I vaguely recall seeing a mailing list thread where `{-}` was proposed. I think it was rejected based on parsing ambiguity, i.e. `{-1}` vs `{-}`. (Or it's possible I might be losing my memory)
Wouldn't it lead to the same problem of a lack of consistency?
dict: {}
list: []
tuple: ()
set: {-}
I originally implemented it that way and had that exact same issue (it's one of the revisions on github). Similarly, {/} would also be a problem.
How about {,} or s{} ?
I didn't think to do {,} which I like. s{} looks weird to me, but I couldn't tell you why.
The s{} alternatve is based on the strange r'' or u'' syntax i've gotten used to.
I think {,} is intuitive because it reminds me of syntax for one-element tuples, e.g. (1,) -- but it may make code harder to read, which is not Pythonic.