def pluralize(number, singular, plural=None):
    """Helper function for getting the appropriate singular or plural
    variant of a word or phrase.

    pluralize(0, 'awoo')         #=> "0 awoos"
    pluralize(1, 'awoo')         #=> "1 awoo"
    pluralize(2, 'awoo')         #=> "2 awoos"
    pluralize(1, 'box', 'boxen') #=> "1 box"
    pluralize(2, 'box', 'boxen') #=> "2 boxen"
    """
    if plural is None:
        plural = singular + 's'

    if number == 1:
        ret = singular
    else:
        ret = plural

    return '{} {}'.format(number, ret)