TypeError: Fraction.__str__() missing 1 required positional argument: 'self'

Question

错误：

TypeError: Fraction.__str__() missing 1 required positional argument: 'self'

代码：

class Fraction:

    def __init__(self, numerator, denominator):
        self.n = numerator
        self.d = denominator

    def __str__(self):
        return f'{self.n}/{self.d}'

    __repr__ = __str__()

    def __add__(self, other):  # adding the numbers
        n = self.n * other.d + self.d * other.n
        d = self.d * other.d
        return Fraction(n, d)  # object at 0x000001F5E5E6BEB0 memory of the location object

Answer 1

您正在尝试调用__str__并将其返回值分配给__repr__ 。 您想要分配 function 本身：

__repr__ = __str__

但是， __repr__通常应该返回类似于 Python 的代码，可用于重建值，不一定与__str__相同的值。 考虑一下：

class Fraction:

    def __init__(self, numerator, denominator):
        self.n = numerator
        self.d = denominator

    def __str__(self):
        return f'{self.n}/{self.d}'

    def __repr__(self):
        return f'Fraction({self.n}, {self.d})'

    def __add__(self, other):
        n = self.n * other.d + self.d * other.n
        d = self.d * other.d
        return Fraction(n, d)