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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