Weirdest memoize decorator in world (modified version of http://code.activestate.com/recipes/577452-a-memoize-decorator-for-instance-methods/ by Daniel Miller)

memoize_decorator.py

# -*- coding: utf-8 -*-
from functools import wraps, partial

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

    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(cache_key="foobar")
        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, cache_key=None):
        self.cache_key = cache_key

    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]

        if not hasattr(self, "func"):
            self.func = obj
            return self

        try:
            cache = obj.__cache
        except AttributeError:
            cache = obj.__cache = {}

        key = (self.cache_key, self.func, args[1:], frozenset(kw.items()))
        print(key)

        try:
            res = cache[key]
        except KeyError:
            res = cache[key] = self.func(*args, **kw)
        return res