Py004-01-13互斥锁

互斥锁

多线程下操作同一数据

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import time
from threading import Thread

n = 100

def task():
    global n
    temp = n
    time.sleep(0.1)
    n = temp-1

if __name__ == '__main__':
    arr = []
    for i in range(100):
        t = Thread(target=task)
        arr.append(t)
        t.start()

    # 保证所有线程都执行完毕
    for t in arr:
        t.join()

    print('主',n)

执行结果：
主 99

此时就不安全了，100个线程都操作了但是数据还是99

互斥锁的应用

牺牲效率来保证数据的安全——将并行变成串行

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import time
from threading import Thread,Lock

n = 100

def task(mutex):
    global n
    mutex.acquire()
    temp = n
    time.sleep(0.1)
    n = temp-1
    mutex.release()

if __name__ == '__main__':
    mutex=Lock()
    arr = []
    for i in range(100):
        t = Thread(target=task,args=(mutex,))
        arr.append(t)
        t.start()

    # 保证所有线程都执行完毕
    for t in arr:
        t.join()

    print('主',n)