[Python-Dev] Allocation of shape and strides fields in Py_buffer (original) (raw)

Nick Coghlan ncoghlan at gmail.com
Tue Dec 9 13:33:53 CET 2008

Antoine Pitrou wrote:

Alexander Belopolsky <alexander.belopolsky 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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