[Numpy-discussion] C-API: multidimensional array indexing?

[Johann Bauer]

Dear experts,

is there a C-API function for numpy which implements Python's
multidimensional indexing? Say, I have a 2d-array

PyArrayObject * M;

and an index

int i;

how do I extract the i-th row or column M[i,:] respectively M[:,i]?

I am looking for a function which gives again a PyArrayObject * and
which is a view to M (no copied data; the result should be another
PyArrayObject whose data and strides points to the correct memory
portion of M).

I searched the API documentation, Google and mailing lists for quite a
long time but didn't find anything. Can you help me?

Thanks, Johann
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[Mark Wiebe]

Probably the easiest way is to emulate what Python is doing in M[i,:] and M[:,i]. You can create the : with PySlice_New(NULL, NULL, NULL), and the i with PyInt_FromLong. Then create a tuple with Py_BuildValue and use PyObject_GetItem to do the slicing.

It is possible to do the same thing directly in C, but as you've found there aren't convenient APIs for this yet.

Cheers,

Mark

[Johann Bauer]

Thanks, Mark! Problem solved.