# coding: utf-8


class Figure(object):
    def stretch_w(self, by):
        raise NotImplementedError()


class Rectangle(Figure):
    def __init__(self, width, height):
        self.width = width
        self.height = height

    def stretch_w(self, by):
        self.width += by


class Square(Rectangle):
    def __init__(self, side):
        self.side = side

    def _to_rect(self):
        new_rect = Rectangle(self.side, self.side)
        self.__class__ = new_rect.__class__
        self.__dict__ = new_rect.__dict__

    def stretch_w(self, by):
        self._to_rect()
        self.stretch_w(by)


if __name__ == "__main__":
    fig = Square(5)
    print(type(fig), fig.__dict__)

    fig.stretch_w(5)
    print(type(fig), fig.__dict__)

    """
    >>> <class '__main__.Square'> {'side': 5}
    >>> <class '__main__.Rectangle'> {'width': 10, 'height': 5}
    """