(c1)
         c4 = Component(c3)
         self.assertEquals(c1.parent, None)
         self.assertEquals(c2.parent, c1)
         self.assertEquals(c3.parent, c1)
         self.assertEquals(c4.parent, c3)
         self.assertEquals(c1.children, [c2, c3])
         self.assertEquals(c2.children, [])
         self.assertEquals(c3.children, [c4])
         self.assertEquals(c4.children, [])
 
     def test_root(self):
         c1 = Component(None)
         c2 = Component(c1)
         c3 = Component(c1)
         c4 = Component(c3)
         self.assertEquals(c1.root, c1.root)
         self.assertEquals(c2.root, c1)
         self.assertEquals(c3.root, c1)
         self.assertEquals(c4.root, c1)
 
     def test_change_parent(self):
         c1 = Component(None)
         c2 = Component(None)
         c3 = Component(c1)
         self.assertEquals(c3.root, c1)
         self.assertEquals(c3.parent, c1)
         self.assertEquals(c1.children,[c3])
         c3.parent = c2
         self.assertEquals(c3.root, c2)
         self.assertEquals(c3.parent, c2)
         self.assertEquals(c2.children,[c3])
         self.assertEquals(c1.children,[])
 
     def test_subclass_parent(self):
         c1 = Component(None)
         self.assertRaises(TraitletError, setattr, c1, 'parent', 10)
 
         class MyComponent(Component):
             pass
         c1 = Component(None)
         c2 = MyComponent(c1)
         self.assertEquals(MyComponent.parent.this_class, Component)
         self.assertEquals(c2.parent, c1)
 
     def test_bad_root(self):
         c1 = Component(None)
         c2 = Component(None)
         c3 = Component(None)
         self.assertRaises(ComponentError, setattr, c1, 'root', c2)
         c1.parent = c2
         self.assertEquals(c1.root, c2)
         self.assertRaises(ComponentError, setattr, c1, 'root', c3)
 
 
 class TestComponentConfig(TestCase):
 
     def test_default(self):
         c1 = Component(None)
         c2 = Component(c1)
         c3 = Component(c2)
         self.assertEquals(c1.config, c2.config)
         self.assertEquals(c2.config, c3.config)
 
     def test_custom(self):
         config = Struct()
         config.FOO = 'foo'
         config.BAR = 'bar'
         c1 = Component(None, config=config)
         c2 = Component(c1)
         c3 = Component(c2)
         self.assertEquals(c1.config, config)
         self.assertEquals(c2.config, config)
         self.assertEquals(c3.config, config)
         # Test that we always make copies
         self.assert_(c1.config is not config)
         self.assert_(c2.config is not config)
         self.assert_(c3.config is not config)
         self.assert_(c1.config is not c2.config)
         self.assert_(c2.config is not c3.config)
         
     def test_inheritance(self):
         class MyComponent(Component):
             a = Int(1, config_key='A')
             b = Float(1.0, config_key='B')
             c = Str('no config')
         config = Struct()
         config.A = 2
         config.B = 2.0
         c1 = MyComponent(None, config=config)
         c2 = MyComponent(c1)
         self.assertEquals(c1.a, config.A)
         self.assertEquals(c1.b, config.B)
         self.assertEquals(c2.a, config.A)
         self.assertEquals(c2.b, config.B)
         c4 = MyComponent(c2, config=Struct())
         self.assertEquals(c4.a, 1)
         self.assertEquals(c4.b, 1.0)
 
 class TestComponentName(TestCase):
 
     def test_default(self):
         class MyComponent(Component):
             pass
         c1 = Component(None)
         c2 = MyComponent(None)
         c3 = Component(c2)
         self.assertNotEquals(c1.name, c2.name)
         self.assertNotEquals(c1.name, c3.name)
 
     def test_manual(self):
         class MyComponent(Component):
             pass
         c1 = Component(None, name='foo')
         c2 = MyComponent(None, name='bar')
         c3 = Component(c2, name='bah')
         self.assertEquals(c1.name, 'foo')
         self.assertEquals(c2.name, 'bar')
         self.assertEquals(c3.name, 'bah')

IPython/lib/__init__.py

@@ -1,28 +1,31 b''
 #!/usr/bin/env python
 # encoding: utf-8
 """
 Extra capabilities for IPython
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2009  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 IPython.lib.inputhook import (
     enable_wx, disable_wx,
     enable_gtk, disable_gtk,
     enable_qt4, disable_qt4,
     enable_tk, disable_tk,
-    set_inputhook, clear_inputhook
+    set_inputhook, clear_inputhook,
+    current_gui, spin,
+    appstart_qt4, appstart_wx,
+    appstart_gtk, appstart_tk
 )
 
 #-----------------------------------------------------------------------------
 # Code
 #-----------------------------------------------------------------------------
  No newline at end of file

IPython/lib/inputhook.py

@@ -1,226 +1,525 b''
 #!/usr/bin/env python
 # encoding: utf-8
 """
 Inputhook management for GUI event loop integration.
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2009  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 import ctypes
 import sys
 
 #-----------------------------------------------------------------------------
-# Code
+# Constants
+#-----------------------------------------------------------------------------
+
+# Constants for identifying the GUI toolkits.
+GUI_WX = 'wx'
+GUI_QT4 = 'qt4'
+GUI_GTK = 'gtk'
+GUI_TK = 'tk'
+
+#-----------------------------------------------------------------------------
+# Utility classes
+#-----------------------------------------------------------------------------
+
+
+class _DummyMainloop(object):
+    """A special manager to hijack GUI mainloops that is mostly a no-op.
+
+    We are not using this class currently as it breaks GUI code that calls 
+    a mainloop function after the app has started to process pending events.
+    """
+    def __init__(self, ml, ihm, gui_type):
+        self.ml = ml
+        self.ihm = ihm
+        self.gui_type = gui_type
+
+    def __call__(self, *args, **kw):
+        if self.ihm.current_gui() == self.gui_type:
+            pass
+        else:
+            self.ml(*args, **kw)
+
+
+#-----------------------------------------------------------------------------
+# Appstart and spin functions
+#-----------------------------------------------------------------------------
+
+
+def appstart_qt4(app):
+    """Start the qt4 event loop in a way that plays with IPython.
+
+    When a qt4 app is run interactively in IPython, the event loop should
+    not be started.  This function checks to see if IPython's qt4 integration
+    is activated and if so, it passes.  If not, it will call the :meth:`exec_`
+    method of the main qt4 app.
+
+    This function should be used by users who want their qt4 scripts to work
+    both at the command line and in IPython.  These users should put the 
+    following logic at the bottom on their script, after they create a
+    :class:`QApplication` instance (called ``app`` here)::
+
+    try:
+        from IPython.lib.inputhook import appstart_qt4
+        appstart_qt4(app)
+    except ImportError:
+        app.exec_()
+    """
+    from PyQt4 import QtCore, QtGui
+
+    assert isinstance(app, QtCore.QCoreApplication)
+    if app is not None:
+        if current_gui() == GUI_QT4:
+            pass
+        else:
+            app.exec_()
+
+
+def appstart_wx(app):
+    """Start the wx event loop in a way that plays with IPython.
+
+    When a wx app is run interactively in IPython, the event loop should
+    not be started.  This function checks to see if IPython's wx integration
+    is activated and if so, it passes.  If not, it will call the 
+    :meth:`MainLoop` method of the main qt4 app.
+
+    This function should be used by users who want their wx scripts to work
+    both at the command line and in IPython.  These users should put the 
+    following logic at the bottom on their script, after they create a
+    :class:`App` instance (called ``app`` here)::
+
+    try:
+        from IPython.lib.inputhook import appstart_wx
+        appstart_wx(app)
+    except ImportError:
+        app.MainLoop()
+    """
+    import wx
+
+    assert isinstance(app, wx.App)
+    if app is not None:
+        if current_gui() == GUI_WX:
+            pass
+        else:
+            app.MainLoop()
+
+
+def appstart_tk(app):
+    """Start the tk event loop in a way that plays with IPython.
+
+    When a tk app is run interactively in IPython, the event loop should
+    not be started.  This function checks to see if IPython's tk integration
+    is activated and if so, it passes.  If not, it will call the 
+    :meth:`mainloop` method of the tk object passed to this method.
+
+    This function should be used by users who want their tk scripts to work
+    both at the command line and in IPython.  These users should put the 
+    following logic at the bottom on their script, after they create a
+    :class:`Tk` instance (called ``app`` here)::
+
+    try:
+        from IPython.lib.inputhook import appstart_tk
+        appstart_tk(app)
+    except ImportError:
+        app.mainloop()
+    """
+    if app is not None:
+        if current_gui() == GUI_TK:
+            pass
+        else:
+            app.mainloop()
+
+def appstart_gtk():
+    """Start the gtk event loop in a way that plays with IPython.
+
+    When a gtk app is run interactively in IPython, the event loop should
+    not be started.  This function checks to see if IPython's gtk integration
+    is activated and if so, it passes.  If not, it will call 
+    :func:`gtk.main`.  Unlike the other appstart implementations, this does
+    not take an ``app`` argument.
+
+    This function should be used by users who want their gtk scripts to work
+    both at the command line and in IPython.  These users should put the 
+    following logic at the bottom on their script::
+
+    try:
+        from IPython.lib.inputhook import appstart_gtk
+        appstart_gtk()
+    except ImportError:
+        gtk.main()
+    """
+    import gtk
+    if current_gui() == GUI_GTK:
+        pass
+    else:
+        gtk.main()
+
+#-----------------------------------------------------------------------------
+# Main InputHookManager class
 #-----------------------------------------------------------------------------
 
 
 class InputHookManager(object):
     """Manage PyOS_InputHook for different GUI toolkits.
 
