Here is how I interact between Python and QML in FeedingIt. Not sure it's the best way to do it, but you can see in there how the Controller object is declared with its various slots that can be called from QML in this file:
https://garage.maemo.org/plugins/ggi...dca7f1;hb=HEAD

gpodder is probably be a much better example (but might be more complicated, due to its size).