pyRevit is a great framework to explore customization of Revit. I published a quick start video on YouTube showing how to set up a custom Ribbon and very simple Hello, World script using pyRevit.
Download and install pyRevit.
Create the folders, extension.json file, write the python script, and grab an icon.
Load and enable the extension from pyRevit Settings and Extensions.
Thanks for watching. I hope it helps you keep it In the Pocket.