进程锁的示意图：

　　锁.py:

1 #锁 2 #火车票 3 import json 4 import time 5  6 from multiprocessing import Process 7 from multiprocessing import Lock 8  9 def show(i):10     with open('ticket') as f:11         dic = json.load(f)12     print('余票：%s'%dic['ticket'])13 14 def buy_ticket(i,lock):15     lock.acquire()  #拿钥匙进门16     with open('ticket') as f:17         dic = json.load(f)18         time.sleep(0.1)19     if dic['ticket'] > 0:20         dic['ticket'] -= 121         print('\033[32m%s买到票了\033[0m'%i)22     else:23         print('\033[31m%s没买到票\033[0m'%i)24     time.sleep(0.1)25     with open('ticket','w') as f:26         json.dump(dic,f)27     lock.release()  #还钥匙28 29 if __name__ == '__main__':30     for i in range(10):31         p = Process(target=show, args=(i,))32         p.start()33     lock = Lock()34     for i in range(10):35         p = Process(target=buy_ticket, args=(i,lock))36         p.start()

运行结果：