如何在 Python 中锁定部分方法

Question

我想锁定部分方法（"Waiting to acquire lock" 之后的部分应该只在第一个线程释放锁后运行）。发生的情况是两个线程运行独立地与 lock.acquire() 无关。

我不明白为什么这不起作用。 Whosebug 中的示例与此类似但不完全相同。只是一瞥为什么我需要这个：我没有明确的共享资源，我只是想防止 2 python 线程从运行ning 相同的代码，因为在我工作的系统中上，他们可能会使系统处于不稳定状态。

import threading, time

def test(name):
    lock = threading.Lock()

    print(name + " - Starting thread")
    print(name + " - Waiting to acquire lock")
    lock.acquire(True)
    try:
        print(name + " - Lock acquired!")
        for i in range(10):

            print(name + " - " + str(i))
            print("")
            time.sleep(1)
    finally:
        lock.release()
        print(name + " - Lock released")

def main():

    t1 = threading.Thread(target=test, args=["#1_Thread"])
    t2 = threading.Thread(target=test, args=["#2_Thread"])

    t1.start()
    time.sleep(3)
    t2.start()

main()

Answer 1

您创建的锁定对象是您的函数的本地对象，因此不共享：

lock = threading.Lock()

将您的锁定义为全局锁，它将被共享

import threading, time
lock = threading.Lock()

def test(name):
    global lock

    print(name + " - Starting thread")
    print(name + " - Waiting to acquire lock")
    lock.acquire(True)
    try:
        print(name + " - Lock acquired!")
        for i in range(10):

            print(name + " - " + str(i))
            print("")
            time.sleep(1)
    finally:
        lock.release()
        print(name + " - Lock released")

def main():

    t1 = threading.Thread(target=test, args=["#1_Thread"])
    t2 = threading.Thread(target=test, args=["#2_Thread"])

    t1.start()
    time.sleep(3)
    t2.start()

main()

Answer 2

您的线程各自创建并锁定自己的独立锁：

def test(name):
    lock = threading.Lock()
    ...

那不会提供互斥。两个线程可以同时加不同的锁，不会冲突；只有当两个线程试图锁定 相同的 锁时，锁才会做任何事情。

创建一个锁并将其提供给两个线程。当您使用它时，with 语句通常是一种比 finally 块更干净的方式来确保清理。 That'll lock the lock when execution enters the with and unlock it when execution leaves:

import threading, time

def test(name, lock):
    print(name + " - Starting thread")
    print(name + " - Waiting to acquire lock")
    with lock:
        print(name + " - Lock acquired!")
        for i in range(10):

            print(name + " - " + str(i))
            print("")
            time.sleep(1)
    print(name + " - Lock released")

def main():
    lock = threading.Lock()

    t1 = threading.Thread(target=test, args=["#1_Thread", lock])
    t2 = threading.Thread(target=test, args=["#2_Thread", lock])

    t1.start()
    time.sleep(3)
    t2.start()

main()

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