Python 线程 - 如何在单独的线程中重复执行函数? [英] Python threading - How to repeatedly execute a function in a separate thread?

问题描述

我有这个代码:

import threading
def printit():
  print ("Hello, World!")
  threading.Timer(1.0, printit).start()
threading.Timer(1.0, printit).start()

我正在尝试你好，世界！"每秒打印一次，但是当我运行代码时什么也没有发生，这个过程只是保持活动状态.

I am trying to have "Hello, World!" printed every second, however when I run the code nothing happens, the process is just kept alive.

我读过一些帖子，说明这段代码对人们有用.

I have read posts where exactly this code worked for people.

我对在 python 中设置适当的间隔有多么困难感到非常困惑，因为我已经习惯了 JavaScript.我觉得我错过了什么.

I am very confused by how hard it is to set a proper interval in python, since I'm used to JavaScript. I feel like I'm missing something.

感谢帮助.

推荐答案

我认为您当前的方法没有任何问题.它在 Python 2.7 和 3.4.5 中都对我有用.

I don't see any issue with your current approach. It is working for me me in both Python 2.7 and 3.4.5.

import threading

def printit():
    print ("Hello, World!")
    # threading.Timer(1.0, printit).start()
    #  ^ why you need this? However it works with it too

threading.Timer(1.0, printit).start()

打印:

Hello, World!
Hello, World!

但我建议以以下方式启动线程:

But I'll suggest to start the thread as:

thread = threading.Timer(1.0, printit)
thread.start()

以便您可以使用以下方法停止线程:

So that you can stop the thread using:

thread.cancel()

没有对象Timer 类，您必须关闭解释器才能停止线程.

Without having the object to Timer class, you will have to shut your interpreter in order to stop the thread.

替代方法:

我个人更喜欢通过扩展来编写计时器线程Thread 类为:

Personally I prefer to write a timer thread by extending Thread class as:

from threading import Thread, Event

class MyThread(Thread):
    def __init__(self, event):
        Thread.__init__(self)
        self.stopped = event

    def run(self):
        while not self.stopped.wait(0.5):
            print("Thread is running..")

然后用 Event 的对象启动线程 类为:

my_event = Event()
thread = MyThread(my_event)
thread.start()

您将开始在屏幕上看到以下输出:

You'll start seeing the below output in the screen:

Thread is running..
Thread is running..
Thread is running..
Thread is running..

要停止线程，执行:

my_event.set()

这为将来修改更改提供了更大的灵活性.

This provides more flexibility in modifying the changes for the future.

这篇关于Python 线程 - 如何在单独的线程中重复执行函数?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！