     This class installs various hooks under ``PyOSInputHook`` to handle
     GUI event loop integration.
     """
     
     def __init__(self):
         self.PYFUNC = ctypes.PYFUNCTYPE(ctypes.c_int)
+        self._apps = {}
+        self._spinner_dict = {
+            GUI_QT4 : self._spin_qt4,
+            GUI_WX  : self._spin_wx,
+            GUI_GTK : self._spin_gtk,
+            GUI_TK  : self._spin_tk}
         self._reset()
 
     def _reset(self):
         self._callback_pyfunctype = None
         self._callback = None
         self._installed = False
         self._current_gui = None
 
-    def get_pyos_inputhook(self):
-        """Return the current PyOS_InputHook as a ctypes.c_void_p.
+    def _hijack_wx(self):
+        """Hijack the wx mainloop so a user calling it won't cause badness.
+
+        We are not currently using this as it breaks GUI code that calls a 
+        mainloop at anytime but startup.
+        """
+        import wx
+        if hasattr(wx, '_core_'): core = getattr(wx, '_core_')
+        elif hasattr(wx, '_core'): core = getattr(wx, '_core')
+        else: raise AttributeError('Could not find wx core module')
+        orig_mainloop = core.PyApp_MainLoop
+        core.PyApp_MainLoop = _DummyMainloop
+        return orig_mainloop
+
+    def _hijack_qt4(self):
+        """Hijack the qt4 mainloop so a user calling it won't cause badness.
+
+        We are not currently using this as it breaks GUI code that calls a 
+        mainloop at anytime but startup.
+        """
+        from PyQt4 import QtGui, QtCore
+        orig_mainloop = QtGui.qApp.exec_
+        dumb_ml = _DummyMainloop(orig_mainloop, self, GUI_QT4)
+        QtGui.qApp.exec_ = dumb_ml
+        QtGui.QApplication.exec_ = dumb_ml
+        QtCore.QCoreApplication.exec_ = dumb_ml
+        return orig_mainloop
+
+    def _hijack_gtk(self):
+        """Hijack the gtk mainloop so a user calling it won't cause badness.
+
+        We are not currently using this as it breaks GUI code that calls a 
+        mainloop at anytime but startup.
+        """
+        import gtk
+        orig_mainloop = gtk.main
+        dumb_ml = _DummyMainloop(orig_mainloop, self, GUI_GTK)
+        gtk.mainloop = dumb_ml
+        gtk.main = dumb_ml
+        return orig_mainloop
+
+    def _hijack_tk(self):
+        """Hijack the tk mainloop so a user calling it won't cause badness.
+
+        We are not currently using this as it breaks GUI code that calls a 
+        mainloop at anytime but startup.
+        """
+        import Tkinter
+        orig_mainloop = gtk.main
+        dumb_ml = _DummyMainloop(orig_mainloop, self, GUI_TK)
+        Tkinter.Misc.mainloop = dumb_ml
+        Tkinter.mainloop = dumb_ml
+
+    def _spin_qt4(self):
+        """Process all pending events in the qt4 event loop.
+
+        This is for internal IPython use only and user code should not call this.
+        Instead, they should issue the raw GUI calls themselves.
+        """
+        from PyQt4 import QtCore, QtGui
+
+        app = QtCore.QCoreApplication.instance()
+        if app is not None:
+            QtCore.QCoreApplication.processEvents(QtCore.QEventLoop.AllEvents)
+
+    def _spin_wx(self):
+        """Process all pending events in the wx event loop.
+
+        This is for internal IPython use only and user code should not call this.
+        Instead, they should issue the raw GUI calls themselves.
+        """
+        import wx
+        app = wx.GetApp()
+        if app is not None and wx.Thread_IsMain():
+            evtloop = wx.EventLoop()
+            ea = wx.EventLoopActivator(evtloop)
+            while evtloop.Pending():
+                evtloop.Dispatch()
+            app.ProcessIdle()
+            del ea
+
+    def _spin_gtk(self):
+        """Process all pending events in the gtk event loop.
+
+        This is for internal IPython use only and user code should not call this.
+        Instead, they should issue the raw GUI calls themselves.
+        """
+        import gtk
+        gtk.gdk.threads_enter()
+        while gtk.events_pending():
+            gtk.main_iteration(False)
+        gtk.gdk.flush()
+        gtk.gdk.threads_leave()
+
+    def _spin_tk(self):
+        """Process all pending events in the tk event loop.
+
+        This is for internal IPython use only and user code should not call this.
+        Instead, they should issue the raw GUI calls themselves.
         """
+        app = self._apps.get(GUI_TK)
+        if app is not None:
+            app.update()
+
+    def spin(self):
+        """Process pending events in the current gui.
+
+        This method is just provided for IPython to use internally if needed
+        for things like testing.  Third party projects should not call this
+        method, but instead should call the underlying GUI toolkit methods
+        that we are calling.
+        """
+        spinner = self._spinner_dict.get(self._current_gui, lambda: None)
+        spinner()
+
+    def get_pyos_inputhook(self):
+        """Return the current PyOS_InputHook as a ctypes.c_void_p."""
         return ctypes.c_void_p.in_dll(ctypes.pythonapi,"PyOS_InputHook")
 
     def get_pyos_inputhook_as_func(self):
-        """Return the current PyOS_InputHook as a ctypes.PYFUNCYPE.
-        """
+        """Return the current PyOS_InputHook as a ctypes.PYFUNCYPE."""
         return self.PYFUNC.in_dll(ctypes.pythonapi,"PyOS_InputHook")
 
     def set_inputhook(self, callback):
-        """Set PyOS_InputHook to callback and return the previous one.
-        """
+        """Set PyOS_InputHook to callback and return the previous one."""
         self._callback = callback
         self._callback_pyfunctype = self.PYFUNC(callback)
         pyos_inputhook_ptr = self.get_pyos_inputhook()
         original = self.get_pyos_inputhook_as_func()
         pyos_inputhook_ptr.value = \
             ctypes.cast(self._callback_pyfunctype, ctypes.c_void_p).value
         self._installed = True
         return original
 
     def clear_inputhook(self):
-        """Set PyOS_InputHook to NULL and return the previous one.
-        """
+        """Set PyOS_InputHook to NULL and return the previous one."""
         pyos_inputhook_ptr = self.get_pyos_inputhook()
         original = self.get_pyos_inputhook_as_func()
         pyos_inputhook_ptr.value = ctypes.c_void_p(None).value
         self._reset()
         return original
 
+    def clear_app_refs(self, gui=None):
+        """Clear IPython's internal reference to an application instance.
+
+        Whenever we create an app for a user on qt4 or wx, we hold a
+        reference to the app.  This is needed because in some cases bad things
+        can happen if a user doesn't hold a reference themselves.  This
+        method is provided to clear the references we are holding.
+
+        Parameters
+        ----------
+        gui : None or str
+            If None, clear all app references.  If ('wx', 'qt4') clear
+            the app for that toolkit.  References are not held for gtk or tk
+            as those toolkits don't have the notion of an app.
+        """
+        if gui is None:
+            self._apps = {}
+        elif self._apps.has_key(gui):
+            del self._apps[gui]
+
     def enable_wx(self, app=False):
         """Enable event loop integration with wxPython.
 
         Parameters
         ----------
         app : bool
             Create a running application object or not.
 
         Notes
         -----
-        This methods sets the PyOS_InputHook for wxPython, which allows
+        This methods sets the ``PyOS_InputHook`` for wxPython, which allows
         the wxPython to integrate with terminal based applications like
         IPython.
-        
-        Once this has been called, you can use wx interactively by doing::
-        
-            >>> import wx
-            >>> app = wx.App(redirect=False, clearSigInt=False)
-        
+
+        If ``app`` is True, we create an :class:`wx.App` as follows::
+
+            import wx
+            app = wx.App(redirect=False, clearSigInt=False)
+
         Both options this constructor are important for things to work
         properly in an interactive context.
-        
-        But, *don't start the event loop*.  That is handled automatically by
-        PyOS_InputHook.
+
+        But, we first check to see if an application has already been 
+        created.  If so, we simply return that instance.
         """
         from IPython.lib.inputhookwx import inputhook_wx
         self.set_inputhook(inputhook_wx)
-        self._current_gui = 'wx'
+        self._current_gui = GUI_WX
         if app:
             import wx
-            app = wx.App(redirect=False, clearSigInt=False)
+            app = wx.GetApp()
+            if app is None:
+                app = wx.App(redirect=False, clearSigInt=False)
+                self._apps[GUI_WX] = app
             return app
 
     def disable_wx(self):
         """Disable event loop integration with wxPython.
-        
+
         This merely sets PyOS_InputHook to NULL.
         """
         self.clear_inputhook()
 
     def enable_qt4(self, app=False):
         """Enable event loop integration with PyQt4.
         
         Parameters
         ----------
         app : bool
             Create a running application object or not.
 
         Notes
         -----
-        This methods sets the PyOS_InputHook for wxPython, which allows
+        This methods sets the PyOS_InputHook for PyQt4, which allows
         the PyQt4 to integrate with terminal based applications like
         IPython.
-        
-        Once this has been called, you can simply create a QApplication and
-        use it.  But, *don't start the event loop*.  That is handled
-        automatically by PyOS_InputHook.
+
+        If ``app`` is True, we create an :class:`QApplication` as follows::
+
+            from PyQt4 import QtCore
+            app = QtGui.QApplication(sys.argv)
+
+        But, we first check to see if an application has already been 
+        created.  If so, we simply return that instance.
         """
         from PyQt4 import QtCore
         # PyQt4 has had this since 4.3.1.  In version 4.2, PyOS_InputHook
         # was set when QtCore was imported, but if it ever got removed,
         # you couldn't reset it.  For earlier versions we can
         # probably implement a ctypes version.
         try:
             QtCore.pyqtRestoreInputHook()
         except AttributeError:
             pass
-        self._current_gui = 'qt4'
+        self._current_gui = GUI_QT4
         if app:
             from PyQt4 import QtGui
-            app = QtGui.QApplication(sys.argv)
+            app = QtCore.QCoreApplication.instance()
+            if app is None:
+                app = QtGui.QApplication(sys.argv)
+                self._apps[GUI_QT4] = app
             return app
 
     def disable_qt4(self):
         """Disable event loop integration with PyQt4.
-        
+
         This merely sets PyOS_InputHook to NULL.
         """
         self.clear_inputhook()
 
     def enable_gtk(self, app=False):
         """Enable event loop integration with PyGTK.
 
         Parameters
         ----------
         app : bool
-            Create a running application object or not.
+            Create a running application object or not.  Because gtk does't
+            have an app class, this does nothing.
 
