互斥锁

互斥锁：同一个资源不能由多个程序同时使用

由并发变成了串行

from multiprocessing import Process,Lock
import time
def task(name,mutex):
    mutex.acquire()
    print("%s 1" % name)
    time.sleep(1)
    print("%s 2" % name)
    time.sleep(1)
    print("%s 3" % name)
    time.sleep(1)
    mutex.release()
if __name__ == "__main__":
    mutex=Lock()#所有进程必须使用同一把锁
    for i in range(3):
        p=Process(target=task,args=("进程%s" % i,mutex))
        p.start()

练习题：

模拟抢票软件

from multiprocessing import Process,Lock
import json,time
def search(name):
    time.sleep(2)
    dict=json.load(open("db.txt","r",encoding="utf-8"))
    print("%s 查看到剩余票数[%s]" % (name,dict.get("count","")))
def get(name,mutex):
    mutex.acquire()
    time.sleep(2)
    dict = json.load(open("db.txt", "r", encoding="utf-8"))
    if dict.get("count",0) >0:
        dict["count"]-=1
        time.sleep(1)
        json.dump(dict,open("db.txt","w",encoding="utf-8"))
        print("%s 购票成功" % name)
    mutex.release()
def task(name,mutex):
    search(name)
    get(name,mutex)
if __name__=="__main__":
    mutex=Lock()
    for i in range(10):
        p=Process(target=task,args=(i,mutex))
        p.start()