Hey there!
I'm a chemical physicist who has been using python (as well as matlab and R) for a lot of different tasks over the last ~10 years, mostly for data analysis but also to automate certain tasks. I am almost completely self-taught, and though I have gotten help and tips from professors throughout the completion of my degrees, I have never really been educated in best practices when it comes to coding.
I have some friends who work as developers but have a similar academic background as I do, and through them I have become painfully aware of how bad my code is. When I write code, it simply needs to do the thing, conventions be damned. I do try to read up on the "right" way to do things, but the holes in my knowledge become pretty apparent pretty quickly.
For example, I have never written a class and I wouldn't know why or where to start (something to do with the init method, right?). I mostly just write functions and scripts that perform the tasks that I need, plus some work with jupyter notebooks from time to time. I only recently got started with git and uploading my projects to github, just as a way to try to teach myself the workflow.
So, I would like to learn to be better. Can anyone recommend good resources for learning programming, but perhaps that are aimed at people who already know a language? It'd be nice to find a guide that assumes you already know more than a beginner. Any help would be appreciated.
While there are lots of programming courses out there, not many of them will explicitly teach you about good programming principles. Here are a couple things off the top of my head:
High cohesion, low coupling. That is, when you divide up code into functions and classes, try to minimize the number of things going between those functions (if your functions regularly have 6+ arguments, that's a red flag and should be reviewed). And when something needs to be broken up into pieces, try to find the spots where there are minimal points of contact.
Try to divide code between functions and files in a way that doesn't feel too busy. If there are a bunch of related functions that are cluttering up one file, or that are referenced from multiple places, consider making a module for those. If you're not sure what "too busy" means...
Read a style guide. There are lots of things that will help you clean up and organize your code. The guide won't necessarily tell you why to do each thing, but it's a great tool when you don't have another point of reference.
If you have a chance to take a "Software Engineering 101" class, this is where you'd learn most of the basic principles for writing better code.