Is there a better way to do get/set periodically in tornado?

Question

I use global variable to fit my need:

scores = {}

def update():
    global scores
    # fetch data from database
    scores = xxx

class MyRequestHandler(tornado.web.RequestHandler):
    @tornado.web.asynchronous
    def get(self):
        def choice_with_score(items):
            # return a key related to scores
            return key

        def get_key():
            global scores
            return choice_with_score(scores)

        self.write('%s' % get_key())
        self.finish()

if __name__ == '__main__':
    # initially update
    update()

    app = tornado.web.Application([
        (r'.*', MyRequestHandler),
    ])

    http_server = tornado.httpserver.HTTPServer(app)
    http_server.listen(port)
    ioloop = tornado.ioloop.IOLoop.instance()

    # background update every x seconds
    task = tornado.ioloop.PeriodicCallback(
            update,
            15 * 1000)
    task.start()

    ioloop.start()

Here,function update() to get new data instead of updating in every incoming request,so I use global variable.

Is there other ways to do the same work?