python calculator

calculator.py

class Calculator(object): # define a calculator object
    def add(self, x, y): # define addition function
        number_types = (int, long, float, complex) # accepted number types

        if isinstance(x, number_types) and isinstance(y, number_types): # if both values are accepted number types
            return x + y # return the sum of the values
        else:
            raise ValueError # if one or both values are not accepted number types return a Value Error

    def subtract(self, x, y):
        number_types = (int, long, float, complex)

        if isinstance(x, number_types) and isinstance(y, number_types):
            return x - y
        else:
            raise ValueError

    def multiply(self, x, y):
        number_types = (int, long, float, complex)

        if isinstance(x, number_types) and isinstance(y, number_types):
            return x * y
        else:
            raise ValueError