motor_present_op.py

class MessagesHandler(tornado.web.RequestHandler):
    @tornado.web.asynchronous
    @tornado.gen.engine
    def get(self):
        db = self.settings['db']
        rb = []
        cursor = db.messages.find().sort([('_id', -1)])
        messages = yield motor.Op(cursor.to_list, length=50)
        while messages:
            [rb.append({'id': m['_id'], 'msg': m['msg']}) for m in messages]
            messages = yield motor.Op(cursor.to_list, length=50)
        self.finish({"data": rb})