def _join_list(lst, oxford=True):
    """Join a list of words in a gramatically correct way."""
    if len(lst) > 2:
        s = ', '.join(lst[:-1])
        if oxford:
            s += ','
        s += ' and ' + lst[-1]
    elif len(lst) == 2:
        s = lst[0] + ' and ' + lst[1]
    elif len(lst) == 1:
        s = lst[0]
    else:
        s = ''
    return s