Minor improvements to how namespaces are handled.

IPython/core/displayhook.py

@@ -265,16 +265,16 b' class DisplayHook(Configurable):'
                 self.___ = self.__
                 self.__ = self._
                 self._ = result
-                self.shell.user_ns.update({'_':self._,
-                                           '__':self.__,
-                                           '___':self.___})
+                self.shell.push({'_':self._,
+                                 '__':self.__,
+                                '___':self.___}, interactive=False)
 
             # hackish access to top-level  namespace to create _1,_2... dynamically
             to_main = {}
             if self.do_full_cache:
                 new_result = '_'+`self.prompt_count`
                 to_main[new_result] = result
-                self.shell.user_ns.update(to_main)
+                self.shell.push(to_main, interactive=False)
                 self.shell.user_ns['_oh'][self.prompt_count] = result
 
     def log_output(self, format_dict):

IPython/core/history.py

@@ -559,7 +559,8 b' class HistoryManager(HistoryAccessor):'
                    '_ii': self._ii,
                    '_iii': self._iii,
                    new_i : self._i00 }
-        self.shell.user_ns.update(to_main)
+
+        self.shell.push(to_main, interactive=False)
 
     def store_output(self, line_num):
         """If database output logging is enabled, this saves all the

IPython/core/interactiveshell.py

@@ -1073,6 +1073,16 b' class InteractiveShell(SingletonConfigurable, Magic):'
 
         # Finally, update the real user's namespace
         self.user_ns.update(ns)
+    
+    @property
+    def all_ns_refs(self):
+        """Get a list of references to all the namespace dictionaries in which
+        IPython might store a user-created object.
+        
+        Note that this does not include the displayhook, which also caches
+        objects from the output."""
+        return [self.user_ns, self.user_global_ns,
+                self._user_main_module.__dict__] + self._main_ns_cache.values()
 
     def reset(self, new_session=True):
         """Clear all internal namespaces, and attempt to release references to
@@ -1103,6 +1113,8 b' class InteractiveShell(SingletonConfigurable, Magic):'
         for k in drop_keys:
             del ns[k]
         
+        self.user_ns_hidden.clear()
+        
         # Restore the user namespaces to minimal usability
         self.init_user_ns()
 
@@ -1133,8 +1145,7 b' class InteractiveShell(SingletonConfigurable, Magic):'
         if varname in ('__builtin__', '__builtins__'):
             raise ValueError("Refusing to delete %s" % varname)
 
-        ns_refs = [self.user_ns, self.user_global_ns,
-                self._user_main_module.__dict__] + self._main_ns_cache.values()
+        ns_refs = self.all_ns_refs
         
         if by_name:                    # Delete by name
             for ns in ns_refs:
@@ -1176,7 +1187,7 b' class InteractiveShell(SingletonConfigurable, Magic):'
                 raise TypeError('regex must be a string or compiled pattern')
             # Search for keys in each namespace that match the given regex
             # If a match is found, delete the key/value pair.
-            for ns in [self.user_ns, self.user_global_ns]:
+            for ns in self.all_ns_refs:
                 for var in ns:
                     if m.search(var):
                         del ns[var]
@@ -1224,11 +1235,9 b' class InteractiveShell(SingletonConfigurable, Magic):'
         # And configure interactive visibility
         user_ns_hidden = self.user_ns_hidden
         if interactive:
-            for name in vdict:
-                user_ns_hidden.discard(name)
+            user_ns_hidden.difference_update(vdict)
         else:
-            for name in vdict:
-                user_ns_hidden.add(name)
+            user_ns_hidden.update(vdict)
     
     def drop_by_id(self, variables):
         """Remove a dict of variables from the user namespace, if they are the

IPython/core/tests/test_iplib.py

@@ -30,9 +30,6 b' ip = get_ipython()'
 
 def test_reset():
     """reset must clear most namespaces."""
-    # The number of variables in the private user_ns_hidden is not zero, but it
-    # should be constant regardless of what we do
-    nvars_hidden = len(ip.user_ns_hidden)
 
     # Check that reset runs without error
     ip.reset()
@@ -40,6 +37,7 b' def test_reset():'
     # Once we've reset it (to clear of any junk that might have been there from
     # other tests, we can count how many variables are in the user's namespace
     nvars_user_ns = len(ip.user_ns)
+    nvars_hidden = len(ip.user_ns_hidden)
 
     # Now add a few variables to user_ns, and check that reset clears them
     ip.user_ns['x'] = 1