python 线程信号量 -5

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from atexit import register from random import randrange from threading import BoundedSemaphore, Lock, Thread from time import sleep,ctime   lock = Lock() MAX = 5  # 最大线程数 candytray = BoundedSemaphore(MAX) def refill():     lock.acquire()     print('Refilling candy...')     try:         candytray.release()     except ValueError as e:         print('full, skipping', e)     else:         print('ok')     lock.release() def buy():     lock.acquire()     print('Buying candy...')     if candytray.acquire(False):         print('ok')     else:         print('empty, skipping')     lock.release()   def producer(loops):     for i in range(loops):         refill()  # 添加         sleep(randrange(3)) def consumer(loops):     for i in range(loops):         buy()  # 购买         sleep(randrange(3)) def _main():     print('starting at:', ctime())     nloops = randrange(2,6)     print(nloops)     print('THECHADY MACHINE (full with %d bars)!' % MAX)     Thread(target=consumer, args=(randrange(nloops,nloops+MAX+2),)).start() # buyer     Thread(target=producer, args=(nloops,)).start()   @register def _atexit():     print('all DONE at:', ctime())   if __name__ == '__main__':     _main()