Piet van Oostrum wrote:
grocery_stocker <cdal...@gmail.com> (gs) wrote:
gs> The following code gets data from 5 different websites at the "same
gs> time".
[snip]
gs> start = time.time()
gs> def main():
gs> for i in range(5):
gs> t = MyUrl(queue)
gs> t.setDaemon(True)
gs> t.start()
gs> for host in hosts:
gs> print "pushing", host
gs> queue.put(host)
gs> for i in range(5):
gs> queue.put(None)
gs> t.join()
gs> if __name__ == "__main__":
gs> main()
gs> print "Elapsed Time: %s" % (time.time() - start)
gs> How does the parallel download work if each thread has a lock? When
gs> the program opens www.yahoo.com, it places a lock on the thread,
gs> right? If so, then doesn't that mean the other 4 sites have to wait
gs> for the thread to release the lock?
No. Where does it set a lock? There is only a short lock period in the queue
when an item is put in the queue or got from the queue. And of course we
have the GIL, but this is released as soon as a long during operation is
started - in this case when the Internet communication is done.
Also, the code is creating 5 threads, but using join() on only the last
one.
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