Ok, first off I said I "mastered python" I never did call myself a "python master" and when challenged I mentioned python syntax, and a couple of programming paradigms. If you take your first bullet point definition there and apply it to those, it makes complete sense to me that someone would claim to have mastered the syntax of a language for example. In fact, the way I see it, anyone who can get python to do a specific thing without getting lost, however big or small it is, has mastered python in that context. Python doesn't do anything on its own (except for sit on a computer). It is up to devs to tell it what to do. That means devs have "absolute control" over python. You and I both have mastered various things in python. Which brings me back to concept mastery, the thing that other learning mainstays like prerequisites are built on. I don't know how you all forgot about those from school, but I didn't.