My experience personally with python3 (and repeated interactions with about a dozen python programmers, including core contributors) is that python3 does not let you trivially work with streams of bytes, esp if you need to do character set conversions, since a tiny python2 script that I have used for decades for conversion of character streams in terminals has proved to be repeated unportable to python3. The last attempt was much larger, still failed, and they thought they could probably do it, but it would require far more code and was not worth their effort.

I'll probably just use rust for that script if python2 ever gets dropped by my distro. Reminds me of https://gregoryszorc.com/blog/2020/01/13/mercurial%27s-journ...

But why care if it's malformed UTF-8? And specifically, what do you want to happen when you get a malformed UTF-8 string. Keep in mind that UTF-8 is self-synchronizing so even if you encode strings into a larger text-based format without verifying them it will still be possible to decode the document. As a user I normally want my programs to pass on the string without mangling it further. Some tool throwing fatal errors because some string I don't actually care about contains an invalid UTF-8 byte sequence is the last thing I want. With strings being an arbitrary bag of bytes many programs can support arbitrary encodings or at least arbitrary ASCII-supersets without any additional effort.

C strings are not bags of bytes because they can't contain 0x00.