[Python-Dev] Allocation of shape and strides fields in Py_buffer

[Nick Coghlan]

Antoine Pitrou wrote:
> Alexander Belopolsky <alexander.belopolsky <at> gmail.com> writes:
>> I did not follow numpy development for the last year or more, so I
>> won't qualify as "the numpy folks," but my understanding is that numpy
>> does exactly what Nick recommended: the viewed object owns shape and
>> strides just as it owns the data.  The viewing object increases the
>> reference count of the viewed object and thus assures that data, shape
>> and strides don't go away prematurely.
> 
> That doesn't work if e.g. you take a slice of a memoryview object, since the
> shape changes in the process.
> See http://bugs.python.org/issue4580

I have zero problem whatsoever if slice assignment TO a memoryview
object is permitted only if the shape stays the same (i.e. I think that
issue should be closed as "not a bug").

The buffer protocol permits you to edit the DATA held by another object.
It doesn't let you edit the *structure* of that object (which is what
would be implied by changing the shape of the object).

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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