Cache decorator and cached property decorator

caching.py

from functools import wraps

def cache(fn):
    cache_dict = {}
    @wraps(fn)
    def result(*args, **kwargs):
        # can't cache kwargs
        assert not kwargs
        if args not in cache_dict:
            cache_dict[args] = fn(*args)
        return cache_dict[args]
    result.cache = cache_dict
    return result

def cached_property(fn=None, allow_set=None):
    if allow_set is not None:
        return lambda f: cached_property(f, allow_set)

    @property
    @wraps(fn)
    def result(self):
        self._property_cache = getattr(self, '_property_cache', {})
        if fn.__name__ not in self._property_cache:
            self._property_cache[fn.__name__] = fn(self)
        return self._property_cache[fn.__name__]

    if allow_set:
        @result.setter
        def result(self, val):
            self._property_cache = getattr(self, '_property_cache', {})
            self._property_cache[fn.__name__] = val

    return result