[Numpy-discussion] record array with array elements

Igor Sylvester igorsyl@gmail....
Tue Jan 6 22:04:49 CST 2009


If array fields should be of the form (name,subdtype, shape), how do I
specify field offsets? My datatype is word-aligned.

Thanks.

On Tue, Jan 6, 2009 at 3:41 PM, Robert Kern <robert.kern@gmail.com> wrote:

> On Tue, Jan 6, 2009 at 14:07, Igor Sylvester <igorsyl@gmail.com> wrote:
> > Everyone,
> >
> > Shouldn't the itemsize below be 2?
> >
> >>>> import numpy as np
> >>>> dtype = np.dtype( [ (((2,), 'top'), [('nested', 'i1')]) ] )
> >>>> dtype.itemsize
> > 1
> >>>> np.__version__
> > '1.0.4'
> >
> > The elements of the dtype are of type array of size 2.  Each element is a
> > (nested) record array of size 2 with one field of type 'i1'.  In
> contiguous
> > memory, this should look identical to an 'i1' array of size 2.
>
> That's not a valid dtype. Array fields should be of the form (name,
> subdtype, shape), not ((shape, name), subdtype). I'm not sure why
> dtype() does not simply reject this input.
>
> In [22]: np.dtype([('top', [('nested', 'i1')], (2,))]).itemsize
> Out[22]: 2
>
> --
> Robert Kern
>
> "I have come to believe that the whole world is an enigma, a harmless
> enigma that is made terrible by our own mad attempt to interpret it as
> though it had an underlying truth."
>  -- Umberto Eco
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