pretty sure the point is that it's supposed to be in one line

It's supposed to be a single expression. You can write multiple lines by encasing the expression with parentheses.

Thanks, not sure if if it's doable without walrus operator, which I've not had the occasion for previously.

Possible w/out walrus

(but —due to walrus' rather expansive notions of scope— the sol'ns using it are shorter)