         Notes
         -----
         This methods sets the PyOS_InputHook for PyGTK, which allows
         the PyGTK to integrate with terminal based applications like
         IPython.
-        
-        Once this has been called, you can simple create PyGTK objects and
-        use them.  But, *don't start the event loop*.  That is handled
-        automatically by PyOS_InputHook.
         """
         import gtk
         try:
             gtk.set_interactive(True)
-            self._current_gui = 'gtk'
+            self._current_gui = GUI_GTK
         except AttributeError:
             # For older versions of gtk, use our own ctypes version
             from IPython.lib.inputhookgtk import inputhook_gtk
-            add_inputhook(inputhook_gtk)
+            self.set_inputhook(inputhook_gtk)
+            self._current_gui = GUI_GTK
 
     def disable_gtk(self):
         """Disable event loop integration with PyGTK.
         
         This merely sets PyOS_InputHook to NULL.
         """
         self.clear_inputhook()
 
     def enable_tk(self, app=False):
         """Enable event loop integration with Tk.
 
         Parameters
         ----------
         app : bool
             Create a running application object or not.
 
         Notes
         -----
         Currently this is a no-op as creating a :class:`Tkinter.Tk` object 
         sets ``PyOS_InputHook``.
         """
-        self._current_gui = 'tk'
+        self._current_gui = GUI_TK
+        if app:
+            import Tkinter
+            app = Tkinter.Tk()
+            app.withdraw()
+            self._apps[GUI_TK] = app
+            return app
 
     def disable_tk(self):
         """Disable event loop integration with Tkinter.
         
         This merely sets PyOS_InputHook to NULL.
         """
         self.clear_inputhook()
 
     def current_gui(self):
         """Return a string indicating the currently active GUI or None."""
         return self._current_gui
 
 inputhook_manager = InputHookManager()
 
 enable_wx = inputhook_manager.enable_wx
 disable_wx = inputhook_manager.disable_wx
 enable_qt4 = inputhook_manager.enable_qt4
 disable_qt4 = inputhook_manager.disable_qt4
 enable_gtk = inputhook_manager.enable_gtk
 disable_gtk = inputhook_manager.disable_gtk
 enable_tk = inputhook_manager.enable_tk
 disable_tk = inputhook_manager.disable_tk
 clear_inputhook = inputhook_manager.clear_inputhook
 set_inputhook = inputhook_manager.set_inputhook
-current_gui = inputhook_manager.current_gui
  No newline at end of file
+current_gui = inputhook_manager.current_gui
+clear_app_refs = inputhook_manager.clear_app_refs
+spin = inputhook_manager.spin

IPython/lib/inputhookwx.py

@@ -1,153 +1,162 b''
 #!/usr/bin/env python
 # encoding: utf-8
 
 """
 Enable wxPython to be used interacive by setting PyOS_InputHook.
 
 Authors:  Robin Dunn, Brian Granger, Ondrej Certik
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2009  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 import os
+import signal
 import sys
 import time
 from timeit import default_timer as clock
 import wx
 
 if os.name == 'posix':
     import select
 elif sys.platform == 'win32':
     import msvcrt
 
 #-----------------------------------------------------------------------------
 # Code
 #-----------------------------------------------------------------------------
 
 def stdin_ready():
     if os.name == 'posix':
         infds, outfds, erfds = select.select([sys.stdin],[],[],0)
         if infds:
             return True
         else:
             return False
     elif sys.platform == 'win32':
         return msvcrt.kbhit()
 
 
 def inputhook_wx1():
     """Run the wx event loop by processing pending events only.
     
     This approach seems to work, but its performance is not great as it 
     relies on having PyOS_InputHook called regularly.
     """
     app = wx.GetApp()
     if app is not None:
         assert wx.Thread_IsMain()
 
         # Make a temporary event loop and process system events until
         # there are no more waiting, then allow idle events (which
         # will also deal with pending or posted wx events.)
         evtloop = wx.EventLoop()
         ea = wx.EventLoopActivator(evtloop)
         while evtloop.Pending():
             evtloop.Dispatch()
         app.ProcessIdle()
         del ea
     return 0
 
 class EventLoopTimer(wx.Timer):
 
     def __init__(self, func):
         self.func = func
         wx.Timer.__init__(self)
 
     def Notify(self):
         self.func()
 
 class EventLoopRunner(object):
 
     def Run(self, time):
         self.evtloop = wx.EventLoop()
         self.timer = EventLoopTimer(self.check_stdin)
         self.timer.Start(time)
         self.evtloop.Run()
 
     def check_stdin(self):
         if stdin_ready():
             self.timer.Stop()
             self.evtloop.Exit()
 
 def inputhook_wx2():
     """Run the wx event loop, polling for stdin.
     
     This version runs the wx eventloop for an undetermined amount of time,
     during which it periodically checks to see if anything is ready on
     stdin.  If anything is ready on stdin, the event loop exits.
     
     The argument to elr.Run controls how often the event loop looks at stdin.
     This determines the responsiveness at the keyboard.  A setting of 1000
     enables a user to type at most 1 char per second.  I have found that a
     setting of 10 gives good keyboard response.  We can shorten it further, 
     but eventually performance would suffer from calling select/kbhit too 
     often.
     """
     app = wx.GetApp()
     if app is not None:
         assert wx.Thread_IsMain()
         elr = EventLoopRunner()
         # As this time is made shorter, keyboard response improves, but idle
         # CPU load goes up.  10 ms seems like a good compromise.
         elr.Run(time=10)  # CHANGE time here to control polling interval
     return 0
 
 def inputhook_wx3():
     """Run the wx event loop by processing pending events only.
     
     This is like inputhook_wx1, but it keeps processing pending events
     until stdin is ready.  After processing all pending events, a call to 
     time.sleep is inserted.  This is needed, otherwise, CPU usage is at 100%.
     This sleep time should be tuned though for best performance.
     """
     app = wx.GetApp()
     if app is not None:
         assert wx.Thread_IsMain()
 
+        # The import of wx on Linux sets the handler for signal.SIGINT
+        # to 0.  This is a bug in wx or gtk.  We fix by just setting it
+        # back to the Python default.
+        if not callable(signal.getsignal(signal.SIGINT)):
+            signal.signal(signal.SIGINT, signal.default_int_handler)
+
         evtloop = wx.EventLoop()
         ea = wx.EventLoopActivator(evtloop)
         t = clock()
         while not stdin_ready():
             while evtloop.Pending():
                 t = clock()
                 evtloop.Dispatch()
             app.ProcessIdle()
             # We need to sleep at this point to keep the idle CPU load
             # low.  However, if sleep to long, GUI response is poor.  As 
             # a compromise, we watch how often GUI events are being processed
             # and switch between a short and long sleep time.  Here are some
             # stats useful in helping to tune this.
             # time    CPU load
             # 0.001   13%
             # 0.005   3%
             # 0.01    1.5%
-            # 0.05    0.5%            
+            # 0.05    0.5%
+            if clock()-t > 1.0:
+                time.sleep(1.0)
             if clock()-t > 0.1:
                 # Few GUI events coming in, so we can sleep longer
                 time.sleep(0.05)
             else:
                 # Many GUI events coming in, so sleep only very little
                 time.sleep(0.001)
         del ea
     return 0
 
 # This is our default implementation
 inputhook_wx = inputhook_wx3
  No newline at end of file

docs/source/interactive/reference.txt

@@ -1,1539 +1,1542 b''
 =================
 IPython reference
 =================
 
 .. _command_line_options:
 
 Command-line usage
 ==================
 
 You start IPython with the command::
 
     $ ipython [options] files
 
 If invoked with no options, it executes all the files listed in sequence
 and drops you into the interpreter while still acknowledging any options
 you may have set in your ipythonrc file. This behavior is different from
 standard Python, which when called as python -i will only execute one
 file and ignore your configuration setup.
 
 Please note that some of the configuration options are not available at
 the command line, simply because they are not practical here. Look into
 your ipythonrc configuration file for details on those. This file
 typically installed in the $HOME/.ipython directory. For Windows users,
 $HOME resolves to C:\\Documents and Settings\\YourUserName in most
 instances. In the rest of this text, we will refer to this directory as
 IPYTHONDIR.
 
 
 
 Special Threading Options
 -------------------------
 
 Previously IPython had command line options for controlling GUI event loop
 integration (-gthread, -qthread, -q4thread, -wthread, -pylab). As of IPython
 version 0.11, these have been deprecated. Please see the new ``%gui``
 magic command or :ref:`this section <gui_support>` for details on the new
 interface.
 
 Regular Options
 ---------------
 
 After the above threading options have been given, regular options can
 follow in any order. All options can be abbreviated to their shortest
 non-ambiguous form and are case-sensitive. One or two dashes can be
 used. Some options have an alternate short form, indicated after a ``|``.
 
 Most options can also be set from your ipythonrc configuration file. See
 the provided example for more details on what the options do. Options
 given at the command line override the values set in the ipythonrc file.
 
 All options with a [no] prepended can be specified in negated form
 (-nooption instead of -option) to turn the feature off.
 
     -help  print a help message and exit.
 
     -pylab
     Deprecated.  See :ref:`Matplotlib support <matplotlib_support>`
     for more details.
 
     -autocall <val>
 	Make IPython automatically call any callable object even if you
 	didn't type explicit parentheses. For example, 'str 43' becomes
 	'str(43)' automatically. The value can be '0' to disable the feature,
 	'1' for smart autocall, where it is not applied if there are no more
 	arguments on the line, and '2' for full autocall, where all callable
 	objects are automatically called (even if no arguments are
 	present). The default is '1'.
 
     -[no]autoindent    
 	Turn automatic indentation on/off.
 
     -[no]automagic 
 	make magic commands automatic (without needing their first character
 	to be %). Type %magic at the IPython prompt for more information.
 
     -[no]autoedit_syntax 
 	When a syntax error occurs after editing a file, automatically
 	open the file to the trouble causing line for convenient
 	fixing.
 
     -[no]banner		Print the initial information banner (default on).
 
     -c <command>
 	execute the given command string. This is similar to the -c
 	option in the normal Python interpreter.
 
