bytes.upper is the Right Thing when you are dealing with ASCII-based formats. It also has the advantage of breaking in less random ways than unicode.upper. And

bytes.upper is the Right Thing when you are dealing with ASCII-based formats. It also has the advantage of breaking in less random ways than unicode.upper. And I mean, I can't really think of any cross-locale requirements fulfilled by unicode.upper (maybe case-insensitive matching, but then you also want to do lots of other filtering).