Cached Property

cached_property.py

def cached_property(func):
    property_name = '_' + func.__name__
    @functools.wraps(func)
    def wrapped(self, *args, **kwargs):
        private_property = getattr(self, property_name, None)
        if kwargs.get('force', False) or private_property == None:
            val = func(self, *args, **kwargs)
            setattr(self, property_name, val)
            return val
        else:
            return private_property
    return property(wrapped)