[Tkinter-discuss] tkinter and multiprocessing

[Mark Summerfield]

Hi,

Silly me! I forgot to do the multiprocessing in a separate thread: now
it works:-)

On Wed, 29 Aug 2012 18:01:24 +0100
Mark Summerfield <list at qtrac.plus.com> wrote:
> Hi,
> 
> I'm trying to create a Tkinter application that uses multiprocessing in
> a separate module to do some work.
> 
> In the Tkinter part I have this method of my Window ttk.Frame subclass:
> 
>     def report(self, future):
>         with StatusLock: # Serialize calls to Window.report()
>             if future.exception() is None:
>                 result = future.result()
>                 print(result)
> # TODO why does this lock the application?
>                 self.statusText.set(result.name)
>                 self.master.update() # Make sure the GUI refreshes
> 
> StatusLock is a multiprocessing.Lock.
> self.statusText is a tk.StringVar.
> 
> This function is called by a multiprocessing Future:
> 
>     future = executor.submit(action, arg1, arg2)
>     future.add_done_callback(report)
> 
> When I run the program with the last two lines of report() commented out
> it correctly prints each result on the console. But with the last two
> lines uncommented it prints one result and then the whole application
> locks at the self.statusText.set() call.
> 
> According to the multiprocessing docs the callback is executed in the
> thread of the function it is passed -- so in this case in the GUI thread
> which is what is wanted.
> 
> Any suggestions/help welcome:-)
> 
> Thanks!

-- 
Mark Summerfield, Qtrac Ltd, www.qtrac.eu
    C++, Python, Qt, PyQt - training and consultancy
        "Programming in Go" - ISBN 0321774639
            http://www.qtrac.eu/gobook.html