guestbook.py 文件源码

def get_messages_async(self):
        @ndb.tasklet
        def callback(msg):
            acct = yield msg.author.get_async()
            raise ndb.Return('On {}, {} wrote:\n{}'.format(
                msg.when, acct.nick(), msg.text))

        qry = Message.query().order(-Message.when)
        outputs = qry.map(callback, limit=20)
        for output in outputs:
            self.response.out.write('<p>{}</p>'.format(output))