如何在Python中实现运算符重载？

class Vector:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def __add__(self, other):
        return Vector(self.x + other.x, self.y + other.y)

    def __str__(self):
        return f"Vector({self.x}, {self.y})"

# 使用示例
v1 = Vector(2, 3)
v2 = Vector(4, 5)
v3 = v1 + v2
print(v3)  # 输出: Vector(6, 8)

class Fraction:
    def __init__(self, numerator, denominator):
        self.numerator = numerator
        self.denominator = denominator
        self._simplify()

    def _simplify(self):
        gcd = self._gcd(self.numerator, self.denominator)
        self.numerator //= gcd
        self.denominator //= gcd
        if self.denominator < 0:
            self.numerator *= -1
            self.denominator *= -1

    @staticmethod
    def _gcd(a, b):
        while b:
            a, b = b, a % b
        return a

    def __add__(self, other):
        new_numerator = self.numerator * other.denominator + other.numerator * self.denominator
        new_denominator = self.denominator * other.denominator
        return Fraction(new_numerator, new_denominator)

    def __mul__(self, other):
        new_numerator = self.numerator * other.numerator
        new_denominator = self.denominator * other.denominator
        return Fraction(new_numerator, new_denominator)

    def __str__(self):
        return f"{self.numerator}/{self.denominator}"

# 使用示例
f1 = Fraction(1, 2)
f2 = Fraction(1, 3)
f3 = f1 + f2
f4 = f1 * f2
print(f3)  # 输出: 5/6
print(f4)  # 输出: 1/6