Thread safe descriptor that combines memoizing (caching) and lazy loading

lazycacheddescriptor.py

class LazyCachedDescriptor(object):
    def __init__(self, fn, *args, **kwargs):
        self.cache = None
        self.fn = fn
        self.args = args
        self.kwargs = kwargs

    def __get__(self, obj, objtype):
        if self.cache is None:
            result = [self.fn(*self.args, **self.kwargs)]
            self.cache = result
        return self.cache[0]

    def reset(self):
        self.cache = None

def func(*args, **kwargs):
    print "func() was called with %s and %s" % (args, kwargs)
    return "func() returned foo"

class consts(object):
    FOO = LazyCachedDescriptor(func, 1, 'foo', b=3)

    @classmethod
    def reset(cls, attrib_name):
        cls.__dict__[attrib_name].reset()


print consts.FOO
print consts.FOO
consts.reset('FOO')
print consts.FOO
print consts.FOO