To start writing in Python, open Mu, click the Mode button to switch to Python 3 mode, then click the REPL button to open the REPL panel.
This is Python’s “Interactive mode.” You can type single commands and see their result. For example, type 2 * 3
and press Enter.
If you already know the basic concepts of programming, you should try the official Python tutorial. If you haven’t programmed before, there is a list of tutorials for beginners here.
Remember to also practice the things you are learning outside of the lessons and tutorials! Make something interesting in Python (not necessarily for robotics) and post it on GitHub. If you have questions you can ask them in the #programming
Slack channel.