As a biologist, how do I step up my programming skills?

I would regard my self-taught programming ability with Python at beginner to intermediate (ie, I know how to structure a google search to find helpful Stackoverflow answers), and have middling abilities with R. I did some ML for my PhD work, but it's nothing fancy. My python-fu probably would make a programmer cry.

I've been looking to upgrade my programming skills, and wondering what's the recommended "proper" way for someone with my background to go about it? Is there a MOOC or book that's the go-to?

I've seen suggestions for "How to Design Programs" & SICP, and I've been looking at Racket with interest.