python - python线程的问题

Question

这个程序有两个线程，这个程序运行一段时间后，只有一个线程打印出myid，为什么？另一个头有什么问题？

from threading import Thread  
from time import sleep  

class MyThread(Thread):  
      def __init__(self,myid):  
          Thread.__init__(self)  
          self.myid = myid  
          print self.myid  
      def run(self):  
          flag = True  
          while flag:  
              try:  
                  print self.myid  
                  sleep(0.1)  
              except Exception,e:  
                  print e  
                  flag = False  


if __name__ =="__main__":  
      threads = []  
      for i in range(1,3):  
          t = MyThread(i)  
          threads.append(t)  
      for t in threads:  
          t.start()  
      threads[0].join()  
      print '1 is finished'  
      threads[1].join()  
      print '2 is finished'  
      print 'All finished'