python threading中的join和setDaemon方法

python 多线程的threading中的join和setDaemon方法

join():通俗的将就是阻止子线程随着主线程的结束而结束

setDaemon()：设置子线程是否随着主线程的结束而结束， 其中：

setDaemon(True) : 设置子线程随着主线程的结束而结束

setDaemon(False) 等价于join() :设置子线程不随着主线程的结束而结束

修改http://blog.csdn.net/sjyu_ustc/article/details/71080834代码如下：

#!/usr/bin/python# -*- coding: utf-8 -*-import threading,timedef test(loop, sec):    print 'start loop', loop, 'at:', time.ctime()    time.sleep(sec)    print 'loop', loop, 'done at:', time.ctime()def main():    print 'starting at:', time.ctime()    thpool = []    for i in xrange(10):        th = threading.Thread(target= test,args= (i,2))        th.start()        thpool.append(th)    for th in thpool:        th.join()    print 'all Done at:', time.ctime()if __name__ == '__main__':        main()

结果：

starting at: Tue May  2 14:31:41 2017start loop 0 at: Tue May  2 14:31:41 2017start loop 1 at: Tue May  2 14:31:41 2017start loop 2 at: Tue May  2 14:31:41 2017start loop 3 at: Tue May  2 14:31:41 2017start loop 4 at: Tue May  2 14:31:41 2017start loop 5 at: Tue May  2 14:31:41 2017start loop 6 at: Tue May  2 14:31:41 2017start loop 7 at: Tue May  2 14:31:41 2017start loop 8 at: Tue May  2 14:31:41 2017start loop 9 at: Tue May  2 14:31:41 2017loop 0 done at: Tue May  2 14:31:43 2017loop 1 done at: looploop  4 loopdone at:  Tue May  2 14:31:43 20172Tue May  2 14:31:43 2017 done at: Tue May  2 14:31:43 20173 done at: Tue May  2 14:31:43 2017loop 5 done at: Tue May  2 14:31:43 2017loop 6 done at: Tue May  2 14:31:43 2017loop 7 done at: Tue May  2 14:31:43 2017loop 8 done at: Tue May  2 14:31:43 2017loop 9 done at: Tue May  2 14:31:43 2017all Done at: Tue May  2 14:31:43 2017

可以看出修改前join方法使得每个子线程顺序执行，所有子线程执行完毕后，主线程才退出。 修改后，所有子线程几乎同时执行，之后主线程执行在退出。

修改为setDaemon方法，继续观察：

#!/usr/bin/python# -*- coding: utf-8 -*-import threading,timedef test(loop, sec):    print 'start loop', loop, 'at:', time.ctime()    time.sleep(sec)    print 'loop', loop, 'done at:', time.ctime()def main():    print 'starting at:', time.ctime()    for i in xrange(10):        th = threading.Thread(target= test,args= (i,2))        th.setDaemon(True)        th.start()            print 'all Done at:', time.ctime()if __name__ == '__main__':        main()

结果：

starting at: Tue May  2 14:57:48 2017start loop 0 at: Tue May  2 14:57:48 2017start loop 1 at: Tue May  2 14:57:48 2017start loop 2 at: Tue May  2 14:57:48 2017start loop 3 at: Tue May  2 14:57:48 2017start loop 4 at: Tue May  2 14:57:48 2017start loop 5 at: Tue May  2 14:57:48 2017start loop 6 at: Tue May  2 14:57:48 2017start loop 7 at: Tue May  2 14:57:48 2017start loop 8 at: Tue May  2 14:57:48 2017start loop 9 at:all Done at: Tue May  2 14:57:48 2017 Tue May  2 14:57:48 2017

可以看出子线程都还没执行完，因为主线程退出也都随着主线程退出了

#!/usr/bin/python# -*- coding: utf-8 -*-import threading,timedef test(loop, sec):    print 'start loop', loop, 'at:', time.ctime()    time.sleep(sec)    print 'loop', loop, 'done at:', time.ctime()def main():    print 'starting at:', time.ctime()    for i in xrange(10):        th = threading.Thread(target= test,args= (i,2))        th.setDaemon(False)        th.start()            print 'all Done at:', time.ctime()if __name__ == '__main__':        main()

结果：

starting at: Tue May  2 15:01:46 2017start loop 0 at: Tue May  2 15:01:46 2017start loop 1 at: Tue May  2 15:01:46 2017start loop 2 at: Tue May  2 15:01:46 2017start loop 3 at: Tue May  2 15:01:46 2017start loop 4 at: Tue May  2 15:01:46 2017 start loop 5 at: Tue May  2 15:01:46 2017start loop 6 at: Tue May  2 15:01:46 2017start loop 7 at: Tue May  2 15:01:46 2017start loop 8 at: Tue May  2 15:01:46 2017start loop 9 all Done at: Tue May  2 15:01:46 2017at: Tue May  2 15:01:46 2017loop 0 done at: Tue May  2 15:01:48 2017loop 5 done at: Tue May  2 15:01:48 2017 loop 3 done at:loop 2 done at: Tue May  2 15:01:48 2017 Tue May  2 15:01:48 2017 loop 1 done at: Tue May  2 15:01:48 2017loop 4 done at: Tue May  2 15:01:48 2017loop 6 done at: Tue May  2 15:01:48 2017loop 7 done at: Tue May  2 15:01:48 2017loop 8 done at: Tue May  2 15:01:48 2017loop 9 done at: Tue May  2 15:01:48 2017

设置为false后，主线程退出后，子线程并没随着主线程的退出而退出