沒有加鎖的代碼如下

from atexit import register from random import randrange from threading import Thread, currentThread from time import sleep, ctimeclass CleanOutputSet(set):def __str__(self):return ', '.join(x for x in self)loops = (randrange(2, 5) for x in xrange(randrange(3, 7))) remaining = CleanOutputSet()def loop(nsec):myname = currentThread().nameremaining.add(myname)print '[%s] Start %s' % (ctime(), myname)sleep(nsec)remaining.remove(myname)print '[%s] Completed %s (%d sec)' % (ctime(), myname, nsec)print ' remaining: %s' % (remaining or 'NONE')def main():for pause in loops:Thread(target=loop, args=(pause,)).start()@register def _atexit():print 'End'if __name__ == '__main__':main()

沒有加鎖的情況下輸出（中間或者后面的那些空行也是輸出的部分）

[Fri Mar 09 21:17:53 2018] Start Thread-1 [Fri Mar 09 21:17:53 2018] Start Thread-2 [Fri Mar 09 21:17:53 2018] Start Thread-3 [Fri Mar 09 21:17:53 2018] Start Thread-4 [Fri Mar 09 21:17:53 2018] Start Thread-5 [Fri Mar 09 21:17:55 2018] Completed Thread-4 (2 sec)remaining: Thread-5, Thread-3, Thread-2, Thread-1 [Fri Mar 09 21:17:55 2018] Completed Thread-5 (2 sec)remaining: Thread-3, Thread-2, Thread-1 [Fri Mar 09 21:17:57 2018] Completed Thread-3 (4 sec)[Fri Mar 09 21:17:57 2018] Completed Thread-1 (4 sec)[Fri Mar 09 21:17:57 2018] Completed Thread-2 (4 sec)remaining: NONE remaining: NONE remaining: NONE

由于沒有加鎖導致在輸出的過程中，會使得整個IO變的很亂，還有，處理在全局變量中的remaining 那個set繼承下來的東西時，會變的很麻煩。

總之，我們需要學習加鎖的機制，只有這樣才能更好地使用并發的機制。

加鎖的代碼

關鍵代碼：

from threading import Thread, currentThread, Lock lock = Lock() # 放到全局變量當中

修改一下對應的loop部分，其他地方不變

def loop(nsec):myname = currentThread().namelock.acquire()remaining.add(myname)print '[%s] Start %s' % (ctime(), myname)lock.release()sleep(nsec)lock.acquire()remaining.remove(myname)print '[%s] Completed %s (%d sec)' % (ctime(), myname, nsec)print ' remaining: %s' % (remaining or 'NONE')lock.release()

或者是改成這樣也是可以的

def loop(nsec):myname = currentThread().namewith lock:remaining.add(myname)print '[%s] Start %s' % (ctime(), myname)sleep(nsec)with lock:remaining.remove(myname)print '[%s] Completed %s (%d sec)' % (ctime(), myname, nsec)print ' remaining: %s' % (remaining or 'NONE')

總結

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