[Numpy-discussion] Initializing array from buffer

Stefan van der Walt stefan at sun.ac.za
Mon Nov 17 06:03:09 EST 2014

Hi Andrea

On 2014-11-16 19:42:09, Andrea Arteaga <andyspiros at gmail.com> wrote:
> My use case is the following: we have a some 3D arrays in our C++
> framework. The ordering of the elements in these arrays is neither C nor
> Fortran style: it might be IJK (i.e. C style, 3rd dimension contiguous in
> memory), KJI (i.e. Fortran style, first dimension contiguous) or, e.g. IKJ.
> Moreover we put some padding to optimize aligned access. This kind of
> memory structure cannot be just expressed as 'C' or 'Fortran', but it can
> be perfectly expressed using the Python buffer protocol by providing the
> shape and the strides. We would like to export this structure to a numpy
> array that should be able of accessing the same memory locations in a
> consistent way and make some operations like initializing the content or
> plotting it.
> Is this currently possible?
> If not, is it planned to implement such a feature?

This looks like something that should be accomplished fairly easily
using the ``__array_interface__`` dictionary, as described here:


Any object that exposes a suitable dictionary named
``__array_interface__`` may be converted to a NumPy array. It has the
following important keys:

    data: (20495857, True); 2-tuple—pointer to data and boolean to indicate whether memory is read-only
    version: 3


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