当父线程退出时，Python守护进程线程不会退出 [英] Python daemon thread does not exit when parent thread exits

问题描述

我有一些创建恶魔线程的Python代码.父线程几乎立即结束，但守护程序线程保持打印睡眠状态.

I have some Python code that creates a demon thread. The parent thread ends almost immediately, but the daemon thread keeps printing sleep.

import threading
import time
def int_sleep():
    for _ in range(1, 600):
        time.sleep(1)
        print("sleep")

def main():
    thread = threading.Thread(target=int_sleep)
    thread.daemon = True
    thread.start()
    time.sleep(2)
    print("main thread end...")

thread = threading.Thread(target=main)
thread.start()

sys.version:

sys.version:

'3.3.3 (v3.3.3:c3896275c0f6, Nov 18 2013, 21:19:30) [MSC v.1600 64 bit (AMD64)]'

打印:

sleep

main thread end...

sleep

sleep

sleep

为什么父线程退出时Python守护进程线程不退出?

Why doesn't the Python daemon thread exit when parent thread exits?

推荐答案

如果为python线程指定thread.daemon = True，则仅保留守护程序时，程序将立即停止.发送到标准输出的命令将丢失.

If you specify thread.daemon = True for your python thread, then the program will halt immediately when only the daemon is left. The the commands sent to stdout are lost.

将此添加到名为main.py的文件中

Add this to a file called main.py

import threading
import time

def int_sleep():
  for _ in range(1, 600):
    time.sleep(1)
    print("sleep")

def main():
  thread = threading.Thread(target=int_sleep)
  thread.daemon = True
  thread.start()
  time.sleep(2)
  print("main thread end...")

thread = threading.Thread(target=main)
thread.daemon = True
thread.start()

像这样运行它:

el@apollo:~/code/python/run01$ python --version
Python 2.7.6
el@apollo:~$ python main.py 
el@apollo:~$

看到它不打印任何内容，因为线程已启动.您将其设置为守护程序并启动它.然后程序结束.

See it prints nothing because the thread started. You set it to be a daemon and started it. Then the program ended.

附加说明:如果将此代码粘贴到python解释器中，则所有打印语句将出现在终端上，因为守护程序永远不会失去与stdout的连接.

Extra notes: If you paste this code into a python interpreter, all the print statements will appear on the terminal because the daemon never loses hold of its connection to stdout.

了解更多: http://docs.python.org/2/library/threading .html

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