You are confusing the two different uses of `in`. There's no reason to use a set for a temporary iteration container; but using a set is ideal and - in theory,

You are confusing the two different uses of `in`. There's no reason to use a set for a temporary iteration container; but using a set is ideal and - in theory, for large n or expensive equality check - more performant as a temporary containment container: if x in {1, 2, 3}: print(x)