I stepped into python gui programming and I wanted to know what the best documented GUI builder like GLADE, which I'm using right now, however I struggle so much to find some good tutorials or documentation, mostly in the even handling area.
I would like also to understand what's the best/documented GUI framework.
Thanks to anyone who will answer.
There is no "best/documented GUI framework". There are many GUI toolkits, all more-or-less equally powerful. Tkinter, PyQT, wxPython... all have their strengths and weaknesses. Pick any one of them and start learning. 
I recommend Tkinter for learning, mainly because you probably already have it. Once you understand the fundamentals of event based programming (and Tkinter provides a fairly gentle way to learn that), you'll be in a better position to judge which of the available toolkits fits your definition of "best".
what the best documented python friendly GUI builder like GLADE