Latest memoize

memoize.py

import functools
import cPickle

from django.conf import settings

# shamelessly stolen from
# http://wiki.python.org/moin/PythonDecoratorLibrary?action=recall&rev=111#Memoize
class memoize(object):
    '''Decorator. Caches a function's return value each time it is called.
    If called later with the same arguments, the cached value is returned 
    (not reevaluated).
    '''

    cache = {}
    pickle_cache = {}

    @classmethod
    def clear(cls):
        cls.cache = {}
        cls.pickle_cache = {}

    def __init__(self, func):
        self.func = func
        self.cache_prefix = (func,)

    def __call__(self, *args, **kwargs):
        if not getattr(settings, "MEMOIZE", True):
            return self.func(*args, **kwargs)

        if not kwargs:
            key = (self.cache_prefix, args) 
            
            try:
                return self.cache[key]
            except KeyError:
                value = self.func(*args)
                self.cache[key] = value
                return value
            except TypeError:
                # unhashable -- for instance, passing a list or dict as an argument.
                # fall through to using pickle
                pass
        try: 
            key = (self.cache_prefix, cPickle.dumps(args, 1), cPickle.dumps(kwargs, 1))
        except TypeError, e:
            # probably have a function being passed in
            return self.func(*args, **kwargs)

        try:
            return self.pickle_cache[key]
        except KeyError:
            value = self.func(*args, **kwargs)
            self.pickle_cache[key] = value
            return value

    def __repr__(self):
        '''Return the function's docstring.'''
        return self.func.__doc__
    
    def __get__(self, obj, objtype):
        '''Support instance methods.'''
        self.cache_prefix = (type(object), obj, self.func)
        return functools.partial(self.__call__, obj)