子类化
Queue可能是最好的方法。这样的事情应该起作用（未经测试）：
def join_with_timeout(self, timeout): self.all_tasks_done.acquire() try: endtime = time() + timeout while self.unfinished_tasks: remaining = endtime - time() if remaining <= 0.0: raise NotFinished self.all_tasks_done.wait(remaining) finally: self.all_tasks_done.release()
