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tkinter test field, scrolling, threads

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?

Bob


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Jul 18 '05 #1
3 2199
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:

--text+threads.py------------------
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
--
- Eric Brunel <eric dot brunel at pragmadev dot com> -
PragmaDev : Real Time Software Development Tools - http://www.pragmadev.com

Jul 18 '05 #2
Eric Brunel <er*********@N0SP4M.com> wrote in message news:<c1**********@news-reader2.wanadoo.fr>...
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:

--text+threads.py------------------
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.

Thanks!
Jul 18 '05 #3
Bob Greschke wrote:
[snip]
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.


Did you try to run your script outside of IDLE, i.e. just by opening a DOS
console and type "python myScript.py"? Since IDLE is itself written with
Tkinter, there may a few problems between your script and IDLE itself.

HTH
--
- Eric Brunel <eric (underscore) brunel (at) despammed (dot) com> -
PragmaDev : Real Time Software Development Tools - http://www.pragmadev.com

Jul 18 '05 #4

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