Version of @memoize decorator which works with redis backend.

memoize.py

# -*- coding: utf-8 -*-
from functools import partial
from redis import Redis
import settings

redis_client = Redis(host=settings.REDIS_HOST, port=settings.REDIS_PORT,
                     db=settings.REDIS_DB)


class memoize(object):
    """cache the return value of a method

    Author: Daniel Miller, 
    http://code.activestate.com/recipes/577452-a-memoize-decorator-for-instance-methods/
    This class is meant to be used as a decorator of methods. The return value
    from a given method invocation will be cached on the instance whose method
    was invoked. All arguments passed to a method decorated with memoize must
    be hashable.

    If a memoized method is invoked directly on its class the result will not
    be cached. Instead the method will be invoked like a static method:
    class Obj(object):
        @memoize
        def add_to(self, arg):
            return self + arg
    Obj.add_to(1) # not enough arguments
    Obj.add_to(1, 2) # returns 3, result is not cached
    """

    def __init__(self, func, foo=None):
        self.func = func

    def __get__(self, obj, objtype=None):
        if obj is None:
            return self.func
        return partial(self, obj)

    def __call__(self, *args, **kw):
        obj = args[0]

        try:
            cache = obj.__cache
        except AttributeError:
            cache = obj.__cache = {}
        key = (self.func, args[1:], frozenset(kw.items()))
        try:
            res = cache[key]
        except KeyError:
            res = cache[key] = self.func(*args, **kw)
        return res


class redis_memoize(memoize):
    def __call__(self, *args, **kw):
        obj = args[0]

        if hasattr(self, "__prefix__"):
            prefix = self.__prefix__
        else:
            prefix = "%s.%s.%s" % (obj.__class__.__name__,
                                   obj.__module__,
                                   self.func.__name__)

        key = (prefix, args[1:], tuple(frozenset(kw.items())))

        if redis_client.exists(key):
            res = redis_client.get(key)
        else:
            res = self.func(*args, **kw)
            redis_client.set(key, res)

        return res