how does a queue stop the thread?

[kaiix]

@kushal, thanks for your replies.

before i wrote the email, i've already read the python docs carefully.
i need the proof from code, i mean python source code. i tried to
prove some of my assumptions that lead the loop quit, and i traced
back to Queue.py, threading.py, dummy_thread.py, now i need some hints
to help me understanding the sample from python source code.