truediv.py

def __truedive__(self,fraction):
        if fraction.numerator == 0:
            print('Cannot  divide by 0')
            exit()
        else:
            return(Fraction(self.numerator*fraction.denominator,self.denominator*fraction.numerator))

学生的出错信息:

a = Fraction(1,2)
>>> b = Fraction(3,4)
>>> a / b
Traceback (most recent call last):
  File "<pyshell#12>", line 1, in <module>
    a / b
TypeError: unsupported operand type(s) for /: 'Fraction' and 'Fraction'

给学生的回答

你的"魔法方法名错了", 应该用__truediv__.

魔法方法名错误的结果就是, python解释器在运行 a/b的时候, 操作符/会找不到对应的魔法方法.