优化抢票

优化抢票

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

def search():
    time.sleep(1) # 模拟网络io
    with open('db.txt',mode='rt',encoding='utf-8') as f:
        res = json.load(f)
        print(f'还剩{res["count"]}')

def get():
    with open('db.txt',mode='rt',encoding='utf-8') as f:
        res = json.load(f)
        # print(f'还剩{res["count"]}')
    time.sleep(1) # 模拟网络io
    if res['count'] > 0:
        res['count'] -= 1
        with open('db.txt',mode='wt',encoding='utf-8') as f:
            json.dump(res,f)
            print(f'进程{os.getpid()} 抢票成功')
        time.sleep(1.5) # 模拟网络io
    else:
        print('票已经售空啦!!!!!!!!!!!')

def task(lock):
    search()

    # 锁住
    lock.acquire()
    get()
    lock.release()
    # 释放锁头

if __name__ == '__main__':
    lock = Lock() # 写在主进程是为了让子进程拿到同一把锁.
    for i in range(15):
        p = Process(target=task,args=(lock,))
        p.start()
        # p.join()

    #  进程锁 是把锁住的代码变成了串行
    #  join 是把所有的子进程变成了串行


# 为了保证数据的安全,串行牺牲掉效率.


db.txt写入{"count": 3}