"""
抢票!
多个用户在同时读写同一个数据
"""
from multiprocessing import Process,Lock
import json,time,random
# 查看余票
def show_ticket(name):
time.sleep(random.randint(1,3))
with open(r"ticket.json","rt",encoding="utf-8") as f:
dic = json.load(f)
print("%s查看 剩余票数:%s" % (name ,dic["count"]))
# 购买票
def buy_ticket(name):
# 购买前再次查询
with open(r"ticket.json", "rt", encoding="utf-8") as f:
# 修改数据
dic = json.load(f)
if dic["count"] > 0:
dic["count"] -= 1
# 模拟网络延迟
time.sleep(random.randint(1,3))
# 模拟服务器收到数据 写入文件
with open(r"ticket.json", "wt", encoding="utf-8") as f2:
json.dump(dic,f2)
print("%s 购票成功!" % name)
def task(lock,name):
# 查看余票可以并发执行 不需要锁住
show_ticket(name)
# 购票的操作需要锁 因为设涉及到同时修改数据
lock.acquire()
buy_ticket(name)
lock.release()
if __name__ == '__main__':
# 买个锁
mutex = Lock() # 所有子进程 必须是同一把锁，否则无法实现——锁定的状态
for i in range(11):
p = Process(target=task,args=(mutex,"客户%s" % i))
p.start()
# 查询票这个事情 可以多个进程同时执行
# 但是买票这个过程 不能同时进行 前一个没买完 后一个就不能买