     -cache_size, cs <n> 
 	size of the output cache (maximum number of entries to hold in
 	memory). The default is 1000, you can change it permanently in your
 	config file. Setting it to 0 completely disables the caching system,
 	and the minimum value accepted is 20 (if you provide a value less than
 	20, it is reset to 0 and a warning is issued) This limit is defined
 	because otherwise you'll spend more time re-flushing a too small cache
 	than working.
 
     -classic, cl 
 	Gives IPython a similar feel to the classic Python
 	prompt.
 
     -colors <scheme> 
 	Color scheme for prompts and exception reporting. Currently
 	implemented: NoColor, Linux and LightBG.
 
     -[no]color_info 
 	IPython can display information about objects via a set of functions,
 	and optionally can use colors for this, syntax highlighting source
 	code and various other elements.  However, because this information is
 	passed through a pager (like 'less') and many pagers get confused with
 	color codes, this option is off by default. You can test it and turn
 	it on permanently in your ipythonrc file if it works for you. As a
 	reference, the 'less' pager supplied with Mandrake 8.2 works ok, but
 	that in RedHat 7.2 doesn't.
 
 	Test it and turn it on permanently if it works with your
 	system. The magic function %color_info allows you to toggle this
 	interactively for testing.
 
     -[no]debug 
 	Show information about the loading process. Very useful to pin down
 	problems with your configuration files or to get details about
 	session restores.
 
     -[no]deep_reload: 
 	IPython can use the deep_reload module which reloads changes in
 	modules recursively (it replaces the reload() function, so you don't
 	need to change anything to use it).  deep_reload() forces a full
 	reload of modules whose code may have changed, which the default
 	reload() function does not.
 
 	When deep_reload is off, IPython will use the normal reload(),
 	but deep_reload will still be available as dreload(). This
 	feature is off by default [which means that you have both
 	normal reload() and dreload()].
 
     -editor <name>
 	Which editor to use with the %edit command. By default,
 	IPython will honor your EDITOR environment variable (if not
 	set, vi is the Unix default and notepad the Windows one).
 	Since this editor is invoked on the fly by IPython and is
 	meant for editing small code snippets, you may want to use a
 	small, lightweight editor here (in case your default EDITOR is
 	something like Emacs).
 
     -ipythondir <name> 
 	name of your IPython configuration directory IPYTHONDIR. This
 	can also be specified through the environment variable
 	IPYTHONDIR.
 
     -log, l 
 	generate a log file of all input. The file is named
 	ipython_log.py in your current directory (which prevents logs
 	from multiple IPython sessions from trampling each other). You
 	can use this to later restore a session by loading your
 	logfile as a file to be executed with option -logplay (see
 	below).
 
     -logfile, lf <name>   specify the name of your logfile.
 
     -logplay, lp <name> 
 
       you can replay a previous log. For restoring a session as close as
       possible to the state you left it in, use this option (don't just run
       the logfile). With -logplay, IPython will try to reconstruct the
       previous working environment in full, not just execute the commands in
       the logfile.
 
       When a session is restored, logging is automatically turned on
       again with the name of the logfile it was invoked with (it is
       read from the log header). So once you've turned logging on for
       a session, you can quit IPython and reload it as many times as
       you want and it will continue to log its history and restore
       from the beginning every time.
       
       Caveats: there are limitations in this option. The history
       variables _i*,_* and _dh don't get restored properly. In the
       future we will try to implement full session saving by writing
       and retrieving a 'snapshot' of the memory state of IPython. But
       our first attempts failed because of inherent limitations of
       Python's Pickle module, so this may have to wait.
 
     -[no]messages   
 	Print messages which IPython collects about its startup
 	process (default on).
 
     -[no]pdb
 	Automatically call the pdb debugger after every uncaught
 	exception. If you are used to debugging using pdb, this puts
 	you automatically inside of it after any call (either in
 	IPython or in code called by it) which triggers an exception
 	which goes uncaught.
 
     -pydb
 	Makes IPython use the third party "pydb" package as debugger,
 	instead of pdb. Requires that pydb is installed.
 	
     -[no]pprint
 	ipython can optionally use the pprint (pretty printer) module
 	for displaying results. pprint tends to give a nicer display
 	of nested data structures. If you like it, you can turn it on
 	permanently in your config file (default off).
 
     -profile, p <name>
 
 	assume that your config file is ipythonrc-<name> or
 	ipy_profile_<name>.py (looks in current dir first, then in
 	IPYTHONDIR).  This is a quick way to keep and load multiple
 	config files for different tasks, especially if you use the
 	include option of config files. You can keep a basic
 	IPYTHONDIR/ipythonrc file and then have other 'profiles' which
 	include this one and load extra things for particular
 	tasks. For example:
 
 	1. $HOME/.ipython/ipythonrc : load basic things you always want.
 	2. $HOME/.ipython/ipythonrc-math : load (1) and basic math-related modules.
 	3. $HOME/.ipython/ipythonrc-numeric : load (1) and Numeric and plotting modules.
 
 	Since it is possible to create an endless loop by having
 	circular file inclusions, IPython will stop if it reaches 15
 	recursive inclusions.
 
     -prompt_in1, pi1 <string>
 
         Specify the string used for input prompts. Note that if you are using
 	numbered prompts, the number is represented with a '\#' in the
 	string. Don't forget to quote strings with spaces embedded in
 	them. Default: 'In [\#]:'.  The :ref:`prompts section <prompts>`
 	discusses in detail all the available escapes to customize your
 	prompts.
 
     -prompt_in2, pi2 <string>
 	Similar to the previous option, but used for the continuation
 	prompts. The special sequence '\D' is similar to '\#', but
 	with all digits replaced dots (so you can have your
 	continuation prompt aligned with your input prompt).  Default:
 	' .\D.:' (note three spaces at the start for alignment with
 	'In [\#]').
 
     -prompt_out,po <string> 
 	String used for output prompts, also uses numbers like
 	prompt_in1. Default: 'Out[\#]:'
 
     -quick   start in bare bones mode (no config file loaded).
 
     -rcfile <name>   
 	name of your IPython resource configuration file. Normally
 	IPython loads ipythonrc (from current directory) or
 	IPYTHONDIR/ipythonrc.
 
 	If the loading of your config file fails, IPython starts with
 	a bare bones configuration (no modules loaded at all).
 
     -[no]readline
 	use the readline library, which is needed to support name
 	completion and command history, among other things.  It is
 	enabled by default, but may cause problems for users of
 	X/Emacs in Python comint or shell buffers.
 
 	Note that X/Emacs 'eterm' buffers (opened with M-x term) support
 	IPython's readline and syntax coloring fine, only 'emacs' (M-x
 	shell and C-c !) buffers do not.
 
     -screen_length, sl <n>
 	number of lines of your screen. This is used to control
 	printing of very long strings. Strings longer than this number
 	of lines will be sent through a pager instead of directly
 	printed.
 
 	The default value for this is 0, which means IPython will
 	auto-detect your screen size every time it needs to print certain
 	potentially long strings (this doesn't change the behavior of the
 	'print' keyword, it's only triggered internally). If for some
 	reason this isn't working well (it needs curses support), specify
 	it yourself. Otherwise don't change the default.
 
     -separate_in, si <string>
 
 	separator before input prompts.
 	Default: '\n'
 
     -separate_out, so <string>  
         separator before output prompts.
         Default: nothing.
 
     -separate_out2, so2
 	separator after output prompts.
 	Default: nothing.
 	For these three options, use the value 0 to specify no separator.
 
     -nosep   
 	shorthand for '-SeparateIn 0 -SeparateOut 0 -SeparateOut2
 	0'. Simply removes all input/output separators.
 
     -upgrade 
 	allows you to upgrade your IPYTHONDIR configuration when you
 	install a new version of IPython. Since new versions may
 	include new command line options or example files, this copies
 	updated ipythonrc-type files. However, it backs up (with a
 	.old extension) all files which it overwrites so that you can
 	merge back any customizations you might have in your personal
 	files. Note that you should probably use %upgrade instead,
 	it's a safer alternative.
 
 
     -Version    print version information and exit.
 
     -wxversion <string> 
     Deprecated.
 
     -xmode <modename>
 
 	Mode for exception reporting.
 
 	Valid modes: Plain, Context and Verbose.
 
 	* Plain: similar to python's normal traceback printing.
 	* Context: prints 5 lines of context source code around each
 	  line in the traceback.
 	* Verbose: similar to Context, but additionally prints the
 	  variables currently visible where the exception happened
 	  (shortening their strings if too long). This can potentially be
 	  very slow, if you happen to have a huge data structure whose
 	  string representation is complex to compute. Your computer may
 	  appear to freeze for a while with cpu usage at 100%. If this
 	  occurs, you can cancel the traceback with Ctrl-C (maybe hitting it
 	  more than once).
 
 Interactive use
 ===============
 
 Warning: IPython relies on the existence of a global variable called
 _ip which controls the shell itself. If you redefine _ip to anything,
 bizarre behavior will quickly occur.
 
 Other than the above warning, IPython is meant to work as a drop-in
 replacement for the standard interactive interpreter. As such, any code
 which is valid python should execute normally under IPython (cases where
 this is not true should be reported as bugs). It does, however, offer
 many features which are not available at a standard python prompt. What
 follows is a list of these.
 
 
 Caution for Windows users
 -------------------------
 
 Windows, unfortunately, uses the '\' character as a path
 separator. This is a terrible choice, because '\' also represents the
 escape character in most modern programming languages, including
 Python. For this reason, using '/' character is recommended if you
 have problems with ``\``.  However, in Windows commands '/' flags
 options, so you can not use it for the root directory. This means that
 paths beginning at the root must be typed in a contrived manner like:
 ``%copy \opt/foo/bar.txt \tmp``
 
 .. _magic:
 
 Magic command system
 --------------------
 
 IPython will treat any line whose first character is a % as a special
 call to a 'magic' function. These allow you to control the behavior of
 IPython itself, plus a lot of system-type features. They are all
 prefixed with a % character, but parameters are given without
 parentheses or quotes.
 
 Example: typing '%cd mydir' (without the quotes) changes you working
 directory to 'mydir', if it exists.
 
