CrackePop.py

class CracklePop(object):
    def __init__(self, left, right):
        self.left = left # Left index
        self.right = right # Right index

    # Private methods
    
    def valid_bounds(self):
        """
        Checks that the left and right bounds
        are valid. Returns False when the given numbers are not
        "integers" or the bounds are not valid
        """
        left = self.left
        right = self.right

        return (isinstance(left, int) and isinstance(right, int) and
                left >= 0 and left <= right)

    def composed_message(self):
        """
        Returns string that contains a series that stars on left and finish on right.
        When number is divisible by 3, prints Crackle. If it's divisible by 5 Pop. And CracklePop if both cases.
        """
        output_msg = ""
        for index in range(self.left, self.right + 1):
            if index % 3 != 0 and index % 5 != 0:
                output_msg += str(index)  # only prints number
            else:
                if index % 3 == 0:
                    output_msg += "Crackle"
                if index % 5 == 0:
                    output_msg += "Pop"
            output_msg += "\n"
        return output_msg

    # Public methods
    def get_crackepop_msg(self):
        """
        When bounds are valid, returns the string with the correct series.
        If not, returns a failure message.
        """
        if not self.valid_bounds():
            return 'Bad left and right bounds.'

        output_msg = self.composed_message()
        return output_msg


test1 = CracklePop(1, 100)
print test1.get_crackepop_msg()