Dead ends in Python!

Since all (builtin) sets in Python are finite, all complements of the builtin sets would be infinite.

Practically, one cannot iterate over an infinite set... so no __iter__ method. Unless maybe we have the complement of the complement of a finite set, but then we'd just have the set.

Also, since len() must return an integer, and a len(SetComplement([])) would be infinity, and you cannot represent infinity as an integer type (well, maybe you can by subclassing int...) but it's not very practical. Anyways, no __len__ method.

This object is interesting theoretically, but has little practical use.