On Sun, Jul 19, 2020 at 10:25 PM Jonathan Goble <jcgob...@gmail.com> wrote:
> On Sun, Jul 19, 2020 at 9:53 PM Stephan Hoyer <sho...@gmail.com> wrote: > >> On Fri, Jul 17, 2020 at 9:22 PM Ricky Teachey <ri...@teachey.org> wrote: >> >>> >>> # The positional arguments aren't part of the KeyObject >>> >>> d[a, b:c, d, e=5, f=6] == d.__getitem__((a, b:c, d), KeyObject(e=5, >>> f=6)) >>> >>> This raises a question that needs to be answered, then: what would be >>> the utility of mixing together positional and kwd arguments in this way? >>> >>> Even the xarray examples given so far don't seem to make use of this >>> mixture. From my knowledge of pandas I am not sure what the meaning of >>> this would be, either. >>> >> >> One use case that comes up in xarray and pandas is support for indicating >> indexing "modes". For example, when indexing with floating point numbers >> it's convenient to be able to opt-in to approximate indexing, e.g., >> something like: >> array.loc[longitude, latitude, method='nearest', tolerance=0.001] >> > > I had to stare at this for a good 30 seconds before I realized that this > wasn't a function/method call. Except for the square brackets instead of > parentheses, it would be. > > Honestly, this whole idea smells to me like just wanting another type of > function call with different semantics. > > IMHO the above example would be better spelled as: > > array.loc.get(longitude, latitude, method='nearest', tolerance=0.001) > > Pros: Much more obvious, perfectly legal today, zero backward > compatibility issues, probably the way many libraries with such > functionality are doing it now. > Cons: A few extra characters (depending on the method name; here it's only > four) and a couple of taps on the Shift key (but you're already used to > that). > > Whereas for the indexing example: > > Pros: Explicit about indexing a collection and returning an item (but a > good method name like "get" also has this quality). > Cons: Not immediately obvious to an uninitiated reader of the code, new > syntax, code using it is not compatible with Python 3.9 or earlier. > > As for setting a value, the indexing approach has a bit more value (since > a function call can't be an lvalue), but you can just change the method > name from "get" to "set" and add an extra parameter to be the value to set, > and you're done. The pros and cons still apply. > > TL;DR: -1 all the way. Just use ordinary methods. > Another Con for the function call approach, you don't get to use the nice slicing syntax. Compare: >>> array.loc.get(slice(None), slice(None), method='nearest', tolerance=0.001) >>> array.loc.get[:, :, method='nearest', tolerance=0.001] You also can't delete using a function call: >>> del array.loc.get[:, :, method='nearest', tolerance=0.001]
_______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/EVP5ZCBMS3ZYORMCI7LHSFX3CEMZTBKW/ Code of Conduct: http://python.org/psf/codeofconduct/
