python 锁，,作用：异步修改数据时

python 锁，,作用：异步修改数据时

作用：异步修改数据时，会造成数据安全问题，子进程分别进入文件/数据库，修改数据

"""过程：1.导入Lock模块2.创建Lock对象3.Lock对象做为要锁的进程的参数4.lock.acquire()5.lock.release()"""from multiprocessing import Processfrom multiprocessing import Lockdef for_fun(lock):    lock.acquire()    pass    lock.release()if __name__ == ‘__main__‘:    lock = Lock()    p = Process(target=for_fun(), args=(lock, ))

# 查看、购买电影票# 购买要设置锁，涉及到数据的修改import timeimport jsonfrom multiprocessing import Processfrom multiprocessing import Lockdef read(name):    with open(file=‘ticket‘, mode=‘r‘, encoding=‘utf-8‘) as f:        ret = json.load(f)[‘ticket‘]        print(‘%s查询，还剩%s张票‘ % (name, ret))def buy(name, lock):    lock.acquire()      # 拿钥匙    with open(file=‘ticket‘, mode=‘r‘, encoding=‘utf-8‘) as f:        ret = json.load(f)        time.sleep(0.1)    if ret[‘ticket‘] > 0:        ret[‘ticket‘] -= 1        print(‘%s购买成功‘ % name)    else:        print(‘%s购买失败‘ % name)    time.sleep(0.1)    with open(file=‘ticket‘, mode=‘w‘, encoding=‘utf-8‘) as f:        json.dump(ret, f)        time.sleep(0.1)    lock.release()      # 还钥匙if __name__ == ‘__main__‘:    lock = Lock()    lock.acquire    for i in range(1, 3):        p = Process(target=read, args=(‘tom%s‘ % i, ))        p.start()        p = Process(target=buy, args=(‘tom%s‘ % i, lock))        p.start()"""结果：tom1查询，还剩1张票tom2查询，还剩1张票tom2购买成功tom1购买失败"""

python 锁