[Numpy-discussion] Removing undocumented __buffer__ attribute lookup

[Charles R Harris]

On Wed, Feb 27, 2019 at 1:37 AM Hameer Abbasi <einstein.edison at gmail.com>
wrote:

> Cc-ing in Travis, because he was the original author of the buffer
> protocol, and this is most definitely related.
>
> Best Regards,
> Hameer Abbasi
>
> On Wednesday, Feb 27, 2019 at 9:20 AM, Matti Picus <matti.picus at gmail.com>
> wrote:
> In digging around the code, I found a gem in PyArray_FromBuffer (exposed
> to python as numpy.frombuffer). If a PyObject* does not have a
> tp_as_buffer->bf_getbuffer function, we check if the python object has a
> __buffer__ attribute. If so we use that as buf in
> PyObject_GetBuffer(buf, ...).
>
>
> This seems to stem back to the original numerics code, where getBuffer
> would look up the attribute and call it as a method. PyArray_FromBuffer
> does not call the attribute as a method, it simply passes it on to
> PyObject_GetBuffer, which will then raise an error saying it cannot
> convert a method. You can try this out by creating a class with a
> __buffer__ method and calling numpy.frombuffer on it.
>
>
> I submitted a pull request to remove the code. Since it is undocumented
> and (as far as I can tell) broken, I do not think we need a deprecation
> cycle.
>
>
I vaguely recall using that many, many years ago for some C code, but don't
see anything using it these days.

Chuck
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