Ask HN: Any resources for passive feature discovery in tools/languages?

I was working with Python recently, and I found a solution to a really specific problem using a metaclass. But I almost didn't. I found it scrolling through the codebase of a big open source project for an unrelated reason.

Similar thing with Git reflog or f/t in Vim—I discovered new features while looking for something else.

I wish I could passively learn things I "wouldn't know to ask" about Python (or git, vim, curl, etc.) without having to

a) Know roughly what I'm looking for; find the answer on Stack Overflow or a blog post.

b) Explicitly devote unguided time to learning the most advanced/obscure features of whatever I'm using—even though that is probably a good exercise.

Any ideas/experience/magical tools that do exactly this?