[Tkinter-discuss] Tkinter and threading

[Russell E. Owen]

In article <ifz1al.3ldie0 at www.pandorasdream.com>,
 Vania Smrkovski <vania at pandorasdream.com> wrote:

> Hello,
>   New to this group, and I have not found much in the way of documentation 
>   for advanced uses of Tkinter, yet.  So far, Tk3k is the most advanced 
>   resource I have found yet.
>   I am trying to implement threading in my Tkinter app.  I have managed to 
>   get a button to fire an FTP download into one of my text areas, but to get 
>   rid of the delay on the GUI while the FTP process was being handled, I 
>   created a thread in the button\'s command handler....

You cannot safely make Tkinter from any thread other than the one that 
started the tkinter mainloop (i.e. your main thread unless you are doing 
something really weird).

As far as network communication goes, you have several options...
- Use the free "twisted framework". It integrates with Tkinter and other 
GUI toolkits, handles most of the standard protocols and is reported to 
be very good.

- For ftp, do the transfer in the background and poll the state. This is 
especially appropriate if you have multiple transfers since one polling 
loop can poll all of them. For an example see RO.Comm.FTPGet and the 
associated widget RO.Wdg.FTPLogWdg in the RO package 
<http://www.astro.washington.edu/rowen/ROPython.html>.

- For TCP/IP use a tcl socket and use file events to handle incoming 
data and errors. This has the advantage of being asynchronous (and is 
completely cross platform unlike the a similar technique at the Tkinter 
level). For an example see RO.Comm.TCPConnection and the underlying 
RO.Comm.TkSocket.

-- Russell

P.S. there were rumors a few years ago that you could safely generate 
Tkinter events from a background thread and have the main thread handle 
them. However, I am pretty sure (based on my own tests) that it's not 
actually safe to do that. My suggestion is to NEVER deal with Tkinter or 
Tk from a background thread.