Like you, I know the O(n^2) bahaviour that would occur with a naive repeated concatenation, and like you I would know how to deal with it. You'd use "".join(...

Like you, I know the O(n^2) bahaviour that would occur with a naive repeated concatenation, and like you I would know how to deal with it. You'd use "".join(...) for the special case it was strings and therefore so would I. This needn't be a footgun of any sort, and don't assume I (or others) are ignorant.