建立分数类fraction

好的，下面是一个简单的分数类 `Fraction` 的实现：

class Fraction:
    def __init__(self, numerator, denominator=1):
        if denominator == 0:
            raise ZeroDivisionError("Denominator cannot be zero.")
        self.numerator = numerator
        self.denominator = denominator

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

    def __repr__(self):
        return f"Fraction({self.numerator}, {self.denominator})"

    def __eq__(self, other):
        if isinstance(other, Fraction):
            return self.numerator * other.denominator == self.denominator * other.numerator
        elif isinstance(other, int):
            return self.numerator == other * self.denominator
        else:
            return NotImplemented

    def __lt__(self, other):
        if isinstance(other, Fraction):
            return self.numerator * other.denominator < self.denominator * other.numerator
        elif isinstance(other, int):
            return self.numerator < other * self.denominator
        else:
            return NotImplemented

    def __le__(self, other):
        if isinstance(other, Fraction):
            return self.numerator * other.denominator <= self.denominator * other.numerator
        elif isinstance(other, int):
            return self.numerator <= other * self.denominator
        else:
            return NotImplemented

    def __add__(self, other):
        if isinstance(other, Fraction):
            return Fraction(self.numerator * other.denominator + other.numerator * self.denominator, self.denominator * other.denominator)
        elif isinstance(other, int):
            return Fraction(self.numerator + other * self.denominator, self.denominator)
        else:
            return NotImplemented

    def __sub__(self, other):
        if isinstance(other, Fraction):
            return Fraction(self.numerator * other.denominator - other.numerator * self.denominator, self.denominator * other.denominator)
        elif isinstance(other, int):
            return Fraction(self.numerator - other * self.denominator, self.denominator)
        else:
            return NotImplemented

    def __mul__(self, other):
        if isinstance(other, Fraction):
            return Fraction(self.numerator * other.numerator, self.denominator * other.denominator)
        elif isinstance(other, int):
            return Fraction(self.numerator * other, self.denominator)
        else:
            return NotImplemented

    def __truediv__(self, other):
        if isinstance(other, Fraction):
            return Fraction(self.numerator * other.denominator, self.denominator * other.numerator)
        elif isinstance(other, int):
            return Fraction(self.numerator, self.denominator * other)
        else:
            return NotImplemented

这个类支持分数的加、减、乘、除运算，以及比较运算符 `<`, `<=`, `==`。注意到我们在实现运算符方法时，对于可能出现的类型不匹配情况，我们返回了 `NotImplemented`，这是为了让 Python 解释器知道我们没有实现这种情况下的运算，从而让它去尝试反向调用运算符方法。例如，如果 `a` 是一个分数，`b` 是一个整数，那么 `a + b` 会先尝试调用 `a.__add__(b)`，如果返回了 `NotImplemented`，则会尝试调用 `b.__radd__(a)`。如果 `b` 也没有实现 `__radd__` 方法，那么就会抛出 `TypeError` 异常。