I will note that the check-and-reinsert example given elsewhere in this thread contains a race condition in the multiple producer use case or in cases where a single producer may place additional items in the queue after the shutdown sentinel:
def _iterqueue(queue): while 1: item = queue.get() # Queue is not locked here, producers may insert more items # and other consumers may process items that were in the queue # after the sentinel if item is StopIteration: # We put StopIteration into the queue again, but it may not be # at the front if a producer inserted something after the original # insertion of the sentinel value queue.put(StopIteration) break else: yield item
You are quite right. The assumption is that the StopIteration singleton correctly marks the end of the queue however that is achieved (e.g. have the producer-spawning thread join() with all producers, then put StopIteration). Cheers, -- // aht http://blog.onideas.ws