Increasingly, I no longer solidly and fully know Python
There once was a time where I felt that I more or less solidly knew and understood Python. Oh, certainly there were dark corners that I wasn't aware of or that I knew little or nothing about, but as far as the broad language went I felt that I could say that I knew it. Whether or not this was a correct belief, it fed my confidence in both writing and reading Python code. Of course the wheels sort of started to come off this relatively early, but still I had that feeling.
For various reasons, it's clear to me that those days are more and more over. Python is an increasingly complicated language (never mind the standard library) and I have not been keeping up with its growth. With Python 3 I'm basically hopeless; I haven't been attempting to follow it at all, which means that there's whole large areas of new stuff that I have no idea about. But even in Python 2 I've fallen out of touch with new areas of the language and core areas of the standard library. Even when I know they're there, I don't know the detailed insides of how they work in the way that I have a relatively decent knowledge of, say, the iterator protocol.
(One example here is context managers and the "with" statement.)
I'm pretty sure that this has been part of my cooling and increased ambivalence with Python. Python has advanced and I haven't kept up with it; there's a distance there now that I didn't feel before. Python 3 is an especially large case because it feels that lots has changed and learning all about it will be a large amount of work. Part of me wonders if maybe Python (at least Python 3) is now simply too large for me to really know in the way that I used to.
You might ask if actually knowing a language this way is even important. My answer is that it is for me, because knowing a language is part of how I convince myself that I'm not just writing Fortran in it (to borrow the aphorism that you can write Fortran in any language). The less I know a language, the less I'm probably writing reasonably idiomatic code in it and the more I'm writing bad code from some other language. This especially matters for me and Python 3, because if I'm going to write Python 3 code, I want to really write in Python 3; otherwise, what's the point?
(I don't have any answers here, in part because of a circular dependency issue between my enthusiasm for writing stuff in Python and my enthusiasm for coming back up to full speed on Python (2 or 3).)