class Goods:
    def __init__(self):
        self.ori_price = 100
        self.discount = 0.8

    @property
    def price(self):
        return self.ori_price * self.discount

    @price.setter
    def price(self, value):
        self.ori_price = value

    @price.deleter
    def price(self):
        delattr(self, 'ori_price')

g = Goods()
print(g.price)
g.price = 200
print(g.price)
del g.price