 If you have 'automagic' enabled (in your ipythonrc file, via the command
 line option -automagic or with the %automagic function), you don't need
 to type in the % explicitly. IPython will scan its internal list of
 magic functions and call one if it exists. With automagic on you can
 then just type 'cd mydir' to go to directory 'mydir'. The automagic
 system has the lowest possible precedence in name searches, so defining
 an identifier with the same name as an existing magic function will
 shadow it for automagic use. You can still access the shadowed magic
 function by explicitly using the % character at the beginning of the line.
 
 An example (with automagic on) should clarify all this::
 
     In [1]: cd ipython # %cd is called by automagic
 
     /home/fperez/ipython
 
     In [2]: cd=1 # now cd is just a variable
 
     In [3]: cd .. # and doesn't work as a function anymore
 
     ------------------------------
 
         File "<console>", line 1
 
           cd ..
 
               ^
 
     SyntaxError: invalid syntax
 
     In [4]: %cd .. # but %cd always works
 
     /home/fperez
 
     In [5]: del cd # if you remove the cd variable
 
     In [6]: cd ipython # automagic can work again
 
     /home/fperez/ipython
 
 You can define your own magic functions to extend the system. The
 following example defines a new magic command, %impall::
 
     import IPython.ipapi 
 
     ip = IPython.ipapi.get()
 
     def doimp(self, arg):
 
         ip = self.api
 
         ip.ex("import %s; reload(%s); from %s import *" % (
 
         arg,arg,arg)
 
         )
 
     ip.expose_magic('impall', doimp)
 
 You can also define your own aliased names for magic functions. In your
 ipythonrc file, placing a line like::
 
     execute __IP.magic_cl = __IP.magic_clear
 
 will define %cl as a new name for %clear.
 
 Type %magic for more information, including a list of all available
 magic functions at any time and their docstrings. You can also type
 %magic_function_name? (see sec. 6.4 <#sec:dyn-object-info> for
 information on the '?' system) to get information about any particular
 magic function you are interested in.
 
 The API documentation for the :mod:`IPython.Magic` module contains the full
 docstrings of all currently available magic commands.
 
 
 Access to the standard Python help
 ----------------------------------
 
 As of Python 2.1, a help system is available with access to object docstrings
 and the Python manuals. Simply type 'help' (no quotes) to access it. You can
 also type help(object) to obtain information about a given object, and
 help('keyword') for information on a keyword. As noted :ref:`here
 <accessing_help>`, you need to properly configure your environment variable
 PYTHONDOCS for this feature to work correctly.
 
 .. _dynamic_object_info:
 
 Dynamic object information
 --------------------------
 
 Typing ?word or word? prints detailed information about an object. If
 certain strings in the object are too long (docstrings, code, etc.) they
 get snipped in the center for brevity. This system gives access variable
 types and values, full source code for any object (if available),
 function prototypes and other useful information.
 
 Typing ??word or word?? gives access to the full information without
 snipping long strings. Long strings are sent to the screen through the
 less pager if longer than the screen and printed otherwise. On systems
 lacking the less command, IPython uses a very basic internal pager.
 
 The following magic functions are particularly useful for gathering
 information about your working environment. You can get more details by
 typing %magic or querying them individually (use %function_name? with or
 without the %), this is just a summary:
 
     * **%pdoc <object>**: Print (or run through a pager if too long) the
       docstring for an object. If the given object is a class, it will
       print both the class and the constructor docstrings.
     * **%pdef <object>**: Print the definition header for any callable
       object. If the object is a class, print the constructor information.
     * **%psource <object>**: Print (or run through a pager if too long)
       the source code for an object.
     * **%pfile <object>**: Show the entire source file where an object was
       defined via a pager, opening it at the line where the object
       definition begins.
     * **%who/%whos**: These functions give information about identifiers
       you have defined interactively (not things you loaded or defined
       in your configuration files). %who just prints a list of
       identifiers and %whos prints a table with some basic details about
       each identifier.
 
 Note that the dynamic object information functions (?/??, %pdoc, %pfile,
 %pdef, %psource) give you access to documentation even on things which
 are not really defined as separate identifiers. Try for example typing
 {}.get? or after doing import os, type os.path.abspath??.
 
 
 .. _readline:
 
 Readline-based features
 -----------------------
 
 These features require the GNU readline library, so they won't work if
 your Python installation lacks readline support. We will first describe
 the default behavior IPython uses, and then how to change it to suit
 your preferences.
 
 
 Command line completion
 +++++++++++++++++++++++
 
 At any time, hitting TAB will complete any available python commands or
 variable names, and show you a list of the possible completions if
 there's no unambiguous one. It will also complete filenames in the
 current directory if no python names match what you've typed so far.
 
 
 Search command history
 ++++++++++++++++++++++
 
 IPython provides two ways for searching through previous input and thus
 reduce the need for repetitive typing:
 
    1. Start typing, and then use Ctrl-p (previous,up) and Ctrl-n
       (next,down) to search through only the history items that match
       what you've typed so far. If you use Ctrl-p/Ctrl-n at a blank
       prompt, they just behave like normal arrow keys.
    2. Hit Ctrl-r: opens a search prompt. Begin typing and the system
       searches your history for lines that contain what you've typed so
       far, completing as much as it can.
 
 
 Persistent command history across sessions
 ++++++++++++++++++++++++++++++++++++++++++
 
 IPython will save your input history when it leaves and reload it next
 time you restart it. By default, the history file is named
 $IPYTHONDIR/history, but if you've loaded a named profile,
 '-PROFILE_NAME' is appended to the name. This allows you to keep
 separate histories related to various tasks: commands related to
 numerical work will not be clobbered by a system shell history, for
 example.
 
 
 Autoindent
 ++++++++++
 
 IPython can recognize lines ending in ':' and indent the next line,
 while also un-indenting automatically after 'raise' or 'return'.
 
 This feature uses the readline library, so it will honor your ~/.inputrc
 configuration (or whatever file your INPUTRC variable points to). Adding
 the following lines to your .inputrc file can make indenting/unindenting
 more convenient (M-i indents, M-u unindents)::
 
     $if Python 
     "\M-i": "    "  
     "\M-u": "\d\d\d\d"  
     $endif
 
 Note that there are 4 spaces between the quote marks after "M-i" above.
 
 Warning: this feature is ON by default, but it can cause problems with
 the pasting of multi-line indented code (the pasted code gets
 re-indented on each line). A magic function %autoindent allows you to
 toggle it on/off at runtime. You can also disable it permanently on in
 your ipythonrc file (set autoindent 0).
 
 
 Customizing readline behavior
 +++++++++++++++++++++++++++++
 
 All these features are based on the GNU readline library, which has an
 extremely customizable interface. Normally, readline is configured via a
 file which defines the behavior of the library; the details of the
 syntax for this can be found in the readline documentation available
 with your system or on the Internet. IPython doesn't read this file (if
 it exists) directly, but it does support passing to readline valid
 options via a simple interface. In brief, you can customize readline by
 setting the following options in your ipythonrc configuration file (note
 that these options can not be specified at the command line):
 
     * **readline_parse_and_bind**: this option can appear as many times as
       you want, each time defining a string to be executed via a
       readline.parse_and_bind() command. The syntax for valid commands
       of this kind can be found by reading the documentation for the GNU
       readline library, as these commands are of the kind which readline
       accepts in its configuration file.
     * **readline_remove_delims**: a string of characters to be removed
       from the default word-delimiters list used by readline, so that
       completions may be performed on strings which contain them. Do not
       change the default value unless you know what you're doing.
     * **readline_omit__names**: when tab-completion is enabled, hitting
       <tab> after a '.' in a name will complete all attributes of an
       object, including all the special methods whose names include
       double underscores (like __getitem__ or __class__). If you'd
       rather not see these names by default, you can set this option to
       1. Note that even when this option is set, you can still see those
       names by explicitly typing a _ after the period and hitting <tab>:
       'name._<tab>' will always complete attribute names starting with '_'.
       
       This option is off by default so that new users see all
       attributes of any objects they are dealing with.
 
 You will find the default values along with a corresponding detailed
 explanation in your ipythonrc file.
 
 
 Session logging and restoring
 -----------------------------
 
 You can log all input from a session either by starting IPython with the
 command line switches -log or -logfile (see :ref:`here <command_line_options>`)
 or by activating the logging at any moment with the magic function %logstart.
 
 Log files can later be reloaded with the -logplay option and IPython
 will attempt to 'replay' the log by executing all the lines in it, thus
 restoring the state of a previous session. This feature is not quite
 perfect, but can still be useful in many cases.
 
 The log files can also be used as a way to have a permanent record of
 any code you wrote while experimenting. Log files are regular text files
 which you can later open in your favorite text editor to extract code or
 to 'clean them up' before using them to replay a session.
 
 The %logstart function for activating logging in mid-session is used as
 follows:
 
 %logstart [log_name [log_mode]]
 
 If no name is given, it defaults to a file named 'log' in your
 IPYTHONDIR directory, in 'rotate' mode (see below).
 
 '%logstart name' saves to file 'name' in 'backup' mode. It saves your
 history up to that point and then continues logging.
 
 %logstart takes a second optional parameter: logging mode. This can be
 one of (note that the modes are given unquoted):
 
     * [over:] overwrite existing log_name.
     * [backup:] rename (if exists) to log_name~ and start log_name.
     * [append:] well, that says it.
     * [rotate:] create rotating logs log_name.1~, log_name.2~, etc.
 
 The %logoff and %logon functions allow you to temporarily stop and
 resume logging to a file which had previously been started with
 %logstart. They will fail (with an explanation) if you try to use them
 before logging has been started.
 
 .. _system_shell_access:
 
 System shell access
 -------------------
 
 Any input line beginning with a ! character is passed verbatim (minus
 the !, of course) to the underlying operating system. For example,
 typing !ls will run 'ls' in the current directory.
 
 Manual capture of command output
 --------------------------------
 
 If the input line begins with two exclamation marks, !!, the command is
 executed but its output is captured and returned as a python list, split
 on newlines. Any output sent by the subprocess to standard error is
 printed separately, so that the resulting list only captures standard
 output. The !! syntax is a shorthand for the %sx magic command.
 
