Implement a better check for hidden values for %who etc.

IPython/core/interactiveshell.py

@@ -969,7 +969,7 b' class InteractiveShell(SingletonConfigurable):'
 
         # A record of hidden variables we have added to the user namespace, so
         # we can list later only variables defined in actual interactive use.
-        self.user_ns_hidden = set()
+        self.user_ns_hidden = {}
 
         # Now that FakeModule produces a real module, we've run into a nasty
         # problem: after script execution (via %run), the module where the user
@@ -1300,7 +1300,8 b' class InteractiveShell(SingletonConfigurable):'
         # And configure interactive visibility
         user_ns_hidden = self.user_ns_hidden
         if interactive:
-            user_ns_hidden.difference_update(vdict)
+            for name in vdict:
+                user_ns_hidden.pop(name, None)
         else:
             user_ns_hidden.update(vdict)
     

IPython/core/magics/namespace.py

@@ -265,9 +265,10 b' class NamespaceMagics(Magics):'
 
         user_ns = self.shell.user_ns
         user_ns_hidden = self.shell.user_ns_hidden
+        nonmatching = object()  # This can never be in user_ns
         out = [ i for i in user_ns
                 if not i.startswith('_') \
-                and not i in user_ns_hidden ]
+                and (user_ns[i] is not user_ns_hidden.get(i, nonmatching)) ]
 
         typelist = parameter_s.split()
         if typelist: