Bioinformatics graduate who can understand Python code but can’t write it from scratch — how should I actually learn?

[u/Life-Detective-395]

I have a Master’s in Data Science with a previous background in wet-lab biology. My programming experience mainly came through my MSc, so I don’t have a traditional CS background.
At this point, I can usually **understand Python code when I see it**, explain what it is doing, and modify parts of it. But if you give me a problem and ask me to write the solution from scratch, I struggle — and I often rely on ChatGPT to get started.
I’m trying to figure out what the right way to overcome this is.
Should I:
go back and systematically learn Python/CS fundamentals through tutorials first, then start projects?
or keep building bioinformatics projects and use ChatGPT as a tutor/coding assistant while gradually becoming more independent?
I find learning programming purely through tutorials quite difficult and passive, especially because I’ve never studied CS formally.
**For people who came into bioinformatics from biology rather than CS: how did you actually learn to code independently? What should I be able to do before I consider myself “good enough” at Python for a junior bioinformatics role?**

[u/jaiagreen]

If you can understand code, build on that rather than starting from the bottom. Take some old code and delete a few lines here and there. After giving yourself time to forget, can you fill in those lines? (You can also ask AI to make examples like this for you.) Once you're pretty good at that, delete bigger chunks of code. Then just start with an outline. Tada, now you can write from scratch.