Get/set with cache (needs decorator)

getset.py

@property
def cached_foo(self):
    try:
        return self._cache[foo]
    except AttributeError:
        self._cache = {}
        self._cache[foo] = calculate_foo()
    except KeyError:
        self._cache[foo] = calculate_foo()
    return self._cache[foo]

@cached_foo.setter
def cached_foo(self, bar):
    try:
        self._cache[foo] = bar
    except AttributeError:
        self._cache = {}
    self._cache[foo] = bar