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标题: 详解 5 种 Python 线程锁（二） [打印本页]

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作者: 气泡水    时间: 2021-11-22 14:49
标题: 详解 5 种 Python 线程锁（二）
　　3、Condition() 条件锁

　　基本介绍

　　条件锁是在递归锁的基础上增加了能够暂停线程运行的功能。并且我们可以使用wait()与notify()来控制线程执行的个数。

　　注意：条件锁可以自由设定一次放行几个线程。

　　使用方式

　　下面这个案例会启动10个子线程，并且会立即将10个子线程设置为等待状态。

　　然后我们可以发送一个或者多个通知，来恢复被等待的子线程继续运行：

[Python] 纯文本查看 复制代码

import threading



currentRunThreadNumber = 0

maxSubThreadNumber = 10





def task():

    global currentRunThreadNumber

    thName = threading.currentThread().name



    condLock.acquire()  # 上锁

    print("start and wait run thread : %s" % thName)



    condLock.wait()  # 暂停线程运行、等待唤醒

    currentRunThreadNumber += 1

    print("carry on run thread : %s" % thName)



    condLock.release()  # 解锁





if __name__ == "__main__":

    condLock = threading.Condition()



    for i in range(maxSubThreadNumber):

        subThreadIns = threading.Thread(target=task)

        subThreadIns.start()



    while currentRunThreadNumber < maxSubThreadNumber:

        notifyNumber = int(

            input("Please enter the number of threads that need to be notified to run："))



        condLock.acquire()

        condLock.notify(notifyNumber)  # 放行

        condLock.release()



    print("main thread run end")

    

# 先启动10个子线程，然后这些子线程会全部变为等待状态

# start and wait run thread : Thread-1

# start and wait run thread : Thread-2

# start and wait run thread : Thread-3

# start and wait run thread : Thread-4

# start and wait run thread : Thread-5

# start and wait run thread : Thread-6

# start and wait run thread : Thread-7

# start and wait run thread : Thread-8

# start and wait run thread : Thread-9

# start and wait run thread : Thread-10



# 批量发送通知，放行特定数量的子线程继续运行

# Please enter the number of threads that need to be notified to run：5  # 放行5个

# carry on run thread : Thread-4

# carry on run thread : Thread-3

# carry on run thread : Thread-1

# carry on run thread : Thread-2

# carry on run thread : Thread-5



# Please enter the number of threads that need to be notified to run：5  # 放行5个

# carry on run thread : Thread-8

# carry on run thread : Thread-10

# carry on run thread : Thread-6

# carry on run thread : Thread-9

# carry on run thread : Thread-7



# Please enter the number of threads that need to be notified to run：1

# main thread run end

　　with语句

　　由于threading.Condition()对象中实现了__enter__()与__exit__()方法，故我们可以使用with语句进行上下文管理形式的加锁解锁操作：

[Python] 纯文本查看 复制代码

import threading



currentRunThreadNumber = 0

maxSubThreadNumber = 10





def task():

    global currentRunThreadNumber

    thName = threading.currentThread().name



    with condLock:

        print("start and wait run thread : %s" % thName)

        condLock.wait()  # 暂停线程运行、等待唤醒

        currentRunThreadNumber += 1

        print("carry on run thread : %s" % thName)





if __name__ == "__main__":

    condLock = threading.Condition()



    for i in range(maxSubThreadNumber):

        subThreadIns = threading.Thread(target=task)

        subThreadIns.start()



    while currentRunThreadNumber < maxSubThreadNumber:

        notifyNumber = int(

            input("Please enter the number of threads that need to be notified to run："))



        with condLock:

            condLock.notify(notifyNumber)  # 放行



    print("main thread run end")

　　4、Event() 事件锁

　　基本介绍

　　事件锁是基于条件锁来做的，它与条件锁的区别在于一次只能放行全部，不能放行任意个数量的子线程继续运行。

　　我们可以将事件锁看为红绿灯，当红灯时所有子线程都暂停运行，并进入“等待”状态，当绿灯时所有子线程都恢复“运行”。

　　使用方式

　　事件锁不能利用with语句来进行使用，只能按照常规方式。

　　如下所示，我们来模拟线程和红绿灯的操作，红灯停，绿灯行：

[Python] 纯文本查看 复制代码

import threading



maxSubThreadNumber = 3





def task():

    thName = threading.currentThread().name

    print("start and wait run thread : %s" % thName)

    eventLock.wait()  # 暂停运行，等待绿灯

    print("green light, %s carry on run" % thName)

    print("red light, %s stop run" % thName)

    eventLock.wait()  # 暂停运行，等待绿灯

    print("green light, %s carry on run" % thName)

    print("sub thread %s run end" % thName)





if __name__ == "__main__":



    eventLock = threading.Event()



    for i in range(maxSubThreadNumber):

        subThreadIns = threading.Thread(target=task)

        subThreadIns.start()



    eventLock.set()  # 设置为绿灯

    eventLock.clear()  # 设置为红灯

    eventLock.set()  # 设置为绿灯



# start and wait run thread : Thread-1

# start and wait run thread : Thread-2

# start and wait run thread : Thread-3



# green light, Thread-1 carry on run

# red light, Thread-1 stop run

# green light, Thread-1 carry on run

# sub thread Thread-1 run end



# green light, Thread-3 carry on run

# red light, Thread-3 stop run

# green light, Thread-3 carry on run

# sub thread Thread-3 run end



# green light, Thread-2 carry on run

# red light, Thread-2 stop run

# green light, Thread-2 carry on run

# sub thread Thread-2 run end

　　5、Semaphore() 信号量锁

　　基本介绍

　　信号量锁也是根据条件锁来做的，它与条件锁和事件锁的区别如下：

　　条件锁：一次可以放行任意个处于“等待”状态的线程

　　事件锁：一次可以放行全部的处于“等待”状态的线程

　　信号量锁：通过规定，成批的放行特定个处于“上锁”状态的线程

　　使用方式

　　以下是使用示例，你可以将它当做一段限宽的路段，每次只能放行相同数量的线程：

[Python] 纯文本查看 复制代码

import threading

import time



maxSubThreadNumber = 6





def task():

    thName = threading.currentThread().name

    semaLock.acquire()

    print("run sub thread %s" % thName)

    time.sleep(3)

    semaLock.release()





if __name__ == "__main__":

    # 每次只能放行2个

    semaLock = threading.Semaphore(2)



    for i in range(maxSubThreadNumber):

        subThreadIns = threading.Thread(target=task)

        subThreadIns.start()





# run sub thread Thread-1

# run sub thread Thread-2



# run sub thread Thread-3

# run sub thread Thread-4



# run sub thread Thread-6

# run sub thread Thread-5

　　with语句

　　由于threading.Semaphore()对象中实现了__enter__()与__exit__()方法，故我们可以使用with语句进行上下文管理形式的加锁解锁操作：

[Python] 纯文本查看 复制代码

import threading

import time



maxSubThreadNumber = 6





def task():

    thName = threading.currentThread().name

    with semaLock:

        print("run sub thread %s" % thName)

        time.sleep(3)





if __name__ == "__main__":



    semaLock = threading.Semaphore(2)



    for i in range(maxSubThreadNumber):

        subThreadIns = threading.Thread(target=task)

        subThreadIns.start()

　　

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