Lazy method decorator that allows you to cache the results of function calls with unhashable arguments.

lazy_method.py

class lazy_method(object):
    """ Allows you to cache unhashable arguments. """
    @classmethod
    def truncate(cls, obj):
        """ Removes method cache from obj. """
        if hasattr(obj, '_lazy_items'):
            del obj._lazy_items

    def __init__(self, f):
        def wrapped(self, *args, **kwargs):
            if not hasattr(self, '_lazy_items'):
                self._lazy_items = []
            packed = (f.__name__, args, kwargs)
            try:
                result = next(v for k, v in self._lazy_items if k == packed)
            except StopIteration:
                result = f(self, *args, **kwargs)
                self._lazy_items.append((packed, result))
            return result
        wrapped.__name__ = f.__name__
        self.function = wrapped

    def __call__(self, *args, **kwargs):
        return self.function(*args, **kwargs)

    def __get__(self, obj, obj_type):
        return partial(self.__call__, obj)