inputhook: use '%gui none' for disabling the input hook.

IPython/lib/inputhook.py

@@ -32,6 +32,7 b" GUI_TK = 'tk'"
 GUI_OSX = 'osx'
 GUI_GLUT = 'glut'
 GUI_PYGLET = 'pyglet'
+GUI_NONE = 'none' # i.e. disable
 
 #-----------------------------------------------------------------------------
 # Utilities
@@ -417,8 +418,8 b' def enable_gui(gui=None, app=None):'
     Parameters
     ----------
     gui : optional, string or None
-      If None, clears input hook, otherwise it must be one of the recognized
-      GUI names (see ``GUI_*`` constants in module).
+      If None (or 'none'), clears input hook, otherwise it must be one
+      of the recognized GUI names (see ``GUI_*`` constants in module).
 
     app : optional, existing application object.
       For toolkits that have the concept of a global app, you can supply an
@@ -433,6 +434,7 b' def enable_gui(gui=None, app=None):'
     one.
     """
     guis = {None: clear_inputhook,
+            GUI_NONE: clear_inputhook,
             GUI_OSX: lambda app=False: None,
             GUI_TK: enable_tk,
             GUI_GTK: enable_gtk,

IPython/lib/inputhookqt4.py

@@ -90,8 +90,11 b' def create_inputhook_qt4(mgr, app=None):'
         except KeyboardInterrupt:
             got_kbdint[0] = True
             mgr.clear_inputhook()
-            print("\n(event loop interrupted - "
-                  "hit CTRL+C again to clear the prompt)")
+            print("\nKeyboardInterrupt - qt4 event loop interrupted!"
+                  "\n  * hit CTRL+C again to clear the prompt"
+                  "\n  * use '%gui none' to disable the event loop"
+                  " permanently"
+                  "\n    and '%gui qt4' to re-enable it later")
         return 0
 
     def preprompthook_qt4(ishell):