how does a queue stop the thread?

[kaiix]

A simple thread pool example. My question is, since *MyThread.run*
will loop endless, how does the thread know the time to quit? how does
the *queue* notify the thread? is there any shared variables, like a
*lock*?

When I set daemon false, it stays in the loop, not quit any more.
what's the role does the daemon state plays?

code:
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import Queue
import threading

def do_some_thing(x):
    print int(x)

class MyThread(threading.Thread):
    def __init__(self, queue):
        threading.Thread.__init__(self)
        self.queue = queue

    def run(self):
        while True:
            params = self.queue.get()
            do_some_thing(params)
            self.queue.task_done()

q = Queue.Queue()

for i in range(1, 5):
    t = MyThread(q)
    t.setDaemon(True)
    t.start()

for x in range(10):
    q.put(x)

q.join()