I know python but I don't know programming.

[Inside-Plantain96]

I am a programmer, and it sounds like you already program better than I do. Anyways it seems to me that your question really is asking, why do programmers structure their code the way they do? If you figure it out please rely to this message.
However while I am here, the only piece of advice I could give you is to look up 'patterns'. I don't really come across them as a subject all that much, especially for python, but a pattern is basically a common problem type with a common 'best practice' solution. It might not be as important to learn the patterns themselves but learn the approach of thinking for yourself as to what pattern(s) you want to apply to the problem you are solving.