Work on examples and fixed a super subtle bug in Component.

* Recently, we stopped copying the config passed to a Component. This
  had a subtle side effect that mutable config attribute values were
  becoming class wide attributes. We are now doing a deep copy of all
  attributes as they are set on the Component instance.

IPython/core/component.py

@@ -1,337 +1,346 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.importstring import import_item
 from IPython.config.loader import Config
 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 a 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 = cls.__new__(cls, *args, **kw)
 
         # Register the instance before __init__ is called so get_instances 
         # works inside __init__ methods!
         indices = cls.register_instance(instance)
 
         # This is in a try/except because of the __init__ method fails, the
         # instance is discarded and shouldn't be tracked.
         try:
             if isinstance(instance, cls):
                 cls.__init__(instance, *args, **kw)
         except:
             # Unregister the instance because __init__ failed!
             cls.unregister_instances(indices)
             raise
         else:
             return instance
 
     def register_instance(cls, instance):
         """Register instance with cls and its subclasses."""
         # indices is a list of the keys used to register the instance
         # with.  This list is needed if the instance needs to be unregistered.
         indices = []
         for c in cls.__mro__:
             if issubclass(cls, c) and issubclass(c, Component):
                 c.__numcreated += 1
                 indices.append(c.__numcreated)
                 c.__instance_refs[c.__numcreated] = instance
             else:
                 break
         return indices
 
     def unregister_instances(cls, indices):
         """Unregister instance with cls and its subclasses."""
         for c, index in zip(cls.__mro__, indices):
             try:
                 del c.__instance_refs[index]
             except KeyError:
                 pass
 
     def clear_instances(cls):
         """Clear all instances tracked by cls."""
         cls.__instance_refs.clear()
         cls.__numcreated = 0
 
     def get_instances(cls, name=None, root=None, klass=None):
         """Get all instances of cls and its subclasses.
 
         Parameters
         ----------
         name : str
             Limit to components with this name.
         root : Component or subclass
             Limit to components having this root.
         klass : class or str
             Limits to instances of the class or its subclasses.  If a str
             is given ut must be in the form 'foo.bar.MyClass'.  The str
             form of this argument is useful for forward declarations.
         """
         if klass is not None:
             if isinstance(klass, basestring):
                 klass = import_item(klass)
             # Limit search to instances of klass for performance
             if issubclass(klass, Component):
                 return klass.get_instances(name=name, root=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, root=None,
                                    klass=None):
         """Get all instances of cls, i such that call(i)==True.
 
         This also takes the ``name`` and ``root`` and ``classname`` 
         arguments of :meth:`get_instance`
         """
         return [i for i in cls.get_instances(name, root, klass) if call(i)]
 
 
 def masquerade_as(instance, cls):
     """Let instance masquerade as an instance of cls.
 
     Sometimes, such as in testing code, it is useful to let a class
     masquerade as another.  Python, being duck typed, allows this by 
     default.  But, instances of components are tracked by their class type.
 
     After calling this, ``cls.get_instances()`` will return ``instance``. This
     does not, however, cause ``isinstance(instance, cls)`` to return ``True``.
 
     Parameters
     ----------
     instance : an instance of a Component or Component subclass
         The instance that will pretend to be a cls.
     cls : subclass of Component
         The Component subclass that instance will pretend to be.
     """
     cls.register_instance(instance)
 
 
 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(Config,(),{})
     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 : Config
             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 = config
             # We used to deepcopy, but for now we are trying to just save
             # by reference.  This *could* have side effects as all components
-            # will share config.
+            # will share config. In fact, I did find such a side effect in
+            # _config_changed below. If a config attribute value was a mutable type
+            # all instances of a component were getting the same copy, effectively
+            # making that a class attribute.
             # self.config = deepcopy(config)
         else:
             if self.parent is not None:
                 self.config = self.parent.config
                 # We used to deepcopy, but for now we are trying to just save
                 # by reference.  This *could* have side effects as all components
-                # will share config.
+                # will share config. In fact, I did find such a side effect in
+                # _config_changed below. If a config attribute value was a mutable type
+                # all instances of a component were getting the same copy, effectively
+                # making that a class attribute.
                 # 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 ``config=True`` as metadata.
 
