python类与对象各个算数运算魔法方法总结

1、python类与对象各个算术运算魔法方法总结：

2、各个魔法方法应用举例:

 

 

3、实例训练：

（1）我们都知道在 Python 中，两个字符串相加会自动拼接字符串，但遗憾的是两个字符串相减却抛出异常。因此，现在我们要求定义一个 Nstr 类，支持字符串的相减操作：A – B，从 A 中去除所有 B 的子字符串。

class Nstr(str):

    def __sub__(self,other):

        self=list(self)

        other=list(other)

        for i in other:

            c=len(self)

            while(c>0):

                if i in self:

                    self.remove(i)

                c=c-1

        x=""

        for j in range(len(self)):

            x=x+self[j]

        return x

a = Nstr('I love iiiiii FishC.com!iiiiiiii')

b = Nstr('i')

print(a-b)

（2）定义一个类 Nstr，当该类的实例对象间发生的加、减、乘、除运算时，将该对象的所有字符串的 ASCII 码之和进行计算：

class Nstr(str):

    def __add__(self,other):

        y=0

        z=0

        for i in self:

            x=ord(i)

            y=y+x

        for j in other:

            q=ord(j)

            z=z+q

        return int(y)+int(z)

    def __sub__(self,other):

        y=0

        z=0

        for i in self:

            x=ord(i)

            y=y+x

        for j in other:

            q=ord(j)

            z=z+q

        return int(y)-int(z)

    def __mul__(self,other):

        y=0

        z=0

        for i in self:

            x=ord(i)

            y=y+x

        for j in other:

            q=ord(j)

            z=z+q

        return int(y)*int(z)

    def __truediv__(self,other):

        y=0

        z=0

        for i in self:

            x=ord(i)

            y=y+x

        for j in other:

            q=ord(j)

            z=z+q

        return int(y)/int(z)

    def __floordiv__(self,other):

        y=0

        z=0

        for i in self:

            x=ord(i)

            y=y+x

        for j in other:

            q=ord(j)

            z=z+q

        return int(y)//int(z)