How to make one connection to SQLite db for whole tornado web application?

Now I am creating new connection to SQLite db each time I edit username. What should I do to make a single connection for a whole application?

class UserEditHandler(tornado.web.RequestHandler):
    def get(self, user_id):
        self.render('user_edit.html')

    def post(self, user_id):
        edited_name = str(self.get_arguments('name')[0])
        session = create_session()
        user_object = session.query(User).filter_by(id=user_id).first()
        user_object.name = edited_name
        session.commit()