Python上的信号量

问题描述

几周前，我开始使用Python进行编程，并试图使用Semaphores来同步两个简单线程，以达到学习目的.这是我所拥有的:

I've started programming in Python a few weeks ago and was trying to use Semaphores to synchronize two simple threads, for learning purposes. Here is what I've got:

import threading
sem = threading.Semaphore()

def fun1():
    while True:
        sem.acquire()
        print(1)
        sem.release()

def fun2():
    while True:
        sem.acquire()
        print(2)
        sem.release()

t = threading.Thread(target = fun1)
t.start()
t2 = threading.Thread(target = fun2)
t2.start()

但是它只打印1个.如何使打印件交错显示?

But it keeps printing just 1's. How can I intercale the prints?

推荐答案

它工作正常，只是打印速度太快而无法看到.尝试在两个函数中都放一个time.sleep()(少量)以使线程休眠那么长的时间，以便实际上可以同时看到1和2.

It is working fine, its just that its printing too fast for you to see . Try putting a time.sleep() in both functions (a small amount) to sleep the thread for that much amount of time, to actually be able to see both 1 as well as 2.

示例-

import threading
import time
sem = threading.Semaphore()

def fun1():
    while True:
        sem.acquire()
        print(1)
        sem.release()
        time.sleep(0.25)

def fun2():
    while True:
        sem.acquire()
        print(2)
        sem.release()
        time.sleep(0.25)

t = threading.Thread(target = fun1)
t.start()
t2 = threading.Thread(target = fun2)
t2.start()

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