Python（线程锁）

1. 为什么要设置线程锁

1.1 多个线程对同一个数据进行修改时，可能会出现不可预料的情况.

2. 如何实现线程锁

2.1 实例化对象方式实现线程锁：

import threading


#  银行存钱和取钱
def add(lock):
    global money  # 声明money为全局变量
    for i in range(1000000):
        # 2. 操作变量之前进行加锁
        lock.acquire()
        money += 1  # money;  money+1; money=money+1;
        # 3. 操作变量之后进行解锁
        lock.release()


def reduce(lock):
    global money
    for i in range(1000000):
        # 2. 操作变量之前进行加锁
        lock.acquire()
        money -= 1
        # 3. 操作变量之后进行解锁
        lock.release()


if __name__ == '__main__':
    money = 0
    # 1. 实例化一个锁对象;
    lock = threading.Lock()

    t1 = threading.Thread(target=add, args=(lock,))
    t2 = threading.Thread(target=reduce, args=(lock,))
    t1.start()
    t2.start()
    t1.join()
    t2.join()

    print("当前金额:", money)

2.2 继承方式实现线程锁：

import threading
class AddThread(threading.Thread):
    def __init__(self, lock):
        super(AddThread, self).__init__()
        self.lock = lock
    def run(self):
        for i in range(1000000):
            # 2. 操作变量之前进行加锁
            self.lock.acquire()
            global  money
            money += 1  # money;  money+1; money=money+1;
            # 3. 操作变量之后进行解锁
            self.lock.release()

class ReduceThread(threading.Thread):
    def __init__(self, lock):
        super(ReduceThread, self).__init__()
        self.lock = lock
    def run(self):
        global money
        for i in range(1000000):
            # 2. 操作变量之前进行加锁
            lock.acquire()
            money -= 1
            # 3. 操作变量之后进行解锁
            lock.release()
if __name__ == '__main__':
    money = 0
    # 1. 实例化一个锁对象;
    lock = threading.Lock()
    t1 = AddThread(lock)
    t2 = ReduceThread(lock)
    t1.start()
    t2.start()
    t1.join()
    t2.join()
    print("当前金额:", money)