[Python-Dev] future_builtins (was: Backporting PEP 3127 to trunk)

[Collin Winter]

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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