[Numpy-discussion] When are 0-d arrays writeable?

Sebastian Berg sebastian@sipsolutions....
Fri Nov 23 08:53:19 CST 2012


On Fri, 2012-11-23 at 10:49 +0000, Nathaniel Smith wrote:
> On 23 Nov 2012 03:34, "Charles R Harris" <charlesr.harris@gmail.com>
> wrote:
> >
> > Examples,
> >
> > In [13]: ones(()).flags.writeable
> > Out[13]: True
> >
> > In [14]: (-ones(())).flags.writeable
> > Out[14]: False
> >
> > In [15]: (-1*ones(())).flags.writeable
> > Out[15]: False
> >
> > In [16]: (1 + ones(())).flags.writeable
> > Out[16]: False
> >
> > In [17]: array(1)
> > Out[17]: array(1)
> >
> > In [18]: array(1).shape
> > Out[18]: ()
> >
> > In [19]: array(1).flags.writeable
> > Out[19]: True
> 
> Looks like a bug in the ufunc output value setup code or something?
> 
It might be possible to rethink when (or if) to convert 0-d array to a
scalar. However, at the moment as far as I understand many functions
generally do not return 0-d arrays but scalars. Which makes sense
because mostly we would rather use scalars then 0-d arrays as they are
closer to typical python (hashable and subclasses of python types).

Of course the way this is done is not aware of what is put in (scalar
vs. 0-d array), since all input is converted to an array normally, which
means that most (all?) functions either return 0-d arrays or scalars and
are never aware if the original input was a scalar or an array. Maybe
there could be a np.asarray_or_scalar or such so that its easier to give
the same output type as the original input type?

Regards,

Sebastian

> -n
> 
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