[Cython] buffer shape incompatible with memoryview shape

[Dag Sverre Seljebotn]

On 06/21/2012 01:36 PM, Stefan Behnel wrote:
> Dag Sverre Seljebotn, 21.06.2012 13:10:
>> On 06/21/2012 10:59 AM, Stefan Behnel wrote:
>>> I find this worth fixing for 0.17:
>>>
>>> http://trac.cython.org/cython_trac/ticket/780
>>
>> I'm not sure about the timeline here.
>>
>> The object<->memoryview semantics haven't even been hammered down yet; does
>> "mview.customattr" trigger an AttributeError, SyntaxError or fall back to
>> some underlying object (constructing it if necesarry).
>>
>> Until that happens, memoryviews are an experimental feature and present for
>> development purposes mostly, so it's not like this is a big bug that would
>> bite end-users. Thinking about those semantics is much more important...
>
> Absolutely.
>
> I ran into this when I gave a Cython+NumPy course and this was the first
> thing that the attendants tried when I asked them to validate that two
> input arrays have the same size before adding them. It's the one obvious
> way to do it, and it fails miserably. I think it should be fixed, and I
> think it should be fixed soon because it feels really low-level and
> complicated, especially to new users.

Can you clarify a bit -- did you give this course using 
np.ndarray[double, ndim=2], or double[:, :]? They're really very 
separate under the hood and the fix is different.

Or, did you actually use object[double, ndim=2] like in the bug report? 
(Did me and Mark get around to propose deprecating this one on the list?)

Dag