[Python-Dev] future_builtins (was: Backporting PEP 3127 to trunk)
collinw at gmail.com
Sun Feb 24 23:30:46 CET 2008
On Sat, Feb 23, 2008 at 8:06 AM, Guido van Rossum <guido at python.org> wrote:
> I don't think a -3 warning for oct or hex would do any good.
> I do think map() and filter() should issue a warning under -3 when the
> first arg is None. (Or does 2to3 detect this now?)
2to3 does detect that: it will turn map(None, foo) into list(foo).
> On Sat, Feb 23, 2008 at 6:06 AM, Eric Smith
> <eric+python-dev at trueblade.com> wrote:
> > Georg Brandl wrote:
> > > Eric Smith schrieb:
> > >> Guido van Rossum wrote:
> > >>> I wonder if, in order to change the behavior of various built-in
> > >>> functions, it wouldn't be easier to be able to write
> > >>>
> > >>> from future_builtins import oct, hex # and who knows what else
> > >> This makes sense to me, especially if we have a 2to3 fixer which removes
> > >> this line. I'll work on implementing future_builtins.
> > >
> > > Will the future map and filter also belong there (and if they are imported
> > > from future_builtins, 2to3 won't put a list() around them)?
> > I can certainly do the mechanics of adding the new versions of map and
> > filter to future_builtins, if it's seen as desirable.
> > Maybe we could have 2to3 not put list() around map and filter, if
> > there's been an import of future_builtins. I realize that there are
> > pathological cases where 2to3 doesn't know that a usage of map or filter
> > would really be the generator version from future_builtins, as opposed
> > to the actual list-producing builtins. But would it be good enough to
> > take an import of future_builtins as a hint that the author was aware
> > that 2to3 wasn't going to change map and filter?
> > Still an open issue in my mind is adding a -3 warning to oct and hex,
> > and now conceivably map and filter. Would that be going too far?
> > Eric.
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> --Guido van Rossum (home page: http://www.python.org/~guido/)
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