def single_splits(words=None):
    """Generate list of single splits of words excluding empty sequence.

    words can be a sequence of strings or a string to to be split
    into words delimited by whitespace

    single_splits('a b c') returns [('a', 'b c'), ('a b', 'c')]

    """
    if words is None:
        return set()
    elif isinstance(words, str):
        words = words.split()
    return [
        (" ".join(words[:i]), " ".join(words[i:]))
        for i in range(1, len(words))
    ]