Filenames need to be treated as binary because of bad designs decades ago. Rust handles this correctly imho, by having a separate type for such strings, OsStr.
Rust had the luxury to learn from mistakes of others :)
When python was created the Unicode didn't even exist.
Anyway in python 3, many os functions accept string and bytes, and might behave depending on it. For example os.walk, if you pass path as byte string, will output paths as bytes.
