how-to use readline.set_completion_display_matches_hook()?

Stefan H. Holek stefan at
Wed Nov 7 14:14:56 CET 2012

On 07.11.2012, at 11:36, Jean-Pierre Miceli wrote:

> Hi all,
> I'm working on a tool which enable support of tab completion using the
> readline modul.
> And I have a problem with set_completion_display_matches_hook function
> I've created a display hook function and registered it. It is called
> and it prints the desire messages. But once it has completed,
> readline/python does not display the prompt.
> I've got to press the 'return' key to see the prompt again.
> What should the display hook function do to return correctly and let
> the prompt be displayed?
> Example:
> def completerHook(self, substitution, matches, longest_match_length):
>    print ""
>    print "Test of the display hook function"
>    for i in range(len(matches)):
>      print matches[i],
> I use Python 2.7.3 and done some tests on Mac OS 10.7 (Lion) and
> Ubuntu. I got the same issue on both system.

This always happens when you print newlines behind readline's back. To update the prompt area, you'd have to call rl_forced_update_display() which is AFAIK not exposed by the stdlib's readline bindings.

There is a more complete implementation of the GNU Readline APIs at With rl you can fix the prompt by calling rl.readline.redisplay(force=True) after the hook has returned.

Hope this helps,

Stefan H. Holek
stefan at

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