[Numpy-discussion] Creating a descr with aligned=1 using the C API

Travis Oliphant oliphant.travis at ieee.org
Sun Apr 30 21:45:05 CDT 2006

Albert Strasheim wrote:
> Hello all
> I was wondering what the best way would be to create the following descr
> using the C API:
You can use the "new" method.

PyArray_Descr *dtype
PyObject *dict;

dtype = PyArrayDescr_Type.ob_type->tp_new(dtype->ob_type, 
Py_BuildValue("Oi", dict, 1));

where the dict is the one you give.

Yes, this could be an easier-to use API.

> descr = dtype({'names' : ['index', 'value'], 'formats' : [intc, 'f8']},
> align=1)
> One could use PyArray_DescrConverter in multiarraymodule.c, but there
> doesn't seem to be a way to specify aligned=1 and one would have to build
> the dict object before being able to pass it on for conversion.
> Unless there's another easy way I'm missing, the API could possibly do with
> a function like PyArray_DescrFromCommaString(const char*, int align) which
> calls _convert_from_commastring. By the way, what is the general format of
> these commastrings?
It's in the NumPy book and it's also documented by numarray...


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