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

[Guido van Rossum]

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.

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