Method decorator which extends regular property to cache the value.

cached_property.py

class cached_property(object):
    """Decorator that converts a method with a single self argument into a property cached on the instance."""
    def __init__(self, func):
        self._get = func
        self.__doc__ = getattr(func, '__doc__')
        self._name = '_cached_' + func.__name__

    @staticmethod
    def _set(obj, value):
        raise AttributeError("can't set attribute")

    def setter(self, func):
        self._set = func
        return self

    def __get__(self, obj, cls):
        if obj is None:
            return self
        try:
            return obj.__dict__[self._name]
        except KeyError:
            pass
        res = self._get(obj)
        obj.__dict__[self._name] = res
        return res

    def __set__(self, obj, value):
        self._set(obj, value)
        obj.__dict__[self._name] = value

    def __delete__(self, obj):
        try:
            del obj.__dict__[self._name]
        except KeyError:
            raise AttributeError(self._get.__name__)