Python 3 usually handles this correctly, and I'm a little bit confused what's going on in the article, exactly. For UNIX path names (and other OS data like env

Python 3 usually handles this correctly, and I'm a little bit confused what's going on in the article, exactly. For UNIX path names (and other OS data like environment variables), Python uses the "surrogateescape" error handling method, which does exactly what you ask. Any byte sequence can be converted to a string. If it decodes as valid UTF-8, it will do that. If it hits a byte that does not decode as valid UTF-8 (necessarily a byte >= 128), it will map it to code points U+DC80 through U+DCFF. These are in a reserved ranges of code points ("surrogates", which make it possible to represent code points > 0xFFFF in UTF-16), and they can't show up in actual Unicode text (i.e., there is no UTF-8 encoding of them, strictly speaking, and if you applied the UTF-8 encoding algorithm to a code point in the U+D800 to U+DFFF range, you would get bytes that aren't valid UTF-8). On the way out, this is reversed. So you get the results you expect if your filenames are in UTF-8, but since UNIX has no requirement that filenames are indeed UTF-8 (the only constraint is they can't contain NUL or ASCII-forward-slash), the bytes are preserved in a funky-looking format in Python and you get the exact same output on the other end. See https://www.python.org/dev/peps/pep-0383/ https://www.python.org/dev/peps/pep-0383/ for more on what's going on. The tl;dr for users of Python is that if you want to interact with, say, subprocess output as mostly-normal strings (instead of bytes) but you want to be robust to non-UTF-8 bytes, you should do something like subprocess.check_output(["some", "command"], errors="surrogateescape") You don't need to do this for APIs that directly interact with pathnames, because they do it already. You just need to do it for things like subprocess output and file contents that Python doesn't know you want to handle in this way. ... On Windows, however, path names must be valid Unicode and are stored in UTF-16. So the idea of a "ł" that doesn't decode properly shouldn't even happen! Mikołaj's home directory ought to be a very boring (and valid) 004d 0069 006b 006f 0142 0061 006a on disk. Windows doesn't enforce that file paths are valid UTF-16 though (specifically, the surrogate code points are only supposed to show up in a certain way, but nothing enforces that and you can have random surrogates on disk), and hence Rust, which internally represents all strings in UTF-8, has a solution ("WTF-8") that's basically the inverse of surrogateescape - it uses extrapolated-UTF-8-encoding-of-surrogates to handle unpaired surrogates. http://simonsapin.github.io/wtf-8/ http://simonsapin.github.io/wtf-8/ But it seems very odd to me that the directory C:\Users\Mikołaj would actually contain any of those, and if it doesn't, I would expect it to very easily turn into a Python Unicode string. Maybe this is from a Python version before https://www.python.org/dev/peps/pep-0529/ https://www.python.org/dev/peps/pep-0529/ , which is claimed to "fail to round-trip characters outside of the user's active code page"? Maybe this is from a Python version after that change and it's wrong?