实现一个简易的Python版CountDownLatch

'''
Created on 2017-1-11

@author: admin
'''
from threading import Condition, Thread
import time

class CountDownLatch:
    def __init__(self,count):
        self.count=count
        self.condition=Condition()
    def await(self):
        try:
            self.condition.acquire()
            while self.count>0:
                self.condition.wait()
        finally:
            self.condition.release()
    def countDown(self):
        try:
            self.condition.acquire()
            self.count-=1
            self.condition.notifyAll()
        finally:
            self.condition.release()
if __name__ == '__main__':
    class SubThread(Thread):
        def __init__(self,name,latch):
            Thread.__init__(self)
            self.name=name;
            self.latch=latch
        def run(self):
            print("finishing %s"%self.name)
            time.sleep(3)
            self.latch.countDown()
            
    latch=CountDownLatch(3)
    print("start main thread")
    thread1=SubThread("thread first",latch)
    thread2=SubThread("thread second",latch)
    thread3=SubThread("thread third",latch)
    thread1.start()
    thread2.start()
    thread3.start()
    latch.await()
    print("stop main thread")