def _join_words(words, delimiter=",", conjunction="and"):
    """Join words together for nice printout.

    >>> _join_words(["first", "second", "third"])
    'first, second, and third'
    >>> _join_words(["first", "second"])
    'first and second'
    >>> _join_words(["first"])
    'first'
    """
    if len(words) == 1:
        return words[0]
    elif len(words) == 2:
        return ' {0} '.format(conjunction).join(words)
    else:
        return '{0} '.format(delimiter).join(words[0:-1]) + \
            "%s %s %s" % (delimiter, conjunction, words[-1])