Ah! Thanks for the correction. Somewhere along the way I picked up the belief that in addition to the file-closing aspect, "with" ensured a line-at-a-time itera

Ah! Thanks for the correction. Somewhere along the way I picked up the belief that in addition to the file-closing aspect, "with" ensured a line-at-a-time iterator, akin to adding on "for line in f:". I'm not sure I understand your third comment though. As I understand it, iterables have an __iter__ method. __iter__ methods return iterators. So an iterator for the iterable f traverses f and sends f's values to, in this case, set(). I believe we agree there. My initial concern was simply that the statement could be read "The iterator, set(), uses f.", and I don't see where the disagreement arises.