I believe sciencerobot is saying that "<>" could be used as the empty set literal.

Oh I see, thanks. "s=<>" is less ugly than "s={@}" but, obviously, is inconsistent with "s={1, 2, 3}".

Then fix that: s = <1,2,3>

I think that's better than using the same brace-type for sets and dicts anyway, and it can't be as confusing as () == tuple(), (x) == x, (x,) == tuple([x]).

Yes, that was the idea. I don't think it would be confusing to the parser.