The thing that made it really click with me was the quote (two whom I'm not sure it belongs to) that is roughly "code to abstractions/interfaces, not implementa

The thing that made it really click with me was the quote (two whom I'm not sure it belongs to) that is roughly "code to abstractions/interfaces, not implementation". The idea that I take advantage of good abstractions and I send those objects into my classes that need to perform actions via those abstractions made a lot of sense. Helps enable good polymorphism, as well as unit testing and other things. I don't think I'm doing it justice, but the idea took a good while to understand there reasons behind it. Some books that helped me grok the idea were - Patterns of Enterprise Application Architecture - Clean Architecture - Architecture Patterns with Python along with running into problems that could be easily solved with a decent abstraction at work and learning to apply it directly.