关于python多线程join()

Question

import threading
import time

class Producer(threading.Thread):
    def __init__(self,t_name):
        threading.Thread.__init__(self,name=t_name)

    def run(self):
        global x
        con.acquire()

        if x>0:
            con.wait()
        else:
            for i in xrange(0,5,1):
                x+=1
                print u'producing...'+str(x)
            con.notify()
        print x
        con.release()

class Consumer(threading.Thread):
    def __init__(self,t_name):
        threading.Thread.__init__(self,name=t_name)

    def run(self):
        global x
        con.acquire()

        if x<0:
            con.wait()
        else:
            for i in xrange(0,5,1):
                x-=1
                print u'consume...'+str(x)
            con.notify()
        print x
        con.release()

con = threading.Condition()
x = 0
print u'start consumer'
c = Consumer('consumer')
print u'start producer'
p = Producer('producer')

p.start()
c.start()
p.join()
c.join()

print x

最后的join()函数的有无对程序结果并无显示作用？请问join()在这里意义何在？

Answer 1

不join 主线程结束了你的子线程怎么办

Answer 2

Other threads can call a thread’s join() method. This blocks the calling thread until the thread whose join() method is called is terminated.
Thread Objects
threading.Thread.join
阻塞当前调用 thread.join()的进程或者线程，直到join的线程（ the thread whose join() method is called ）结束，才继续执行当前进程或者线程（the calling thread ）~