What's this all about? To start from the beginning, about Python. Although we are focusing here on PyGTK (especially because starting from Gnome 3 inclusive, it won't continue its development, so that means "renew or die"), this is about porting applications done with intermediate libs that work with GObject (gtk, gdk, webkit...) to GObject Introspection. So what's going to be told on this post is also valid for this other API's.
What's GObject Introspection (link and sublinks are recommended readings)? As can be read from the description from the web and the Debian package itself, it is a project for providing machine readable introspection data of the API of C libraries.
Where do we start from? We can start from this website. The reader should keep in mind, if you haven't already noticed, we're going to use Debian GNU / Linux Testing (currently Squeeze) as a base for this post, especially when making references to package and paths used since may be different for other distributions.
What do we need?
To finish, comment that although the project (PyGi) reflects quite recent development activity and is not yet stabilized, PyGTK developers are urged to start porting applications as soon as possible to help find potential problems and make advance/mature the project. For those interested in Linux-distribution packages, here you have a recent commentary on versions for different distros (although the more adventurous can build their own binaries from sources).
Regarding Naufrago! (here at gnomefiles), the little project that has motivated this post, let me say that some migration from PyGTK (and others) to PyGi has been done. But as long as I'm using Debian GNU/Linux Testing distribution packages, I'm stuck with changes present on python-gobject version 2.26 that are not on current testing/unstable/experimental packages. So I'll wait for maintainers to have it ready to proceed for further steps in my code. Keep up the good work!