         For any class traitlet with a ``config`` metadata attribute that is
         ``True``, we update the traitlet with the value of the corresponding
         config entry.
         """
         # Get all traitlets with a config metadata entry that is True
         traitlets = self.traitlets(config=True)
 
         # We auto-load config section for this class as well as any parent
         # classes that are Component subclasses.  This starts with Component
         # and works down the mro loading the config for each section.
         section_names = [cls.__name__ for cls in \
             reversed(self.__class__.__mro__) if 
             issubclass(cls, Component) and issubclass(self.__class__, cls)]
 
         for sname in section_names:
             # Don't do a blind getattr as that would cause the config to 
             # dynamically create the section with name self.__class__.__name__.
             if new._has_section(sname):
                 my_config = new[sname]
                 for k, v in traitlets.items():
                     # Don't allow traitlets with config=True to start with
                     # uppercase.  Otherwise, they are confused with Config
                     # subsections.  But, developers shouldn't have uppercase
                     # attributes anyways! (PEP 6)
                     if k[0].upper()==k[0] and not k.startswith('_'):
                         raise ComponentError('Component traitlets with '
                         'config=True must start with a lowercase so they are '
                         'not confused with Config subsections: %s.%s' % \
                         (self.__class__.__name__, k))
                     try:
                         # Here we grab the value from the config
                         # If k has the naming convention of a config
                         # section, it will be auto created.
                         config_value = my_config[k]
                     except KeyError:
                         pass
                     else:
                         # print "Setting %s.%s from %s.%s=%r" % \
                         #     (self.__class__.__name__,k,sname,k,config_value)
-                        setattr(self, k, config_value)
+                        # We have to do a deepcopy here if we don't deepcopy the entire
+                        # config object. If we don't, a mutable config_value will be
+                        # shared by all instances, effectively making it a class attribute.
+                        setattr(self, k, deepcopy(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 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 components."""
         if child not in self._children:
             self._children.append(child)
 
     def __repr__(self):
         return "<%s('%s')>" % (self.__class__.__name__, self.name)

docs/examples/kernel/wordfreq.py

@@ -1,66 +1,66 b''
 """Count the frequencies of words in a string"""
 
 from __future__ import division
 
 import cmath as math
 
 
 def wordfreq(text):
     """Return a dictionary of words and word counts in a string."""
 
     freqs = {}
     for word in text.split():
         lword = word.lower()
         freqs[lword] = freqs.get(lword, 0) + 1
     return freqs
 
 
 def print_wordfreq(freqs, n=10):
     """Print the n most common words and counts in the freqs dict."""
     
     words, counts = freqs.keys(), freqs.values()
     items = zip(counts, words)
     items.sort(reverse=True)
     for (count, word) in items[:n]:
         print word, count
 
 
-def wordfreq_to_weightsize(worddict, minsize=10, maxsize=50, minalpha=0.4, maxalpha=1.0):
+def wordfreq_to_weightsize(worddict, minsize=25, maxsize=50, minalpha=0.5, maxalpha=1.0):
     mincount = min(worddict.itervalues())
     maxcount = max(worddict.itervalues())
     weights = {}
     for k, v in worddict.iteritems():
         w = (v-mincount)/(maxcount-mincount)
         alpha = minalpha + (maxalpha-minalpha)*w
         size = minsize + (maxsize-minsize)*w
         weights[k] = (alpha, size)
     return weights
 
 
-def tagcloud(worddict, n=10, minsize=10, maxsize=50, minalpha=0.4, maxalpha=1.0):
+def tagcloud(worddict, n=10, minsize=25, maxsize=50, minalpha=0.5, maxalpha=1.0):
     from matplotlib import pyplot as plt
     import random
 
     worddict = wordfreq_to_weightsize(worddict, minsize, maxsize, minalpha, maxalpha)
 
     fig = plt.figure()
     ax = fig.add_subplot(111)
     ax.set_position([0.0,0.0,1.0,1.0])
     plt.xticks([])
     plt.yticks([])
 
     words = worddict.keys()
     alphas = [v[0] for v in worddict.values()]
     sizes = [v[1] for v in worddict.values()]
     items = zip(alphas, sizes, words)
     items.sort(reverse=True)
     for alpha, size, word in items[:n]:
-        xpos = random.normalvariate(0.5, 0.3)
-        ypos = random.normalvariate(0.5, 0.3)
-        # xpos = random.uniform(0.0,1.0)
-        # ypos = random.uniform(0.0,1.0)
+        # xpos = random.normalvariate(0.5, 0.3)
+        # ypos = random.normalvariate(0.5, 0.3)
+        xpos = random.uniform(0.0,1.0)
+        ypos = random.uniform(0.0,1.0)
         ax.text(xpos, ypos, word.lower(), alpha=alpha, fontsize=size)
     ax.autoscale_view()
     return ax
     
     
  No newline at end of file