python 多线程 t.setDaemon(True):

t.setDaemon(True):

#coding=utf-8
import threading
from time import ctime,sleep


def music(func):
    for i in range(5):
        print "I was listening to %s. %s" %(func,ctime())
        #print threading.currentThread()
        sleep(2)

def move(func):
    for i in range(2):
        print "I was at the %s! %s" %(func,ctime())
        #print threading.currentThread()
        sleep(50)

threads = []
t1 = threading.Thread(target=music,args=(u'爱情买卖',))
threads.append(t1)
t2 = threading.Thread(target=move,args=(u'阿凡达',))
threads.append(t2)

if __name__ == '__main__':
    for t in threads:
        t.setDaemon(True)
        t.start()
        #print threading.currentThread()
    print "all over %s" %ctime()


C:Python27python.exe C:/Users/TLCB/PycharmProjects/untitled/mycompany/thread/p7.py
I was listening to 爱情买卖. Thu Sep 07 14:27:02 2017
I was at the 阿凡达! Thu Sep 07 14:27:02 2017
 all over Thu Sep 07 14:27:02 2017

Process finished with exit code 0
----------------------------------------------------------------------------------

#coding=utf-8
import threading
from time import ctime,sleep


def music(func):
    for i in range(5):
        print "I was listening to %s. %s" %(func,ctime())
        #print threading.currentThread()
        sleep(2)

def move(func):
    for i in range(2):
        print "I was at the %s! %s" %(func,ctime())
        #print threading.currentThread()
        sleep(50)

threads = []
t1 = threading.Thread(target=music,args=(u'爱情买卖',))
threads.append(t1)
t2 = threading.Thread(target=move,args=(u'阿凡达',))
threads.append(t2)

if __name__ == '__main__':
    for t in threads:
        #t.setDaemon(True)
        t.start()
        #print threading.currentThread()
    print "all over %s" %ctime()

C:Python27python.exe C:/Users/TLCB/PycharmProjects/untitled/mycompany/thread/p7.py
I was listening to 爱情买卖. Thu Sep 07 14:24:58 2017
I was at the 阿凡达! Thu Sep 07 14:24:58 2017
all over Thu Sep 07 14:24:58 2017
I was listening to 爱情买卖. Thu Sep 07 14:25:00 2017
I was listening to 爱情买卖. Thu Sep 07 14:25:02 2017
I was listening to 爱情买卖. Thu Sep 07 14:25:04 2017
I was listening to 爱情买卖. Thu Sep 07 14:25:06 2017
I was at the 阿凡达! Thu Sep 07 14:25:48 2017

Process finished with exit code 0


　setDaemon(True)将线程声明为守护线程，必须在start() 方法调用之前设置，如果不设置为守护线程程序会被无限挂起。

子线程启动后，父线程也继续执行下去，当父线程执行完最后一条语句print "all over %s" %ctime()后，没有等待子线程，直接就退出了，同时子线程也一同结束。

从执行结果来看，子线程（muisc 、move ）和主线程（print "all over %s" %ctime()）都是同一时间启动，

但由于主线程执行完结束，所以导致子线程也终止。 



一个布尔值表明是否这个线程是一个daemon 线程(True) or not (False).

这个必须是设置在start()被调用前,否则错误会被抛出。

它的初始值是从创建线程中继承而来, 主线程不是一个daemon线程 因此

所有的线程创建在主线程默认 daemon =False



setDaemon()方法。主线程A中，创建了子线程B，并且在主线程A中调用了B.setDaemon(),这个的意思是，把主线程A设置为守护线程，

这时候，要是主线程A执行结束了，就不管子线程B是否完成,一并和主线程A退出.这就是setDaemon方法的含义


主线程退出,不管子线程是否完成,一并退出



但是有时候我们需要的是，只要主线程完成了，不管子线程是否完成，都要和主线程一起退出，这时就可以用setDaemon方法了。