Fix bug where post-execute code was being called twice.

IPython/core/interactiveshell.py

@@ -2122,7 +2122,7 b' class InteractiveShell(Configurable, Magic):'
         # This seems like a reasonable usability design.
         last = blocks[-1]
         if len(last.splitlines()) < 2:
-            self.runcode(''.join(blocks[:-1]))
+            self.runcode(''.join(blocks[:-1]), post_execute=False)
             self.runlines(last)
         else:
             self.runcode(cell)
@@ -2232,7 +2232,7 b' class InteractiveShell(Configurable, Magic):'
         else:
             return None
 
-    def runcode(self, code_obj):
+    def runcode(self, code_obj, post_execute=True):
         """Execute a code object.
 
         When an exception occurs, self.showtraceback() is called to display a
@@ -2284,15 +2284,17 b' class InteractiveShell(Configurable, Magic):'
         # are reported only minimally and just on the terminal, because the
         # main exception channel may be occupied with a user traceback.
         # FIXME: we need to think this mechanism a little more carefully.
-        for func in self._post_execute:
-            try:
-                func()
-            except:
-                head = '[ ERROR ] Evaluating post_execute function: %s' % func
-                print >> io.Term.cout, head
-                print >> io.Term.cout, self._simple_error()
-                print >> io.Term.cout, 'Removing from post_execute'
-                self._post_execute.remove(func)
+        if post_execute:
+            for func in self._post_execute:
+                try:
+                    func()
+                except:
+                    head = '[ ERROR ] Evaluating post_execute function: %s' % \
+                           func
+                    print >> io.Term.cout, head
+                    print >> io.Term.cout, self._simple_error()
+                    print >> io.Term.cout, 'Removing from post_execute'
+                    self._post_execute.remove(func)
 
         # Flush out code object which has been run (and source)
         self.code_to_run = None