Rational Class

from math import gcd
class Rational:
    def __init__(self):
        self.__p = 0
        self.__q = 1

    def set(self, p, q):
        self.__p = p
        if q == 0:
            q = 1
        self.__q = q

    def __str__(self):
        if self.__p>0 and self.__q<0:
            self.__p=-self.__p
            self.__q=-self.__q
            return f'{str(self.__p)}/{str(self.__q)}'
        elif self.__p<0 and self.__q<0:
            self.__p=-self.__p
            self.__q=-self.__q
            return f'{str(self.__p)}/{str(self.__q)}'
        else:
            return f'{str(self.__p)}/{str(self.__q)}'

    def __eq__(self, obj):
        return self.__p == obj.__p and self.__q == obj.__q

    def __sub__(self, obj):
        new_object = Rational()
        new_object.__q = self.__q * obj.__q
        new_object.__p = (self.__p * obj.__q) - (self.__q * obj.__p)
        return new_object
    def __add__(self, obj):
        new_object = Rational()
        new_object.__q = self.__q * obj.__q
        new_object.__p = (self.__p * obj.__q) + (self.__q * obj.__p)
        return new_object
    def __mul__(self, obj):
        new_object = Rational()
        new_object.__q = self.__q * obj.__q
        new_object.__p = (self.__p * obj.__q) * (self.__q * obj.__p)
        return new_object
    def __gt__(self,obj):
        if (self.__p / self.__q) > (obj.__p /obj.__q):
            return True
        else:
            return False
    def __lt__(self,obj):
        if (self.__p / self.__q) < (obj.__p /obj.__q):
            return True
        else:
            return False
    def normalize(self):
        d=gcd(self.__p,self.__q)
        self.__p=int(self.__p / d)
        self.__q=int(self.__q / d)
        return self.__p , self.__q

def main():
    r1 = Rational()
    r2 = Rational()
    r3 = Rational()
    r1.set(36,12)
    print(r1)
    print(r1.normalize())
    r2.set(21,7)
    r3.set(9,3)
    print(r2)
    print(r2.normalize())
    print(r3)
    print(r3.normalize())
    if r1 == r2:
        print ('Both are equal')
    if r1 == r3:
        print ('Both are equal')
    else:
        print ('Both are different')
    print(r1 > r2)
    print(r1 > r3)
    r4 = r1 - r3
    r5=r1 * r3
    print(r4)
    print(r5)

main()