线程锁模拟抢票系统

from multiprocessing import Process,Lock
import  json,random,time,os

def search():   #查票
    with open("db.txt",encoding='utf-8') as f:
        dic=json.load(f)
        print("%s 剩余票数 %s" %(os.getpid(),dic['count']))

def get():   #抢票
    with open("db.txt",encoding='utf-8') as read_f:
        dic = json.load(read_f)
        if dic['count'] > 0:
            dic['count'] -=1
            time.sleep(random.randint(1,3))   #模拟手速+网速
            with open("db.txt",'w', encoding='utf-8') as write_f:
                json.dump(dic,write_f)
                print("33[43;1m%s抢票成功33[0m "%os.getpid())

def task(lock):
    search()   #查找可能是并发执行，
    lock.acquire()   #抢票才要锁，这也是用join的另一个不同
    get()
    lock.release()
if __name__ == "__main__":
    lock = Lock()
    for i in range(20):
        p = Process(target=task,args=(lock,))
        p.start()

#锁和join都是把并发变为串行，但是锁比join灵活，lock能让局部串行，而lock只能让全局串行