On Tue, Aug 25, 2020 at 4:41 PM Stefano Borini <stefano.bor...@gmail.com> wrote:
> On Sat, 8 Aug 2020 at 02:34, Stephan Hoyer <sho...@gmail.com> wrote: > > > I'm sorry, I did a poor job of editing this. > > > > To fill in my missing word: From my perspective, the *only* reasonable > way to add keyword arguments to indexing would be in a completely backwards > compatible way with **kwargs. > > Let me clarify that I don't like the kwargs solution to the current > getitem, and the reason is simple. > > The original motivation for PEP-472 was to do axis naming, that is, to > be sure you would be able to clearly indicate (if you so wished) > data[23, 2] explicitly as e.g. data[day=23, detector=2] or > data[detector=2, day=23] > But that assumes that all keyword axes can be mapped to positional axes. This is not the case in xarray, there are axes that are keyword-only. And it precludes other uses-cases that have been mentioned, such as parameters for indexing. So I understand that this was the original motivation, I don't think it is good to restrict to it only this use-case when there are other valid use-cases. > If you have **kwargs, now the first case would send the two values to > the nameless index, the second case to the kwargs, and inside the > getitem you would have to reconcile the two, especially if someone > then writes data[24, 5, day=23, detector=2] > typing of course has the same issue. What this extended syntax is > supposed to be used for is to define specialisation of generics. but > it's difficult to now handle the cases List[Int] vs List[T=Int] vs > List[Int, T=int], which are really telling the same thing the first > two, and something wrong (TypeError multiple arguments) the second. > That is a problem that anyone using **kwargs in functions has to deal with. It is neither a new problem nor a unique one, and there are plenty of ways to deal with it.
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