template_method.py

#!/usr/bin/env python

import tornado.ioloop
import tornado.web
import functools


class template_method(object):
    _methods = []

    def __init__(self, _method):
        self._methods.append(_method)

    @staticmethod
    def _get_method(handler, method):
        if isinstance(method, property):
            method = method.fget
            value = method(handler)
        else:
            value = functools.partial(method, handler)
        return (method.__name__, value)

    @classmethod
    def get_methods(cls, handler):
        return dict(cls._get_method(handler, m) for m in cls._methods)


class BaseHandler(tornado.web.RequestHandler):
    # Override render_string, passing in additional methods
    def render_string(self, *args, **kwargs):
        template_kwargs = template_method.get_methods(self)
        template_kwargs.update(kwargs)
        return tornado.web.RequestHandler.render_string(
            self, *args, **template_kwargs)

    # Define methods available to handlers that subclass BaseHandler
    @template_method
    def reverse(self, text):
        return text[::-1]

    # Can be used in conjuction with a @property decorator
    @template_method
    @property
    def site_name(self):
        return "My site name"


"""template.html:
{{ reverse("My string") }}
"""

class MainHandler(BaseHandler):
    def get(self):
        # Output: gnirts yM
        self.render("template.html")


class OtherHandler(BaseHandler):
    def get(self):
        # Predefined methods can be overridden
        # Output: My string
        self.render("template.html", reverse=lambda s: s)


if __name__ == "__main__":
    application = tornado.web.Application([
        (r"/", MainHandler),
        (r"/other", OtherHandler)
    ])
    application.listen(8888)
    tornado.ioloop.IOLoop.instance().start()