rationals.py

class Rational(object):

    def __init__(self, num, den):
        self.num = num
        self.den = den

    def __add__(self, other):
        if isinstance(other, int):
            num = self.num + other * self.den
            den = self.den
        elif isinstance(other, Rational):
            num = self.num * other.den + other.num * self.den
            den = self.den * other.den
        else:
            raise TypeError
        return Rational(num, den).simplify()

    def __div__(self, other):
        if isinstance(other, int):
            num = self.num
            den = self.den * other
        elif isinstance(other, Rational):
            num = self.num * other.den
            den = self.den * other.num
        else:
            raise TypeError
        return Rational(num, den).simplify()

    def __mul__(self, other):
        if isinstance(other, int):
            num = self.num * other
            den = self.den
        elif isinstance(other, Rational):
            num = self.num * other.num
            den = self.den * other.den
        else:
            raise TypeError
        return Rational(num, den).simplify()

    def __str__(self):
        if self.den == 1:
            return str(self.num)
        else:
            return '{}/{}'.format(self.num, self.den)

    def simplify(self):
        if self.num % self.den == 0:
            return Rational(self.num / self.den, 1)
        else:
            return self
        

if __name__ == '__main__':
    a = Rational(1,2)
    b = Rational(1,2)
    print(a + 2)