【Python】互斥锁与 抢票程序

# 互斥锁   把多个并发处理资源的进程变成串行
# 互斥锁与join 的区别:
#   join 把代码整体变成串行

# from multiprocessing import Process, Lock
# # import time
# #
# #
# # def task(name, mutex):
# #     mutex.acquire()  # 拿锁
# #     print('%s 1' % name)
# #     time.sleep(1)
# #     print('%s 2' % name)
# #     time.sleep(1)
# #     print('%s 3' % name)
# #     time.sleep(1)
# #     mutex.release()  # 解锁
# #
# #
# # if __name__ == '__main__':
# #     mutex = Lock()
# #     for i in range(3):
# #         p = Process(target=task, kwargs={'name': '进程%s' % i, 'mutex': mutex})
# #         p.start()

# 抢票系统
import time, json
from multiprocessing import Process, Lock

# data = {'count':3}
# json.dump(data, open('db.txt', 'w', encoding='utf-8'))

def search(name, mutex):
    time.sleep(1)
    dic = json.load(open('db.txt', 'r', encoding='utf-8'))
    print('<%s> 查看剩余票数 [%s]' % (name, dic['count']))
    get(name, mutex)


def get(name, mutex):
    mutex.acquire()
    time.sleep(1)
    dic = json.load(open('db.txt', 'r', encoding='utf-8'))
    if dic['count'] > 0:
        dic['count'] -= 1
        time.sleep(3)
        json.dump(dic, open('db.txt', 'w', encoding='utf-8'))
        print('%s 购票成功' % name)
    mutex.release()


def task(name):
    search(name)
    get(name)


if __name__ == '__main__':
    mutex = Lock()
    for i in range(10):
        p = Process(target=search, kwargs={'name': '路人%s' % i, 'mutex': mutex})
        p.start()