一、知识梳理：

二、货币场景搭建：

1）代码展示：

class RMB:
    count = 0
    def __init__(self,yuan=0,jiao=0,fen=0):
        self.__yuan = yuan
        self.__jiao = jiao
        self.__fen = fen
        RMB.count += 1

    def __add__(self, other):
        temp = RMB()
        temp.__yuan = self.__yuan + other.__yuan
        temp.__jiao = self.__jiao + other.__jiao
        temp.__fen = self.__fen + other.__fen
        return temp

    def __sub__(self, other):
        temp = RMB()
        temp.__yuan = self.__yuan - other.__yuan
        temp.__jiao = self.__jiao - other.__jiao
        temp.__fen = self.__fen - other.__fen
        return temp

    def __gt__(self, other):
        if self.__yuan > other.__yuan:
            return True
        elif (self.__yuan == other.__yuan) and self.__jiao > other.__jiao:
            return True
        elif ((self.__yuan == other.__yuan) and (self.__jiao == other.__jiao)) and self.__fen > other.__fen:
            return True
        else:
            return False

    def __isub__(self, other=0):
        self.__yuan -= 1
        self.__jiao -= 1
        self.__fen -= 1

    def __iadd__(self, other=0):
        self.__yuan += 1
        self.__jiao += 1
        self.__fen += 1

    def __del__(self):
        RMB.count -= 1

    def __str__(self):
        return f"{self.__yuan}元{self.__jiao}角{self.__fen}分,count={RMB.count}"

if __name__ == '__main__':
    x = RMB(5,5,5)
    print(f"x={x}")
    y = RMB(3,3,3)
    print(f"y={y}")
    z = x + y
    print(f"x+y={z}")
    w = x - y
    print(f"x-y={w}")
    print(f"x > y的结果是{x > y}")
    x.__isub__()
    print(f"x自减之后,x={x}")
    y.__iadd__()
    print(f"y自增之后,y={y}")

 2）结果展示：

x=5元5角5分,count=1
y=3元3角3分,count=2
x+y=8元8角8分,count=3
x-y=2元2角2分,count=3
x > y的结果是True
x自减之后,x=4元4角4分,count=3
y自增之后,y=4元4角4分,count=3