Python线程，Event和Queue如何协同工作？

Question

在看了比斯利书中的例子后，我正在和我的朋友交谈

class ActorExit(Exception):
    pass

class Actor:
    def __init__(self):
        self._mailbox = Queue()

    def send(self, msg):
        self._mailbox.put(msg)

    def recv(self):
        msg = self._mailbox.get()
        if msg is ActorExit:
            raise ActorExit()
        return msg

    def close(self):
        self.send(ActorExit)

    def start(self):
        self._terminated = Event()
        t = Thread(target=self._bootstrap)
        t.daemon = True
        t.start()

    def _bootstrap(self):
        try:
            self.run()
        except ActorExit:
            pass
        finally:
            self._terminated.set()

    def join(self):
        self._terminated.wait()

    def run(self):
        while True:
            msg = self.recv()

class PrintActor(Actor):
    def run(self):
        while True:
            msg = self.recv()
            print('Got:', msg)

我的朋友认为 Event 的唯一目的是阻塞主线程，直到另一个线程执行设置操作。真的吗？我们如何观察线程执行？