 Finally, the %sc magic (short for 'shell capture') is similar to %sx,
 but allowing more fine-grained control of the capture details, and
 storing the result directly into a named variable. The direct use of 
 %sc is now deprecated, and you should ise the ``var = !cmd`` syntax
 instead.
 
 IPython also allows you to expand the value of python variables when
 making system calls. Any python variable or expression which you prepend
 with $ will get expanded before the system call is made::
 
     In [1]: pyvar='Hello world' 
     In [2]: !echo "A python variable: $pyvar"  
     A python variable: Hello world
 
 If you want the shell to actually see a literal $, you need to type it
 twice::
 
     In [3]: !echo "A system variable: $$HOME"  
     A system variable: /home/fperez
 
 You can pass arbitrary expressions, though you'll need to delimit them
 with {} if there is ambiguity as to the extent of the expression::
 
     In [5]: x=10 
     In [6]: y=20 
     In [13]: !echo $x+y  
     10+y  
     In [7]: !echo ${x+y}  
     30
 
 Even object attributes can be expanded::
 
     In [12]: !echo $sys.argv  
     [/home/fperez/usr/bin/ipython]
 
 
 System command aliases
 ----------------------
 
 The %alias magic function and the alias option in the ipythonrc
 configuration file allow you to define magic functions which are in fact
 system shell commands. These aliases can have parameters.
 
 '%alias alias_name cmd' defines 'alias_name' as an alias for 'cmd'
 
 Then, typing '%alias_name params' will execute the system command 'cmd
 params' (from your underlying operating system).
 
 You can also define aliases with parameters using %s specifiers (one per
 parameter). The following example defines the %parts function as an
 alias to the command 'echo first %s second %s' where each %s will be
 replaced by a positional parameter to the call to %parts::
 
     In [1]: alias parts echo first %s second %s 
     In [2]: %parts A B 
     first A second B  
     In [3]: %parts A  
     Incorrect number of arguments: 2 expected.  
     parts is an alias to: 'echo first %s second %s'
 
 If called with no parameters, %alias prints the table of currently
 defined aliases.
 
 The %rehash/rehashx magics allow you to load your entire $PATH as
 ipython aliases. See their respective docstrings (or sec. 6.2
 <#sec:magic> for further details).
 
 
 .. _dreload:
 
 Recursive reload
 ----------------
 
 The dreload function does a recursive reload of a module: changes made
 to the module since you imported will actually be available without
 having to exit.
 
 
 Verbose and colored exception traceback printouts
 -------------------------------------------------
 
 IPython provides the option to see very detailed exception tracebacks,
 which can be especially useful when debugging large programs. You can
 run any Python file with the %run function to benefit from these
 detailed tracebacks. Furthermore, both normal and verbose tracebacks can
 be colored (if your terminal supports it) which makes them much easier
 to parse visually.
 
 See the magic xmode and colors functions for details (just type %magic).
 
 These features are basically a terminal version of Ka-Ping Yee's cgitb
 module, now part of the standard Python library.
 
 
 .. _input_caching:
 
 Input caching system
 --------------------
 
 IPython offers numbered prompts (In/Out) with input and output caching
 (also referred to as 'input history'). All input is saved and can be 
 retrieved as variables (besides the usual arrow key recall), in 
 addition to the %rep magic command that brings a history entry
 up for editing on the next  command line.
 
 The following GLOBAL variables always exist (so don't overwrite them!):
 _i: stores previous input. _ii: next previous. _iii: next-next previous.
 _ih : a list of all input _ih[n] is the input from line n and this list
 is aliased to the global variable In. If you overwrite In with a
 variable of your own, you can remake the assignment to the internal list
 with a simple 'In=_ih'.
 
 Additionally, global variables named _i<n> are dynamically created (<n>
 being the prompt counter), such that
 _i<n> == _ih[<n>] == In[<n>].
 
 For example, what you typed at prompt 14 is available as _i14, _ih[14]
 and In[14].
 
 This allows you to easily cut and paste multi line interactive prompts
 by printing them out: they print like a clean string, without prompt
 characters. You can also manipulate them like regular variables (they
 are strings), modify or exec them (typing 'exec _i9' will re-execute the
 contents of input prompt 9, 'exec In[9:14]+In[18]' will re-execute lines
 9 through 13 and line 18).
 
 You can also re-execute multiple lines of input easily by using the
 magic %macro function (which automates the process and allows
 re-execution without having to type 'exec' every time). The macro system
 also allows you to re-execute previous lines which include magic
 function calls (which require special processing). Type %macro? or see
 sec. 6.2 <#sec:magic> for more details on the macro system.
 
 A history function %hist allows you to see any part of your input
 history by printing a range of the _i variables.
 
 You can also search ('grep') through your history by typing 
 '%hist -g somestring'. This also searches through the so called *shadow history*,
 which remembers all the commands (apart from multiline code blocks)
 you have ever entered. Handy for searching for svn/bzr URL's, IP adrresses
 etc. You can bring shadow history entries listed by '%hist -g' up for editing 
 (or re-execution by just pressing ENTER) with %rep command. Shadow history 
 entries are not available as _iNUMBER variables, and they are identified by 
 the '0' prefix in %hist -g output. That is, history entry 12 is a normal 
 history entry, but 0231 is a shadow history entry.
 
 Shadow history was added because the readline history is inherently very
 unsafe - if you have multiple IPython sessions open, the last session 
 to close will overwrite the history of previountly closed session. Likewise,
 if a crash occurs, history is never saved, whereas shadow history entries
 are added after entering every command (so a command executed 
 in another IPython session is immediately available in other IPython 
 sessions that are open).
 
 To conserve space, a command can exist in shadow history only once - it doesn't 
 make sense to store a common line like "cd .." a thousand times. The idea is 
 mainly to provide a reliable place where valuable, hard-to-remember commands can 
 always be retrieved, as opposed to providing an exact sequence of commands
 you have entered in actual order.
 
 Because shadow history has all the commands you have ever executed,
 time taken by %hist -g will increase oven time. If it ever starts to take
 too long (or it ends up containing sensitive information like passwords), 
 clear the shadow history by `%clear shadow_nuke`.
 
 Time taken to add entries to shadow history should be negligible, but 
 in any case, if you start noticing performance degradation after using 
 IPython for a long time (or running a script that floods the shadow history!), 
 you can 'compress' the shadow history by executing 
 `%clear shadow_compress`. In practice, this should never be necessary
 in normal use.
 
 .. _output_caching:
 
 Output caching system
 ---------------------
 
 For output that is returned from actions, a system similar to the input
 cache exists but using _ instead of _i. Only actions that produce a
 result (NOT assignments, for example) are cached. If you are familiar
 with Mathematica, IPython's _ variables behave exactly like
 Mathematica's % variables.
 
 The following GLOBAL variables always exist (so don't overwrite them!):
 
     * [_] (a single underscore) : stores previous output, like Python's
       default interpreter.
     * [__] (two underscores): next previous.
     * [___] (three underscores): next-next previous.
 
 Additionally, global variables named _<n> are dynamically created (<n>
 being the prompt counter), such that the result of output <n> is always
 available as _<n> (don't use the angle brackets, just the number, e.g.
 _21).
 
 These global variables are all stored in a global dictionary (not a
 list, since it only has entries for lines which returned a result)
 available under the names _oh and Out (similar to _ih and In). So the
 output from line 12 can be obtained as _12, Out[12] or _oh[12]. If you
 accidentally overwrite the Out variable you can recover it by typing
 'Out=_oh' at the prompt.
 
 This system obviously can potentially put heavy memory demands on your
 system, since it prevents Python's garbage collector from removing any
 previously computed results. You can control how many results are kept
 in memory with the option (at the command line or in your ipythonrc
 file) cache_size. If you set it to 0, the whole system is completely
 disabled and the prompts revert to the classic '>>>' of normal Python.
 
 
 Directory history
 -----------------
 
 Your history of visited directories is kept in the global list _dh, and
 the magic %cd command can be used to go to any entry in that list. The
 %dhist command allows you to view this history. Do ``cd -<TAB`` to
 conventiently view the directory history.
 
 
 Automatic parentheses and quotes
 --------------------------------
 
 These features were adapted from Nathan Gray's LazyPython. They are
 meant to allow less typing for common situations.
 
 
 Automatic parentheses
 ---------------------
 
 Callable objects (i.e. functions, methods, etc) can be invoked like this
 (notice the commas between the arguments)::
 
     >>> callable_ob arg1, arg2, arg3
 
 and the input will be translated to this::
 
     -> callable_ob(arg1, arg2, arg3)
 
 You can force automatic parentheses by using '/' as the first character
 of a line. For example::
 
     >>> /globals # becomes 'globals()'
 
 Note that the '/' MUST be the first character on the line! This won't work::
 
     >>> print /globals # syntax error
 
 In most cases the automatic algorithm should work, so you should rarely
 need to explicitly invoke /. One notable exception is if you are trying
 to call a function with a list of tuples as arguments (the parenthesis
 will confuse IPython)::
 
     In [1]: zip (1,2,3),(4,5,6) # won't work
 
 but this will work::
 
     In [2]: /zip (1,2,3),(4,5,6) 
     ---> zip ((1,2,3),(4,5,6))  
     Out[2]= [(1, 4), (2, 5), (3, 6)]
 
 IPython tells you that it has altered your command line by displaying
 the new command line preceded by ->. e.g.::
 
     In [18]: callable list 
     ----> callable (list)
 
 
 Automatic quoting
 -----------------
 
 You can force automatic quoting of a function's arguments by using ','
 or ';' as the first character of a line. For example::
 
     >>> ,my_function /home/me # becomes my_function("/home/me")
 
 If you use ';' instead, the whole argument is quoted as a single string
 (while ',' splits on whitespace)::
 
     >>> ,my_function a b c # becomes my_function("a","b","c")
 
     >>> ;my_function a b c # becomes my_function("a b c")
 
 Note that the ',' or ';' MUST be the first character on the line! This
 won't work::
 
     >>> x = ,my_function /home/me # syntax error
 
 IPython as your default Python environment
 ==========================================
 
 Python honors the environment variable PYTHONSTARTUP and will execute at
 startup the file referenced by this variable. If you put at the end of
 this file the following two lines of code::
 
     import IPython 
     IPython.Shell.IPShell().mainloop(sys_exit=1)
 
 then IPython will be your working environment anytime you start Python.
 The sys_exit=1 is needed to have IPython issue a call to sys.exit() when
 it finishes, otherwise you'll be back at the normal Python '>>>'
 prompt.
 
