Most compatible AND useful toolkit for use in GNOME

[Marco Scannadinari <marco scannadinari co uk>]

Hi,
What are your recommendations for a toolkit that is best suited to GNOME
app development (obviously GTK+3), but also useful in developing apps
for other distros / OSs - I feel that the general suggestion is Qt.
Others have said even wxWidgets, because it draws native widgets
according to the environment.
Keep in mind my language of choice is python (3) and am quite new to
graphical app development.

Thanks,
-- 
Marco Scannadinari <marco scannadinari co uk>