Are there any easy to use python components that could be used in a GUI? It would be great to have something like JSyntaxPane for Python. I would like to know of python-only versions ( not interested in jython ) .
If you're using gtk+, there's a binding of gtksourceview for Python in gnome-python-extras. It seems to work well in my experience. The downside: the documentation is less than perfect.
There's also a binding of QScintilla for Python if PyQt is your thing.
You can use StyledTextCtrl in wxPython. Check out the official demo for an example (The demo code tab for any demo).
You say "in a GUI app" but don't mention the toolkit.
If you are using PyQt, and need a read-only widget, you can use QWebKit which has a whole HTML widget in it based on WebKit, so it supports pretty much anything, from flash to the ACID2 test.
If you want a read-write widget, Qt's QTextEdit supports syntax highlighting, and I wrote an adapter to let pygments worj with it:
http://lateral.netmanagers.com.ar/weblog/2009/09/21.html#BB831
I am sure something similar can be done with other toolkits, but I don't know how.