Hi all, I think the addition of a universal set object would be a nice touch for python sets. Manipulation of collections of sets becomes much easier with it. Right now, certain operations are easy because empty sets are easy to create while the dual operation requires special cases: set_union = set() for s in sets: set_union |= s # this doesn't work set_intersection = set(???) for s in sets: set_intersection &= s Instead you have to do something contorted like: if len(sets) == 0: set_intersection = set() else: sets_i = iter(sets) set_intersection = sets_i.next() for s in sets: set_intersection &= s Implementation of a universal set would be pretty trivial. Trails of EasyExtend [1] has an implementation (albeit used a bit differently) that's basically the entirety of what's needed. The above intersection case would end up looking something like: set_intersection = set.universal() for s in sets: set_intersection &= s Thoughts? I'm happy to write the patch myself if people like this idea. Thanks, Andy Kish. [1] http://fiber-space.de/wordpress/?p=322