[Python-Dev] PyOS_InputHook and threads

[Michiel Jan Laurens de Hoon]

I have started writing a patch that replaces PyOS_InputHook with 
PyOS_AddInputHook and PyOS_RemoveInputHook. I am a bit confused though on how 
hook functions are supposed to work with threads.

PyOS_InputHook is a pointer to a hook function, which can be defined for example 
in a C extension module.

When Python is running in a single thread, PyOS_InputHook is called ten times 
per second while Python is waiting for the user to type something. This is 
achieved by setting readline's rl_event_hook function to PyOS_InputHook.

When Python uses multiple threads, each thread has its own PyOS_InputHook (I am 
not sure if this was intended). However, with IDLE I noticed that the subprocess 
thread doesn't call its PyOS_InputHook. In IDLE (if I understand correctly how 
it works), one thread takes care of the GUI and the interaction with the user, 
while another thread executes the user's commands. If an extension module sets 
PyOS_InputHook, the PyOS_InputHook belonging to this second thread is set. 
However, this PyOS_InputHook does not get called. Is this simply an oversight? 
What would be a suitable place to add the call to PyOS_InputHook? In other 
words, where does the second thread go idle?

--Michiel.



> On Thu, Dec 09, 2004, Michiel Jan Laurens de Hoon wrote:
> 
>>>
>>> My suggestion is therefore to replace PyOS_InputHook by two functions
>>> PyOS_AddInputHook and PyOS_RemoveInputHook, and let Python keep track of
>>> which hooks are installed. This way, an extension module can add a hook
>>> function without having to worry about other extension modules trying
>>> to use the same hook.
>>> 
>>> Any comments? Would I need to submit a PEP for this proposal?
> 
> 
> Because this is only for the C API, your best bet is to write a patch
> and submit it to SF.  If people whine or it gets rejected, then write a
> PEP.


-- 
Michiel de Hoon, Assistant Professor
University of Tokyo, Institute of Medical Science
Human Genome Center
4-6-1 Shirokane-dai, Minato-ku
Tokyo 108-8639
Japan
http://bonsai.ims.u-tokyo.ac.jp/~mdehoon