[Numpy-discussion] Request for a bit more info on structured arrays in the "basics" page

Ralf Gommers ralf.gommers@googlemail....
Sat Mar 5 08:28:02 CST 2011


On Sat, Mar 5, 2011 at 8:09 AM, Russell E. Owen <rowen@uw.edu> wrote:
> The page <http://docs.scipy.org/doc/numpy/user/basics.rec.html>
>
> gives a good introduction to structured arrays. However, it says nothing
> about how to set a particular element (all fields at once) from a
> collection of data.
>
> For instance:
>
> stArr = numpy.zeros([4,5], dtype=[("pos", float, (2,)), ("rot", float)])
>
> The question is how to set stArr[0]?
>
> >From experimentation it appears that you can provide a tuple, but not a
> list. Hence the following works just fine (and that the tuple can
> contain a list):
> strArr[0,0] = ([1.0, 1.1], 2.0)
>
> but the following fails:
> strArr[0,0] = [[1.0, 1.1], 2.0]
> with an error:
> TypeError: expected a readable buffer object
>
> This is useful information if one is trying to initialize a structured
> array from a collection of data, such as that returned from a database
> query.
>
I'm wondering if that's not a bug? If it's intentional then it is
certainly counterintuitive.

Ralf


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