What I like about "cramming a ton of functionality into [a single expression]" is that it doesn't leak any intermediates to the rest of the block, and it doesn't allow for mutation. There's a single output exposed; you can't accidentally use the wrong value downstream. You could wrap it all in an inner function, I guess, but that seems like overkill unless you plan to reuse it.

Though to be fair, having explicit intermediate variables is idiomatic in Python, from what I've seen. It's one of my biggest pet-peeves about the language, but it's not without precedent.