[Numpy-discussion] Proposal to accept NEP-18, array_function protocol (original) (raw)

Nathaniel Smith njs at pobox.com
Fri Aug 24 18:13:56 EDT 2018

On Fri, Aug 24, 2018 at 1:46 PM, Stephan Hoyer <shoyer at gmail.com> wrote:

On Fri, Aug 24, 2018 at 1:36 AM Hameer Abbasi <einstein.edison at gmail.com> wrote:

On Fri, Aug 24, 2018 at 9:38 AM Nathaniel Smith <njs at pobox.com> wrote: On Thu, Aug 23, 2018 at 9:02 AM, <einstein.edison at gmail.com> wrote: > I might add that most duck array authors are highly unlikely to be > newcomers > to the Python space. We should just put a big warning there while > enabling > and that’ll be enough to scare away most devs from doing it by default. That's a reasonable idea... a Big Obnoxious Warning(tm) when it's enabled, or on first use, would achieve a lot of the same purpose. E.g. if thisisthefirstarrayfunctionusage(): sys.stderr.write( "WARNING: this program uses NumPy's experimental 'arrayfunction' feature.\n" "It may change or be removed without warning, which might break this program.\n" "For details see http://www.numpy.org/neps/nep-0018-array-function-protocol.html\n" ) -n

I was thinking of a FutureWarning... That's essentially what it's for. Writing to stderr looks un-pythonic to me. Issuing a FutureWarning seems roughly appropriate here. The Python 3.7 docs write: "Base category for warnings about deprecated features when those warnings are intended for end users of applications that are written in Python." Writing to sys.stderr directly is generally considered poor practice for a Python libraries. In my experience FutureWarning does a good job of satisfying the goals of being a "Big Obnoxious Warning" while still being silence-able and testable with standard tools.

Yeah, the reason warnings are normally recommended is because normally, you want to make it easy to silence. But this is the rare case where I didn't want to make it easy to silence, so I didn't suggest using a warning :-).

Calling warnings.warn (or the C equivalent) is also very expensive, even if the warning ultimately isn't displayed. I guess we could do our own tracking of whether we've displayed the warning yet, and only even attempt to issue it once, but that partially defeats the purpose of using warnings in the first place.

-n

-- Nathaniel J. Smith -- https://vorpus.org

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