oswalk.py

def oswalk(dirname):
    if not os.path.isdir(dirname):
        return

    names = os.listdir(dirname)
    filenames = []
    dirnames = []

    dirpaths = []

    for name in names:
        path = os.path.join(dirname, name)
        if os.path.isdir(path):
            dirnames.append(name)
            dirpaths.append(path)
        else:
            filenames.append(name)

    yield (dirname, dirnames, filenames)

    for path in dirpaths:
        yield from  oswalk(path)