[Tutor] [tutor] Question on multithreading

[bob gailer]

Varsha Purohit wrote:
> Hello friends,
>         I hve a GUI where i have start button and stop button. When i 
> press start button one thread is created and it is executing some 
> background task and when i press stop button that thread is 
> stopped/killed. These two things are working properly. But i have to 
> implement pause button in my GUI. When i press pause the thread 
> execution should come to a halt and after that it should be resumed 
> when i press pause again or may be i can implement some other button.
>
> Does anybody have an example where they have implemented this kind of 
> threading concept ??
Take a look at the threading module. The thread should acquire() a 
condition then wait(). The following is quickly thrown together and not 
tested.

main program:
import threading
cond = threading.Condition() # create a condition variable with a new RLock

thread:
while True: # I assume the thread runs in some kind of loop
  if pause: # pressing Pause should set this variable True
    cond .acquire()
    cond .wait() # pauses until notified
    cond .release()
    # rest of thread - assumes loop repeats fast enough to give the 
desired response time

code behind the pause/resume button:
pause = not pause # toggle
if not pause:
  cond.notify()

-- 
Bob Gailer
919-636-4239 Chapel Hill, NC