tkinter test field, scrolling, threads

Bob Greschke bob at
Thu Mar 11 00:09:16 CET 2004

Eric Brunel <eric.brunel at> wrote in message news:<c1uubt$vlh$1 at>...
> Bob Greschke wrote:
> > I have a program where the user pushes a button, a "starting" message is
> > .inserted to a text field with an associated scroll bar, a thread is started
> > that inserts a "working..." message on to the end of the text field until
> > stopped, or until the loop finishes.  The loop sleeps for about 3 seconds
> > every time through (I'm just prototyping at this point).  The mainloop just
> > waits for the user to hit the same button again which will set a flag and
> > cause the thread to terminate early, otherwise it doesn't have anything to
> > do.  update()'s and update_idle_tasks() get called anytime anything is
> > written to the text field.  Everything works fine until the text field fills
> > up then the program just freezes with no errors on the console window.  If I
> > change the starting of a thread to a regular function call then everything
> > works fine.
> > 
> > What is going wrong?
> If you do not post any code, it will be difficult for anyone to help you. 
> Knowing your Python and tcl/tk versions and your platform will help too.
> I know that there are some issues regarding Tkinter and threads, but the 
> following code works:
> from Tkinter import *
> import time, threading
> root = Tk()
> t = Text(root, width=8, height=4)
> t.pack(side=LEFT, fill=BOTH)
> vs = Scrollbar(root, orient=VERTICAL, command=t.yview)
> vs.pack(side=RIGHT, fill=Y)
> t.configure(yscrollcommand=vs.set)
> root.update()
> def thLoop():
>    i = 0
>    while 1:
>      t.insert(END, 'spam %s\n' % i)
>      i += 1
>      time.sleep(1)
> th = threading.Thread(target=thLoop)
> th.setDaemon(1)
> th.start()
> root.mainloop()
> -----------------------------------
> Tested with Python 2.1.1, tcl/tk 8.3.2 on Linux Mandrake 8.0

Sorry...this is WinXP, Python 2.3.3

I'm still messing with this.  Your program seems to work fine.  No
matter how I mess with it I can't get it to fail, but even if I strip
a lot out of mine it keeps behaving badly.  But it is even wierder. 
If I "print" any ol' thing to the IDLE console window from a thread,
and keep doing it until the console window fills up to the point where
it should start to scroll, everything IDLE crashes and freezes.  The
exact same code works fine on RH9 Python 2.2.2, and Solaris 8 Python
2.1.1.  For now I've just turned off the scroll bars when in Windows. 
I'd post code, but the program is now pretty big and I'm not sure what
to keep or throw out.


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