当父线程退出时，Python守护线程不会退出(Python daemon thread does not exit when parent thread exits)

我有一些创建恶魔线程的Python代码。父线程几乎立即结束，但守护线程继续打印睡眠。

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()

内容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

为什么当父线程退出时，Python守护进程线程不会退出？

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:

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

Prints:

sleep main thread end... sleep sleep sleep

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

最满意答案

如果你为python线程指定了thread.daemon = True ，那么当只有守护进程被留下时，程序会立即停止。发送到stdout的命令会丢失。

将其添加到名为main.py的文件中

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:~$

看到它没有打印任何东西，因为线程开始您将其设置为守护进程并启动它。然后程序结束。

附加说明：如果将此代码粘贴到python解释器中，则所有打印语句都将显示在终端上，因为守护进程永远不会丢失与stdout的连接。

阅读更多： http : //docs.python.org/2/library/threading.html

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.

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()

Run it like this:

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

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

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.

Read more: http://docs.python.org/2/library/threading.html

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