之前用多线程的时候看见了很多文章，比较常用的大概就是join()和setDeamon()了。
先说一下自己对join()的理解吧：
def join(self, timeout=None):
"""Wait until the thread terminates. This blocks the calling thread until the thread whose join() method is
called terminates -- either normally or through an unhandled exception
or until the optional timeout occurs. When the timeout argument is present and not None, it should be a
floating point number specifying a timeout for the operation in seconds
(or fractions thereof). As join() always returns None, you must call
isAlive() after join() to decide whether a timeout happened -- if the
thread is still alive, the join() call timed out. When the timeout argument is not present or None, the operation will
block until the thread terminates. A thread can be join()ed many times. join() raises a RuntimeError if an attempt is made to join the current
thread as that would cause a deadlock. It is also an error to join() a
thread before it has been started and attempts to do so raises the same
exception. """
源码的__doc__其实说的很清楚，join()会阻塞调用该线程的线程，知道该线程结束（This blocks the calling thread
until the thread whose join() method is called terminates）。
注意点：
#coding:utf-8
import threading
import time def action(arg):
time.sleep(1)
print 'sub thread start!the thread name is:%s ' % threading.currentThread().getName()
print 'the arg is:%s ' %arg
time.sleep(1) #不正确写法，会导致多线程顺序执行，失去了多线程的意义
for i in xrange(4):
t =threading.Thread(target=action,args=(i,))
t.setDaemon(True)
t.start()
t.join() #正确写法
thread_list = [] #线程存放列表
for i in xrange(4):
t =threading.Thread(target=action,args=(i,))
t.setDaemon(True)
thread_list.append(t) for t in thread_list:
t.start() for t in thread_list:
t.join() print 'main_thread end!'
下面再说一下setDeamon()吧：
其实主线程并不会结束setDeamon(True)的线程，而是当主线程执行完毕之后不会再去关注setDeamon(True)的线程。
所以setDeamon(True)的线程的结果是我们无法获取到的，类似于爱咋咋地？不管你输出什么，我都不看，主线程跑
完就结束整个python process。
而setDeamon(False)的线程会一直受到主线程的关注，就算主线程跑完了也会等setDeamon(False)的线程跑完然后
再结束整个python process。
所以说，就算setDeamon(True)的线程在主线程之后跑完，但如果在setDeamon(False)的线程之前跑完的话，也是会
输出结果的，而不是被所谓的主线程结束就杀死setDeamon(False)的线程。
附上我的调试代码，
# -*- coding:utf-8 -*- import threading
import time stime = time.time() def action(arg):
time.sleep(1)
print ('the arg is:%s,time is %s ' % (arg, time.time())) def action1(arg):
time.sleep(1)
print ('the arg is:%s,time is %s ' % (arg, time.time())) thread_list = [] # 线程存放列表
for i in [777, 888]:
t = threading.Thread(target=action, args=(i,))
t.setDaemon(False)
thread_list.append(t)
for i in range(10):
t = threading.Thread(target=action1, args=(i,))
t.setDaemon(True)
thread_list.append(t) for t in thread_list:
t.start() print('**************')
etime = time.time()
print('time cost is %s' % (etime - stime))