[Python-Dev] Re: Should set objects maintain insertion order too?

[Nick Coghlan <ncoghlan@gmail.com>]

Starting with "collections.OrderedSet" seems like a reasonable idea, though - that way "like a built-in set, but insertion order preserving" will have an obvious and readily available answer, and it should also make performance comparisons easier.

Ya, I suggested starting with collections.OrderedSet earlier, but gave up on it. The problem is that the "use case" here isn't really a matter of functionality, but of consistency: "it would be nice if", like dicts enjoy now, the iteration order of sets was defined in an implementation-independent way. That itch isn't scratched unless the builtin set type defines it.