> But how would you invoke them, other than using operator.add and operator.concat?
The case I was thinking of was just a direct call to `operator.concat`. The motivation here is simply to make `operator.concat` do something non-surprising on numpy arrays (be that `np.concatenate(a, b)`, or simply `raise TypeError`). I doubt numpy would actually advocate using it, but we can at least remove the foot-gun. Eric On Fri, 12 Jun 2020 at 17:18, Guido van Rossum <gu...@python.org> wrote: > But how would you invoke them, other than using operator.add and > operator.concat? A better UI would be to define new methods with more > discoverable names. > > On Fri, Jun 12, 2020 at 7:29 AM Eric Wieser <wieser.eric+nu...@gmail.com> > wrote: > >> Hi all, >> >> In the `operator` module, both `operator.concat` and `operator.add` are >> described as performing `a + b`. >> When defining a type in pure python, it is not possible to give these >> different meanings. >> However, when defining a C extension type, it is possible to fill both >> `tp_as_number->nb_add` and `tp_as_sequence->sq_concat` with different >> implementations to obtain different behaviors. >> >> Is the fact that `operator.concat` (`PySequence_Concat`) and >> `operator.add` (`PyNumber_Add`) can have different behaviors an >> implementation detail of CPython, or is it intended behavior in the >> language itself? >> >> I ask because [a recent PR for numpy][1] proposes implementing both of >> these slots, and discussion turned to whether it was intended to be >> possible to do this in the first place, and if so whether a patch will be >> needed to PyPy. >> >> It seems that there was at least some vague intent for this to be >> possible - In bpo-29139, Serhiy said >> >> > Third-party classes (maybe NumPy arrays, I don't know) can have >> different implementations of `sq_concat` and `nb_add`. >> >> It seems to me there are at least three stances that could be taken here: >> >> * Specifying both is considered invalid: python should consider emitting >> a warning in `Type_READY` if both are filled. >> * Specifying both is considered an implementation detail specific to >> CPython: the [C API docs for the type slots][2] should indicate this >> * Specifying both is explicitly allowed and considered a language >> feature. `__concat__` should be added as a slot_wrapper around `sq_concat` >> to allow the language feature to be accessed without writing C extensions. >> >> Eric Wieser >> >> Apologies if this is not the right list - this didn't feel right for >> python-ideas or bpo. >> I'm more than happy to repost this elsewhere if asked. >> >> [1]: https://github.com/numpy/numpy/issues/16489 >> [2]: https://docs.python.org/3/c-api/typeobj.html >> _______________________________________________ >> Python-Dev mailing list -- python-dev@python.org >> To unsubscribe send an email to python-dev-le...@python.org >> https://mail.python.org/mailman3/lists/python-dev.python.org/ >> Message archived at >> https://mail.python.org/archives/list/python-dev@python.org/message/HCXMI7LPWZEKKPRIJTVHN5ZRWIUXM5C3/ >> Code of Conduct: http://python.org/psf/codeofconduct/ >> > > > -- > --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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