Newbie having issues with threads

[Raja Baz]

On Thu, 31 Jul 2008 14:09:12 -0700, James Calivar wrote:

> I'm a newbie trying to write a script that uses threads.  I'm right now
> a little bit stuck in understanding why the code snippet I wrote doesn't
> seem to be entering the function defined in the start_new_thread() call.
> 
> If I run it as is (the threaded version), the output is:
> 
> UA_1 configuring...
> UA_1 halting..
> 
> But if I comment out the line w/ the thread and just call the function
> directly, everything seems to work OK:
> 
> UA_1 configuring...
> UA_1 executing...
> UA_1 halting...
> 
> Can anyone tell me why the thread doesn't seem to invoke the function
> "execute()"?  I'm running Python 2.4.3.
> 
> Here is my code:
> 
> ===========
> import thread
> 
> class Test(object):
>     def __init__(self, instanceID):
>         self.instanceID = instanceID
>     def configure(self):
>         print self.instanceID + " configuring..."
>     def execute(self):
>         print self.instanceID + " executing..."
>     def halt(self):
>         print self.instanceID + " halting..."
> 
> if __name__ == "__main__":
>     """usage: sipp_auto [options]"""
> 
>     ua1 = Test("UA_1")
> 
>     ua1.configure()
> 
>     #ua1.execute()
>     thread.start_new_thread(ua1.execute, ())
> 
>     ua1.halt()
> 
> ===========
> Thanks, James

I've run into this problem before. The main problem is that the thread 
started via start_new_thread exits when the program does(instead of 
finishing its work first). So what happens here is that sometimes it may 
have the time to execute, and sometimes it won't

changing:
thread.start_new_thread(ua1.execute, ())

ua1.halt()

to:
thread.start_new_thread(ua1.execute, ())
from time import sleep
sleep(0.01) # this is barely even noticeable

ua1.halt()

fixes the problem in this case and the output is correct.

However, you seem to have taken up using the threading module which is 
probably better anyway, just wanted to explain why this was happening.