[Python-3000] Set literals (original) (raw)

Guido van Rossum guido at python.org
Mon Aug 28 20:55:30 CEST 2006

On 8/28/06, Georg Brandl <g.brandl at gmx.net> wrote:

Guido van Rossum wrote: > On 8/28/06, Georg Brandl <g.brandl at gmx.net> wrote: >> At python.org/sf/1547796, there is a preliminary patch for Py3k set literals >> as specified in PEP 3100. > > Very cool! This is now checked in.

Wow, that's fast...

Well it passed all unit tests and the rules for the py3k branch are a bit looser than for the head... :)

> Georg, can you do something about repr() of an empty set? This > currently produces "{}" while it should produce "set()".

Right, forgot about that case. I'll correct that now. (Grr, I even mindlessly changed the unittest that would have caught it)

Checkin?

In the meantime, I played around with the peepholer and tried to copy the "for x in tupleorlist" optimization for sets. Results are in SF patch #1548082.

>> Set comprehensions are not implemented. > > ETA? There are some points I'd like to have clarified first: * would it be wise to have some general listcomp <-> genexp cleanup first? This starts with the grammar, which currently is slightly different (see Grammar:79), and it looks like there's quite a lot of (almost) duplicated code in ast.c and compile.c too.

I expec this cleanup to be quite a bit of work since the semantics are seriously different. ([...] uses the surrounding scope for the loop control variables.)

However you might be able to just cleanup the grammar so they are identical, that would be simpler I suspect.

* list comprehensions are special-cased because of the LISTAPPEND opcode. If there isn't going to be a special-cased SETADD, it's probably the easiest thing to transform {x for x in a} into set(x for x in a) in the AST step, with "set" of course always being the builtin set.

Right. That might actually become a prototype for how to the list translation as well.

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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