python中的守护线程

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守护线程的作用是什么？用两段代码来说明

代码段1：

# -*- coding: utf-8 -*-
import threading
import time


def send_message(mes):
    print "before send message"
    time.sleep(2)
    print "after send message"


def get_message(mes):
    print "before get message"
    time.sleep(2)
    print "after get message"


if __name__ == "__main__":
    thread1 = threading.Thread(target=send_message, args=("",))
    thread2 = threading.Thread(target=get_message, args=("",))
    thread1.start()
    thread2.start()
    print "主线程执行完毕"

当我执行此代码的时候，输出结果如下：而且很明显是在主线程执行完毕后，停留了两秒，程序才终止的。

那么如果想在主线程执行完成后，马上就将子线程干掉该如何做呢？请看如下代码

# -*- coding: utf-8 -*-
import threading
import time


def send_message(mes):
    print "before send message"
    time.sleep(2)
    print "after send message"


def get_message(mes):
    print "before get message"
    time.sleep(2)
    print "after get message"


if __name__ == "__main__":
    thread1 = threading.Thread(target=send_message, args=("",))
    thread2 = threading.Thread(target=get_message, args=("",))
    thread1.setDaemon(True)
    thread2.setDaemon(True)
    thread1.start()
    thread2.start()
    print "主线程执行完毕"

此时当主线程执行完成后，就会立马干掉子线程