Stop a thread on deletion

[Sjoerd Op 't Land]

Hello all,

I'm using threading for generating video content. The trouble is how to 
kill the thread, because there are multiple (simultaneous) owners of a 
thread. Ideally, a flag would be set when the reference count of the 
thread becomes zero, causing the run() loop to quit. Example:

import threading
import time
import gc

class myThread(threading.Thread):
   def __init__(self):
     self.passedOut = threading.Event()
     threading.Thread.__init__(self)
   def __del__(self):
     self.passedOut.set()
   def run(self):
     i = 0
     while not self.passedOut.isSet():
       i += 1
       print "Hi %d" % i
       time.sleep(0.25)


a = myThread()
a.start()
time.sleep(2.5)
a = None
time.sleep(2.5)

Unfortunately, this doesn't work. When I remove the while-loop, __del__ 
is called, actually. Appearantly there is still some reference to the 
thread while it is running.

I tried gc.get_referrers(self), but it seems to need some parsing. I'm 
not sure how to implement that and I'm not sure whether it will work 
always or not.

Thanks in advance for any suggestion,
Sjoerd Op 't Land