Want to create my own version of Notational Velocity

[Larz60+]

This list is a bit old, but still helpful for comparison. Just note that many of these have been updated since the list was last updated.
https://wiki.python.org/moin/GuiProgramming

I know for one that my favorite is wxpython phoenix which is a complete rewrite of wxpython for python 3+.

Qt5 is a favorite of many, and it is very good. (python link PyQt5)