Python 多线程 互斥锁

'''
1. threading 模块中定义 Lock() 锁
2. acquire 加锁 release 释放锁
3. 如果在调用acquire方法时，其他线程已经使用六这个互斥锁，那么此时acquire方法会堵塞，知道这个互斥锁释放后才能再次上锁
4. Lock有 acquire() 和 release()。成对出现， 先释放锁后才能加锁 否则会造成死锁

'''
from threading import Thread,Lock

a = 0
b = 1000000

#创建全局互斥锁
lock = Lock()

def sum1():
    for i in range(b):
        global a
        a += 1
    print("第1次:",a)

def sum2():
    for i in range(b):
        global a
        a += 1
    print("第2次:",a)

def sum3():
    lock.acquire()
    for i in range(b):
        global a
        a += 1
    print("第1次:",a)
    lock.release()

def sum4():
    lock.acquire()
    for i in range(b):
        global a
        a += 1
    print("第2次:",a)
    lock.release()


if __name__ == '__main__':

    # 没有加互斥锁
    # t1 = Thread(target=sum1)
    # t2 = Thread(target=sum2)
    '''
    第1次: 1348006
    第2次: 1522249
    '''

    # 加 互斥锁
    t1 = Thread(target=sum3)
    t2 = Thread(target=sum4)
    '''
    第1次: 1000000
    第2次: 2000000
    '''

    t1.start()
    t2.start()

{/tabs-pane}
{tabs-pane label="阻塞主线程，实现同步"}

from threading import Thread

a = 0
b = 1000000

def sum1():
    for i in range(b):
        global a
        a += 1
    print("第1次:",a)

def sum2():
    for i in range(b):
        global a
        a += 1
    print("第2次:",a)



if __name__ == '__main__':

    # 没有加互斥锁
    t1 = Thread(target=sum1)
    t2 = Thread(target=sum2)


    t1.start()
    t1.join() # 阻塞主线程，等待子线程执行完
    t2.start()

    '''
    第1次: 1000000
    第2次: 2000000
    '''

{/tabs-pane}