The Python lexer works if you set the `lexer.python.unicode.identifiers=1` lexer property. For example a `def Ü():` highlights `Ü` properly.
But the symbol parser or symbol handling doesn't and spews `Warning: : ignoring null tag in /tmp/untitled.py(line: 29)` errors from `ctags/main/entry.c` so I guess the symbol parser system doesn't support it yet. As @codebrainz said, you can open issues on the universal ctags project that supplys the parsers (and a pull request to update Geany :)