定义一个有理数类。一个有理数类是一个可以表示成两个整数相除的数，如1/2、2/3、4/5。一个有理数类有两个整数成员表示：分子和分母。

好的，以下是一个简单的有理数类的定义：

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

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

    def simplify(self):
        gcd = self._gcd(self.numerator, self.denominator)
        self.numerator //= gcd
        self.denominator //= gcd

    def _gcd(self, a, b):
        if b == 0:
            return a
        return self._gcd(b, a % b)

    def __add__(self, other):
        numerator = self.numerator * other.denominator + other.numerator * self.denominator
        denominator = self.denominator * other.denominator
        return Rational(numerator, denominator)

    def __sub__(self, other):
        numerator = self.numerator * other.denominator - other.numerator * self.denominator
        denominator = self.denominator * other.denominator
        return Rational(numerator, denominator)

    def __mul__(self, other):
        numerator = self.numerator * other.numerator
        denominator = self.denominator * other.denominator
        return Rational(numerator, denominator)

    def __truediv__(self, other):
        numerator = self.numerator * other.denominator
        denominator = self.denominator * other.numerator
        return Rational(numerator, denominator)

这个类有两个成员变量：分子和分母。它还有一个 `__str__` 方法，用于将有理数转换为字符串。它还有一个 `simplify` 方法，用于将有理数化简为最简形式。它还有四个运算符重载方法：`__add__`、`__sub__`、`__mul__` 和 `__truediv__`，用于实现有理数的加、减、乘、除运算。