One thing I want to point out is that when I first read "do one thing", I thought I knew what they were saying and I didn't. It took a long time for me to final

One thing I want to point out is that when I first read "do one thing", I thought I knew what they were saying and I didn't. It took a long time for me to finally grasp that message. One of the ways I finally learned that was after learning async/await in C#. Every beginner to async methods dread in fear once they realize the "zombification" of the Task<T> return type, where if you call an async function 6 layers deep into your program you need to change the return type all the way up the stack. Almost always now I call the async function at the very top layer. If I need some value or list I compute that list or value and return that all the way up then make the async call at the top based on it. I learned to split my functions into two types, pure functions and impure functions. Async functions are an example of an impure function. The only thing those functions are allowed to do is their impure thing. Make a web call, push a value into a database, whatever. The pure functions are where you actually do your computations and transformations. If you have a pure function that has a bug and you need to change it, because it's a pure function it is inherently testable. Just run it and see. If you're not sure, it's trivial to create a new function with the bugfix and only call that function from the places that you are sure of. But then try to make sure.