Can come in handy. When every new version of Ruby came out I read the whole manual.

Then one day I was examining some source code when I stumbled over the Inject statement, which I'd never heard of.

Sure enough - new version had taken me by surprise.

No.

It's probably nigh impossible to "memorize" every single one. I would advise against skipping the "boring" tutorials because even if you don't need to memorize anything, having exposure to, and getting an innate sense of at least what's possible is very much advantageous. You may not think you'll need them now, but I guarantee at some point you'll be trying to achieve something and think, "dang, I wish I could just do X with Y" and then you'll think, "wait, I remember something in a tutorial I saw that did something like that." That will then put you on the path to tracking down whatever it is, usually in the docs.

Also, always keep a tab open to the Python (or whatever language) docs. Can't stress that enough.

100% no. It's kind of like learning a spoken language — English has thousands of words, but only a few hundred are spoken in normal conversation. What will end up happening is you'll start to remember the ones you use most commonly, and if you ever run into a situation where you need to do something but don't know how, you'll end up searching the web for how to do it. In most cases there won't be a single function that does that thing, but often there will be some function that makes doing it easier. You'll use it, and probably forget it right after, but if you encounter it enough you'll start to remember it. Also, going to the language's API doc and searching (ctrl-f in the browser) is really helpful as a starting point before you go on to stackoverflow and such.

There's very little out there worth memorizing. It does however help to be aware of what's available. When you find yourself in a situation where it'd be useful, you'll know where to look.