Python: convert int to mode string

def _convert_mode(mode: int):
    if not 0 <= mode <= 0o777:
        raise RuntimeError
    res = ''

    for v in range(0, 9):
        if mode >> v & 1:
            match v % 3:
                case 0:
                    res = 'x' + res
                case 1:
                    res = 'w' + res
                case 2:
                    res = 'r' + res
        else:
            res = '-' + res
    return res


print(_convert_mode(0o757))

mode_list = dict(zip(range(9), list('rwx') * 3))


def _convert_mode(mode: int):
    if not 0 <= mode <= 0o777:
        raise ValueError

    res = ''
    # 8 -> 0, 7 -> 1  =>  v + x = 8
    for v in range(8, -1, -1):
        if mode >> v & 1:
            res += mode_list[8 - v]
        else:
            res += '-'
    return res


print(_convert_mode(0o577))