python进程锁

# 进程锁的代价是，失去异步效果
# db.txt文件内容：{"count": 1}

from multiprocessing import Process
from multiprocessing import Lock
import time
import json

def search():
        time.sleep(1)
        f = open('json.txt','r',encoding='utf-8')
        ticket =json.load(f)
        print(f"剩余票数：{ticket['count']}")
        f.close()
        return ticket
def buy():
      ticket = search()
      if ticket['count'] > 0:
              ticket['count'] -=1
              print('购买完成')
              f = open('json.txt', 'w')
              f.write(json.dumps(ticket))


def task(lock):
        lock.acquire() # 上锁
        buy()
        lock.release() #解锁

if __name__ == '__main__':
    lock = Lock()
    for i in range(3):
            p = Process(target=task,args=(lock,)) # 创建三个进程，每个进程都加锁，表示该进程完成后才能执行下个进程
            p.start()


返回结果：
剩余票数：1
购买完成
剩余票数：0
剩余票数：0