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

@@ -237,14 +237,20 b' class Component(HasTraitlets):'
             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()
@@ -315,7 +321,10 b' class Component(HasTraitlets):'
                     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):

docs/examples/kernel/wordfreq.py

@@ -25,7 +25,7 b' def print_wordfreq(freqs, n=10):'
         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 = {}
@@ -37,7 +37,7 b' def wordfreq_to_weightsize(worddict, minsize=10, maxsize=50, minalpha=0.4, maxal'
     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
 
@@ -55,10 +55,10 b' def tagcloud(worddict, n=10, minsize=10, maxsize=50, minalpha=0.4, maxalpha=1.0)'
     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