 This is probably useful to developers who manage multiple Python
 versions and don't want to have correspondingly multiple IPython
 versions. Note that in this mode, there is no way to pass IPython any
 command-line options, as those are trapped first by Python itself.
 
 .. _Embedding:
 
 Embedding IPython
 =================
 
 It is possible to start an IPython instance inside your own Python
 programs. This allows you to evaluate dynamically the state of your
 code, operate with your variables, analyze them, etc. Note however that
 any changes you make to values while in the shell do not propagate back
 to the running code, so it is safe to modify your values because you
 won't break your code in bizarre ways by doing so.
 
 This feature allows you to easily have a fully functional python
 environment for doing object introspection anywhere in your code with a
 simple function call. In some cases a simple print statement is enough,
 but if you need to do more detailed analysis of a code fragment this
 feature can be very valuable.
 
 It can also be useful in scientific computing situations where it is
 common to need to do some automatic, computationally intensive part and
 then stop to look at data, plots, etc.
 Opening an IPython instance will give you full access to your data and
 functions, and you can resume program execution once you are done with
 the interactive part (perhaps to stop again later, as many times as
 needed).
 
 The following code snippet is the bare minimum you need to include in
 your Python programs for this to work (detailed examples follow later)::
 
     from IPython.Shell import IPShellEmbed
 
     ipshell = IPShellEmbed()
 
     ipshell() # this call anywhere in your program will start IPython
 
 You can run embedded instances even in code which is itself being run at
 the IPython interactive prompt with '%run <filename>'. Since it's easy
 to get lost as to where you are (in your top-level IPython or in your
 embedded one), it's a good idea in such cases to set the in/out prompts
 to something different for the embedded instances. The code examples
 below illustrate this.
 
 You can also have multiple IPython instances in your program and open
 them separately, for example with different options for data
 presentation. If you close and open the same instance multiple times,
 its prompt counters simply continue from each execution to the next.
 
 Please look at the docstrings in the Shell.py module for more details on
 the use of this system.
 
 The following sample file illustrating how to use the embedding
 functionality is provided in the examples directory as example-embed.py.
 It should be fairly self-explanatory::
 
 
     #!/usr/bin/env python
 
     """An example of how to embed an IPython shell into a running program.
 
     Please see the documentation in the IPython.Shell module for more details.
 
     The accompanying file example-embed-short.py has quick code fragments for
     embedding which you can cut and paste in your code once you understand how
     things work.
 
     The code in this file is deliberately extra-verbose, meant for learning."""
 
     # The basics to get you going:
 
     # IPython sets the __IPYTHON__ variable so you can know if you have nested
     # copies running.
 
     # Try running this code both at the command line and from inside IPython (with
     # %run example-embed.py)
     try:
         __IPYTHON__
     except NameError:
         nested = 0
         args = ['']
     else:
         print "Running nested copies of IPython."
         print "The prompts for the nested copy have been modified"
         nested = 1
         # what the embedded instance will see as sys.argv:
         args = ['-pi1','In <\\#>: ','-pi2','   .\\D.: ',
                 '-po','Out<\\#>: ','-nosep']
 
     # First import the embeddable shell class
     from IPython.Shell import IPShellEmbed
 
     # Now create an instance of the embeddable shell. The first argument is a
     # string with options exactly as you would type them if you were starting
     # IPython at the system command line. Any parameters you want to define for
     # configuration can thus be specified here.
     ipshell = IPShellEmbed(args,
                            banner = 'Dropping into IPython',
                            exit_msg = 'Leaving Interpreter, back to program.')
 
     # Make a second instance, you can have as many as you want.
     if nested:
         args[1] = 'In2<\\#>'
     else:
         args = ['-pi1','In2<\\#>: ','-pi2','   .\\D.: ',
                 '-po','Out<\\#>: ','-nosep']
     ipshell2 = IPShellEmbed(args,banner = 'Second IPython instance.')
 
     print '\nHello. This is printed from the main controller program.\n'
 
     # You can then call ipshell() anywhere you need it (with an optional
     # message):
     ipshell('***Called from top level. '
             'Hit Ctrl-D to exit interpreter and continue program.\n'
             'Note that if you use %kill_embedded, you can fully deactivate\n'
             'This embedded instance so it will never turn on again')
 
     print '\nBack in caller program, moving along...\n'
 
     #---------------------------------------------------------------------------
     # More details:
 
     # IPShellEmbed instances don't print the standard system banner and
     # messages. The IPython banner (which actually may contain initialization
     # messages) is available as <instance>.IP.BANNER in case you want it.
 
     # IPShellEmbed instances print the following information everytime they
     # start:
 
     # - A global startup banner.
 
     # - A call-specific header string, which you can use to indicate where in the
     # execution flow the shell is starting.
 
     # They also print an exit message every time they exit.
 
     # Both the startup banner and the exit message default to None, and can be set
     # either at the instance constructor or at any other time with the
     # set_banner() and set_exit_msg() methods.
 
     # The shell instance can be also put in 'dummy' mode globally or on a per-call
     # basis. This gives you fine control for debugging without having to change
     # code all over the place.
 
     # The code below illustrates all this.
 
 
     # This is how the global banner and exit_msg can be reset at any point
     ipshell.set_banner('Entering interpreter - New Banner')
     ipshell.set_exit_msg('Leaving interpreter - New exit_msg')
 
     def foo(m):
         s = 'spam'
         ipshell('***In foo(). Try @whos, or print s or m:')
         print 'foo says m = ',m
 
     def bar(n):
         s = 'eggs'
         ipshell('***In bar(). Try @whos, or print s or n:')
         print 'bar says n = ',n
 
     # Some calls to the above functions which will trigger IPython:
     print 'Main program calling foo("eggs")\n'
     foo('eggs')
 
     # The shell can be put in 'dummy' mode where calls to it silently return. This
     # allows you, for example, to globally turn off debugging for a program with a
     # single call.
     ipshell.set_dummy_mode(1)
     print '\nTrying to call IPython which is now "dummy":'
     ipshell()
     print 'Nothing happened...'
     # The global 'dummy' mode can still be overridden for a single call
     print '\nOverriding dummy mode manually:'
     ipshell(dummy=0)
 
     # Reactivate the IPython shell
     ipshell.set_dummy_mode(0)
 
     print 'You can even have multiple embedded instances:'
     ipshell2()
 
     print '\nMain program calling bar("spam")\n'
     bar('spam')
 
     print 'Main program finished. Bye!'
 
     #********************** End of file <example-embed.py> ***********************
 
 Once you understand how the system functions, you can use the following
 code fragments in your programs which are ready for cut and paste::
 
 
     """Quick code snippets for embedding IPython into other programs.
 
     See example-embed.py for full details, this file has the bare minimum code for
     cut and paste use once you understand how to use the system."""
 
     #---------------------------------------------------------------------------
     # This code loads IPython but modifies a few things if it detects it's running
     # embedded in another IPython session (helps avoid confusion)
 
     try:
         __IPYTHON__
     except NameError:
         argv = ['']
         banner = exit_msg = ''
     else:
         # Command-line options for IPython (a list like sys.argv)
         argv = ['-pi1','In <\\#>:','-pi2','   .\\D.:','-po','Out<\\#>:']
         banner = '*** Nested interpreter ***'
         exit_msg = '*** Back in main IPython ***'
 
     # First import the embeddable shell class
     from IPython.Shell import IPShellEmbed
     # Now create the IPython shell instance. Put ipshell() anywhere in your code
     # where you want it to open.
     ipshell = IPShellEmbed(argv,banner=banner,exit_msg=exit_msg)
 
     #---------------------------------------------------------------------------
     # This code will load an embeddable IPython shell always with no changes for
     # nested embededings.
 
     from IPython.Shell import IPShellEmbed
     ipshell = IPShellEmbed()
     # Now ipshell() will open IPython anywhere in the code.
 
     #---------------------------------------------------------------------------
     # This code loads an embeddable shell only if NOT running inside
     # IPython. Inside IPython, the embeddable shell variable ipshell is just a
     # dummy function.
 
     try:
         __IPYTHON__
     except NameError:
         from IPython.Shell import IPShellEmbed
         ipshell = IPShellEmbed()
         # Now ipshell() will open IPython anywhere in the code
     else:
         # Define a dummy ipshell() so the same code doesn't crash inside an
         # interactive IPython
         def ipshell(): pass
 
     #******************* End of file <example-embed-short.py> ********************
 
 Using the Python debugger (pdb)
 ===============================
 
 Running entire programs via pdb
 -------------------------------
 
 pdb, the Python debugger, is a powerful interactive debugger which
 allows you to step through code, set breakpoints, watch variables,
 etc.  IPython makes it very easy to start any script under the control
 of pdb, regardless of whether you have wrapped it into a 'main()'
 function or not. For this, simply type '%run -d myscript' at an
 IPython prompt. See the %run command's documentation (via '%run?' or
 in Sec. magic_ for more details, including how to control where pdb
 will stop execution first.
 
 For more information on the use of the pdb debugger, read the included
 pdb.doc file (part of the standard Python distribution). On a stock
 Linux system it is located at /usr/lib/python2.3/pdb.doc, but the
 easiest way to read it is by using the help() function of the pdb module
 as follows (in an IPython prompt):
 
 In [1]: import pdb 
 In [2]: pdb.help()
 
 This will load the pdb.doc document in a file viewer for you automatically.
 
 
 Automatic invocation of pdb on exceptions
 -----------------------------------------
 
 IPython, if started with the -pdb option (or if the option is set in
 your rc file) can call the Python pdb debugger every time your code
 triggers an uncaught exception. This feature
 can also be toggled at any time with the %pdb magic command. This can be
 extremely useful in order to find the origin of subtle bugs, because pdb
 opens up at the point in your code which triggered the exception, and
 while your program is at this point 'dead', all the data is still
 available and you can walk up and down the stack frame and understand
 the origin of the problem.
 
