python多线程同步机制Lock

#!/usr/bin/env python# -*- coding: utf-8 -*-

import threadingimport time

value = 0lock = threading.Lock()

def add():    global value    with lock:        new_value = value + 1        time.sleep(0.001)        value = new_value

if __name__ == ‘__main__‘:    threads = []    for i in range(100):        t = threading.Thread(target=add)        t.start()        threads.append(t)

    for t in threads:        t.join()

    print value    print ‘Main end‘

如果将with lock去掉，将得不到最终的值100.