No, I am saying it is important to distinguish between "d[3, 4]" and "d[day=3, detector=4]". In xarray there can be label-only dimensions, that is dimensions with no corresponding position. So having all labelled dimensions necessarily mapped onto positional dimensions wouldn't work.
On Sat, Aug 15, 2020, 23:26 Guido van Rossum <gu...@python.org> wrote: > On Sat, Aug 15, 2020 at 8:02 PM Todd <toddr...@gmail.com> wrote: > >> On Sat, Aug 15, 2020 at 7:26 PM Stefano Borini <stefano.bor...@gmail.com> >> wrote: >> >>> > QUESTION >>> > Suppose we have >>> > >>> d[x=1, y=2] = 42 >>> > >>> d[x=1, y=2] >>> > 42 >>> > where d is an instance of a suitable class X that has no special >>> knowledge of keywords. >>> >>> Initially, when I wrote the pep, the idea was that there was no >>> distinction of kwargs and normal args. Basically the idea was that >>> currently the only "metainfo" associated to every argument is purely >>> positional (e.g. the meaning of position 1 is implicit). But index 1 >>> can have a specific semantic meaning (e.g. it could be a day). >>> So in practice they would be one and the same, just that you add >>> non-positional semantic meaning to indexes, and you can refer to them >>> either through the position, or this additional semantic meaning. >>> >>> In other words, if you claim that the first index is day, and the >>> second index is detector, somehow, there is no difference between >>> these >>> >>> d[3, 4] >>> d[day=3, detector=4] >>> d[detector=4, day=3] >>> >>> In fact, my initial feeling would be that you can use either one or >>> the other. You should not be able to mix and match. >>> >>> the pep went through various revisions, and we came to a possible >>> proposal, but it's not set in stone. >>> >> >> This would definitely not be sufficient for xarray, which I see as being >> one of the main users of this syntax. The whole point is to be able to >> specify an arbitrary subset labeled dimensions. >> > > Are you saying that for xarray it is important to distinguish between > `d[day=3, detector=4]` and `d[detector=4, day=3]`? If we just passed the > keyword args to `__getitem__` as an extra `**kwds` argument (which > preserves order, since Python 3.6 at least), that should work, right? If > not, can you clarify? > > -- > --Guido van Rossum (python.org/~guido) > *Pronouns: he/him **(why is my pronoun here?)* > <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/> >
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