Simplify logic for deciding when to auto-detect local namespace and module.

IPython/core/interactiveshell.py

@@ -881,8 +881,7 b' class InteractiveShell(SingletonConfigurable, Magic):'
     #-------------------------------------------------------------------------
     # Things related to IPython's various namespaces
     #-------------------------------------------------------------------------
-    default_user_ns = True
-    default_user_module = True
+    default_user_namespaces = True
 
     def init_create_namespaces(self, user_module=None, user_ns=None):
         # Create the namespace where the user will operate.  user_ns is
@@ -921,10 +920,8 b' class InteractiveShell(SingletonConfigurable, Magic):'
         # These routines return a properly built module and dict as needed by
         # the rest of the code, and can also be used by extension writers to
         # generate properly initialized namespaces.
-        if user_ns is not None:
-            self.default_user_ns = False
-        if user_module is not None:
-            self.default_user_module = False
+        if (user_ns is not None) or (user_module is not None):
+            self.default_user_namespaces = False
         self.user_module, self.user_ns = self.prepare_user_module(user_module, user_ns)
 
         # A record of hidden variables we have added to the user namespace, so

IPython/frontend/terminal/embed.py

@@ -172,12 +172,12 b' class InteractiveShellEmbed(TerminalInteractiveShell):'
         there is no fundamental reason why it can't work perfectly."""
 
         # Get locals and globals from caller
-        if local_ns is None or module is None:
+        if (local_ns is None or module is None) and self.default_user_namespaces:
             call_frame = sys._getframe(stack_depth).f_back
 
-            if local_ns is None and self.default_user_ns:
+            if local_ns is None:
                 local_ns = call_frame.f_locals
-            if module is None and self.default_user_module:
+            if module is None:
                 global_ns = call_frame.f_globals
                 module = sys.modules[global_ns['__name__']]