Use threads or Tkinter event loop?

[kyosohma at gmail.com]

On Mar 27, 9:07 am, Kevin Walzer <k... at codebykevin.com> wrote:
> Kevin Walzer wrote:
> > I'm trying to decide whether I need threads in my Tkinter application or
> > not. My app is a front end to a command-line tool; it feeds commands to
> > the command-line program, then reads its output and displays it in a
> > Tkinter text widget. Some of the commands are long-running and/or return
> > thousands of lines of output.
>
> > I initially thought I needed to use threading, because the GUI would
> > block when reading the output, even when I configured the blocking to be
> > non-blocking. I got threading to work, but it seemed a bit complicated.
> > So, I decided to try something simpler, by using the Tkinter event loop
> > to force the output to update/display.
>
> > it seems to work well enough. Here is my threaded code:
>
> > non-threaded:
>
> > def insertDump(self):
> >  self.finkinstalled = os.popen('/sw/bin/fink list', 'r', os.O_NONBLOCK)
> >         for line in self.finkinstalled:
> >             self.t.insert(END, line)
> >             self.update()
> >             self.t.see(END)
>
> > And here is my non-threaded code (needs two functions to work)
>
> >  def insertDump(self):
> >         try:
> >             data = self.dataQueue.get(block=False)
> >             for line in data:
> >                 self.t.insert(END, line)
> >                 self.t.see(END)
> >                 self.update()
>
> >         except:
> >             print "error"
> >             raise
>
> >     def getDump(self):
>
> >         self.file = os.popen('/sw/bin/fink list', 'r', os.O_NONBLOCK)
> >         self.dataQueue.put(self.file)
>
> > This brings me to a design, as opposed to coding, question. The
> > non-threaded version seems to work just as well as the threaded one, in
> > terms of speed. Moreover, it is simpler to code and debug, because I
> > don't have to check to make sure the thread queue has data (I sometimes
> > get an 'Empty' error message when I first start the thread).  Simply
> > using the Tk event loop (self.update) is also how I would have coded
> > this in Tcl.
>
> > So my question is this: under what circumstances in Python are threads
> > considered "best practice"? Am I wrong to use the Tk event loop instead
> > of threads?
>
> D'oh, I got the code snippets mixed up:
>
> non-threaded:
>
> def insertDump(self):
>   self.finkinstalled = os.popen('/sw/bin/fink list', 'r', os.O_NONBLOCK)
>          for line in self.finkinstalled:
>              self.t.insert(END, line)
>              self.update()
>              self.t.see(END)
>
> threaded:
>
>   def insertDump(self):
>          try:
>              data = self.dataQueue.get(block=False)
>              for line in data:
>                  self.t.insert(END, line)
>                  self.t.see(END)
>                  self.update()
>
>          except:
>              print "error"
>              raise
>
>      def getDump(self):
>
>          self.file = os.popen('/sw/bin/fink list', 'r', os.O_NONBLOCK)
>          self.dataQueue.put(self.file)
>
> Sorry!
> --
> Kevin Walzer
> Code by Kevinhttp://www.codebykevin.com

It looks like Tkinter is similar to wxPython in that you're not
supposed to use the mainloop for anything except the GUI and GUI
commands. The following websites have more info on Tkinter and
threads:

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/82965
http://www.thescripts.com/forum/thread22536.html
http://forums.devshed.com/python-programming-11/tkinter-threads-123001.html

I use the Threading module for threading in wxPython. I think that
would probably serve you well with Tkinter as well. You can use the
join() method to wait for all the threads to exit.

Mike