[Python-ideas] PEP for issue2292, "Missing *-unpacking generalizations"

[Guido van Rossum]

I am doubtful that syntax would be LR(1), as required.

On Mon, Jul 15, 2013 at 1:23 PM, Oscar Benjamin
<oscar.j.benjamin at gmail.com>wrote:

> On 15 July 2013 21:06, Guido van Rossum <guido at python.org> wrote:
> > On Mon, Jul 15, 2013 at 1:01 PM, Oscar Benjamin
> > <oscar.j.benjamin at gmail.com> wrote:
> >> On 15 July 2013 12:08, Joshua Landau <joshua.landau.ws at gmail.com>
> wrote:
> >>> On 15 July 2013 11:40, Oscar Benjamin <oscar.j.benjamin at gmail.com>
> wrote:
> >>>
> >>> In fact, I'd much like it if there was an iterable "unpacking" method
> >>> for functions, too, so "chain.from_iterable()" could use the same
> >>> interface as "chain" (and str.format with str.format_map, etc.). I
> >>> feel we already have a good deal of redundancy due to this.
> >>
> >> I've also considered this before. I don't know what a good spelling
> >> would be but lets say that it uses *args* so that you have a function
> >> signature like:
> >>
> >>     def chain(*iterables*):
> >>        for iterable in iterables:
> >>             yield from iterable
> >>
> >> And then if the function is called with
> >>
> >>     for line in chain(first_line, *inputfile):
> >>         # do stuff
> >>
> >> then iterables would be bound to a lazy generator that chains
> >> [first_line] and inputfile. Then you could create the unpacking
> >> iterator I wanted by just using chain e.g.:
> >>
> >>     chain(prepend, *iterable, append)
> >
> > But how could you do this without generating different code depending
> > on how the function you are calling is declared? Python's compiler
> > doesn't have access to that information.
>
> Good point. Maybe you'd have to spell it that way at both ends:
>
>     chain(prepend, *iterable*, append)
>
>
> Oscar
>



-- 
--Guido van Rossum (python.org/~guido)
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