python线程join方法原理解析

import threading,time

def func():
  print "start thread time: ",time.strftime('%H:%M:%S')
  time.sleep(3)
  print "stop thread time: ",time.strftime('%H:%M:%S')

thread_list = []
for i in range(3):
  t1 = threading.Thread(target=func)
  #t1.setDaemon(True)

  thread_list.append(t1)

for r in thread_list:
  r.start()

for t in thread_list:
  #t.join(1)
  t.join()
print "stop main thread"

###子线程如果设置了t.join(timeout)，则根据timeout的不同，结果会不同，前提是设置了setDaemon(True)，否则join的timeout是没效的

#设置了setDaemon(True),但是没设置t.join()的运行结果:
#start thread time: 17:25:29
#start thread time: 17:25:29
#start thread time: 17:25:29
#stop main thread

#加了t1.setDaemon(True),并且设置了超时时间t.join(1)的运行结果:
#start thread time: 17:12:24
#start thread time: 17:12:24
#start thread time: 17:12:24
#stop main thread

#没加t1.setDaemon(True),并且设置了超时时间t.join(1)的运行结果,不过因为setDaemon的参数不是True所以就算设置了超时时间也没用:
#start thread time: 17:13:28
#start thread time: 17:13:28
#start thread time: 17:13:28
#stop main thread
#stop thread time:  17:13:31
#stop thread time:  17:13:31
#stop thread time:  17:13:31

#没加t1.setDaemon(True),但是设置了t.join(),没有超时时间的阻塞的运行结果:
#start thread time: 17:16:12
#start thread time: 17:16:12
#start thread time: 17:16:12
#stop thread time:  17:16:15
#stop thread time:  17:16:15
#stop thread time:  17:16:15
#stop main thread 

#即没有设置setDaemon(True),也没有设置join()的运行结果:
#start thread time: 17:22:25
#start thread time: 17:22:25
#start thread time: 17:22:25
#stop main thread
#stop thread time:  17:22:28
#stop thread time:  17:22:28
#stop thread time:  17:22:28