 Furthermore, you can use these debugging facilities both with the
 embedded IPython mode and without IPython at all. For an embedded shell
 (see sec. Embedding_), simply call the constructor with
 '-pdb' in the argument string and automatically pdb will be called if an
 uncaught exception is triggered by your code.
 
 For stand-alone use of the feature in your programs which do not use
 IPython at all, put the following lines toward the top of your 'main'
 routine::
 
     import sys
     from IPython.core import ultratb
     sys.excepthook = ultratb.FormattedTB(mode='Verbose',
     color_scheme='Linux', call_pdb=1)
 
 The mode keyword can be either 'Verbose' or 'Plain', giving either very
 detailed or normal tracebacks respectively. The color_scheme keyword can
 be one of 'NoColor', 'Linux' (default) or 'LightBG'. These are the same
 options which can be set in IPython with -colors and -xmode.
 
 This will give any of your programs detailed, colored tracebacks with
 automatic invocation of pdb.
 
 
 Extensions for syntax processing
 ================================
 
 This isn't for the faint of heart, because the potential for breaking
 things is quite high. But it can be a very powerful and useful feature.
 In a nutshell, you can redefine the way IPython processes the user input
 line to accept new, special extensions to the syntax without needing to
 change any of IPython's own code.
 
 In the IPython/extensions directory you will find some examples
 supplied, which we will briefly describe now. These can be used 'as is'
 (and both provide very useful functionality), or you can use them as a
 starting point for writing your own extensions.
 
 
 Pasting of code starting with '>>> ' or '... '
 ----------------------------------------------
 
 In the python tutorial it is common to find code examples which have
 been taken from real python sessions. The problem with those is that all
 the lines begin with either '>>> ' or '... ', which makes it impossible
 to paste them all at once. One must instead do a line by line manual
 copying, carefully removing the leading extraneous characters.
 
 This extension identifies those starting characters and removes them
 from the input automatically, so that one can paste multi-line examples
 directly into IPython, saving a lot of time. Please look at the file
 InterpreterPasteInput.py in the IPython/extensions directory for details
 on how this is done.
 
 IPython comes with a special profile enabling this feature, called
 tutorial. Simply start IPython via 'ipython -p tutorial' and the feature
 will be available. In a normal IPython session you can activate the
 feature by importing the corresponding module with:
 In [1]: import IPython.extensions.InterpreterPasteInput
 
 The following is a 'screenshot' of how things work when this extension
 is on, copying an example from the standard tutorial::
 
     IPython profile: tutorial 
 
     *** Pasting of code with ">>>" or "..." has been enabled. 
 
     In [1]: >>> def fib2(n): # return Fibonacci series up to n 
        ...: ...     """Return a list containing the Fibonacci series up to
     n.""" 
        ...: ...     result = [] 
        ...: ...     a, b = 0, 1 
        ...: ...     while b < n: 
        ...: ...         result.append(b)    # see below 
        ...: ...         a, b = b, a+b 
        ...: ...     return result 
        ...: 
 
     In [2]: fib2(10) 
     Out[2]: [1, 1, 2, 3, 5, 8]
 
 Note that as currently written, this extension does not recognize
 IPython's prompts for pasting. Those are more complicated, since the
 user can change them very easily, they involve numbers and can vary in
 length. One could however extract all the relevant information from the
 IPython instance and build an appropriate regular expression. This is
 left as an exercise for the reader.
 
 
 Input of physical quantities with units
 ---------------------------------------
 
 The module PhysicalQInput allows a simplified form of input for physical
 quantities with units. This file is meant to be used in conjunction with
 the PhysicalQInteractive module (in the same directory) and
 Physics.PhysicalQuantities from Konrad Hinsen's ScientificPython
 (http://dirac.cnrs-orleans.fr/ScientificPython/).
 
 The Physics.PhysicalQuantities module defines PhysicalQuantity objects,
 but these must be declared as instances of a class. For example, to
 define v as a velocity of 3 m/s, normally you would write::
 
     In [1]: v = PhysicalQuantity(3,'m/s')
 
 Using the PhysicalQ_Input extension this can be input instead as: 
 In [1]: v = 3 m/s
 which is much more convenient for interactive use (even though it is
 blatantly invalid Python syntax).
 
 The physics profile supplied with IPython (enabled via 'ipython -p
 physics') uses these extensions, which you can also activate with:
 
 from math import * # math MUST be imported BEFORE PhysicalQInteractive 
 from IPython.extensions.PhysicalQInteractive import * 
 import IPython.extensions.PhysicalQInput
 
 .. _gui_support:
 
 GUI event loop support support
 ==============================
 
 .. versionadded:: 0.11
     The ``%gui`` magic and :mod:`IPython.lib.inputhook`.
 
 IPython has excellent support for working interactively with Graphical User
 Interface (GUI) toolkits, such as wxPython, PyQt4, PyGTK and Tk. This is
 implemented using Python's builtin ``PyOSInputHook`` hook. This implementation
 is extremely robust compared to our previous threaded based version. The
 advantages of
 
 * GUIs can be enabled and disabled dynamically at runtime.
 * The active GUI can be switched dynamically at runtime.
 * In some cases, multiple GUIs can run simultaneously with no problems.
 * There is a developer API in :mod:`IPython.lib.inputhook` for customizing 
   all of these things.
 
 For users, enabling GUI event loop integration is simple.  You simple use the
 ``%gui`` magic as follows::
 
     %gui [-a] [GUINAME]
 
 With no arguments, ``%gui`` removes all GUI support.  Valid ``GUINAME``
 arguments are ``wx``, ``qt4``, ``gtk`` and ``tk``.  The ``-a`` option will
 create and return a running application object for the selected GUI toolkit.
 
 This to use wxPython interactively and create a running :class:`wx.App`
 object, do::
 
     %gui -a wx
 
 For information on IPython's Matplotlib integration (and the ``pylab`` mode)
 see :ref:`this section <matplotlib_support>`.
 
 For developers that want to use IPython's GUI event loop integration in
 the form of a library, the capabilities are exposed in library form
 in the :mod:`IPython.lib.inputhook`.  Interested developers should see the
 module docstrings for more information.
 
+In addition, we also have a number of examples in our source directory
+:file:`docs/examples/lib` that demonstrate these capabilities.
+
 .. _matplotlib_support:
 
 Plotting with matplotlib
 ========================
 
 
 `Matplotlib`_ provides high quality 2D and
 3D plotting for Python. Matplotlib can produce plots on screen using a variety
 of GUI toolkits, including Tk, PyGTK, PyQt4 and wxPython. It also provides a
 number of commands useful for scientific computing, all with a syntax
 compatible with that of the popular Matlab program.
 
 Many IPython users have come to rely on IPython's ``-pylab`` mode which
 automates the integration of Matplotlib with IPython. We are still in the
 process of working with the Matplotlib developers to finalize the new pylab
 API, but for now you can use Matplotlib interactively using the following
 commands::
 
     %gui -a wx
     import matplotlib
     matplotlib.use('wxagg')
     from matplotlib import pylab
     pylab.interactive(True)
 
 All of this will soon be automated as Matplotlib beings to include
 new logic that uses our new GUI support.
 
 .. _interactive_demos:
 
 Interactive demos with IPython
 ==============================
 
 IPython ships with a basic system for running scripts interactively in
 sections, useful when presenting code to audiences. A few tags embedded
 in comments (so that the script remains valid Python code) divide a file
 into separate blocks, and the demo can be run one block at a time, with
 IPython printing (with syntax highlighting) the block before executing
 it, and returning to the interactive prompt after each block. The
 interactive namespace is updated after each block is run with the
 contents of the demo's namespace.
 
 This allows you to show a piece of code, run it and then execute
 interactively commands based on the variables just created. Once you
 want to continue, you simply execute the next block of the demo. The
 following listing shows the markup necessary for dividing a script into
 sections for execution as a demo::
 
 
     """A simple interactive demo to illustrate the use of IPython's Demo class.
 
     Any python script can be run as a demo, but that does little more than showing
     it on-screen, syntax-highlighted in one shot.  If you add a little simple
     markup, you can stop at specified intervals and return to the ipython prompt,
     resuming execution later.
     """
 
     print 'Hello, welcome to an interactive IPython demo.'
     print 'Executing this block should require confirmation before proceeding,'
     print 'unless auto_all has been set to true in the demo object'
 
     # The mark below defines a block boundary, which is a point where IPython will
     # stop execution and return to the interactive prompt.
     # Note that in actual interactive execution, 
     # <demo> --- stop ---
 
     x = 1
     y = 2
 
     # <demo> --- stop ---
 
     # the mark below makes this block as silent
     # <demo> silent
 
     print 'This is a silent block, which gets executed but not printed.'
 
     # <demo> --- stop ---
     # <demo> auto
     print 'This is an automatic block.'
     print 'It is executed without asking for confirmation, but printed.'
     z = x+y
 
     print 'z=',x
 
     # <demo> --- stop ---
     # This is just another normal block.
     print 'z is now:', z
 
     print 'bye!'
 
 In order to run a file as a demo, you must first make a Demo object out
 of it. If the file is named myscript.py, the following code will make a
 demo::
 
     from IPython.demo import Demo
 
     mydemo = Demo('myscript.py')
 
 This creates the mydemo object, whose blocks you run one at a time by
 simply calling the object with no arguments. If you have autocall active
 in IPython (the default), all you need to do is type::
 
     mydemo 
 
 and IPython will call it, executing each block. Demo objects can be
 restarted, you can move forward or back skipping blocks, re-execute the
 last block, etc. Simply use the Tab key on a demo object to see its
 methods, and call '?' on them to see their docstrings for more usage
 details. In addition, the demo module itself contains a comprehensive
 docstring, which you can access via::
 
     from IPython import demo
 
     demo?
 
 Limitations: It is important to note that these demos are limited to
 fairly simple uses. In particular, you can not put division marks in
 indented code (loops, if statements, function definitions, etc.)
 Supporting something like this would basically require tracking the
 internal execution state of the Python interpreter, so only top-level
 divisions are allowed. If you want to be able to open an IPython
 instance at an arbitrary point in a program, you can use IPython's
 embedding facilities, described in detail in Sec. 9
 
 .. [Matplotlib] Matplotlib. http://matplotlib.sourceforge.net