Calculator in python using class

class cal():

    def __init__(self,a,b):

        self.a=a

        self.b=b

    def add(self):

        return self.a+self.b

    def mul(self):

        return self.a*self.b

    def div(self):

        return self.a/self.b

    def sub(self):

        return self.a-self.b

a=int(input("Enter first number: "))

b=int(input("Enter second number: "))

obj=cal(a,b)

choice=1

while choice!=0:

    print("0. Exit")

    print("1. Add")

    print("2. Subtraction")

    print("3. Multiplication")

    print("4. Division")

    choice=int(input("Enter choice: "))

    if choice==1:

        print("Result: ",obj.add())

    elif choice==2:

        print("Result: ",obj.sub())

    elif choice==3:

        print("Result: ",obj.mul())

    elif choice==4:

        print("Result: ",round(obj.div(),2))

    elif choice==0:

        print("Exiting!")

    else:

        print("Invalid choice!!")

 

 

print()