dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Wed, Feb 24, 2010 at 06:12:29PM -0800, Johan Hake wrote:
> On Tuesday 23 February 2010 11:48:05 Anders Logg wrote:
> > I thought that Array should be automagically mapped to Numpy arrays in
> > Python. This doesn't happen for the new component() function I just
> > added to FunctionSpace.
> >
> > Test by
> >
> >   mesh = UnitSquare(4, 4)
> >   V = VectorFunctionSpace(mesh, "CG", 1)
> >   print V.sub(0).component()
>
> No they are not.
>
> I think we landed on doing this on case to case. You can just call
> V.sub(0).component().array().
>
> The blueprint on the array typemap is not closed. There still exist some
> questions we need to sort out, including (I think) this one.
>
> I cannot come up with a good example just now why we shouldn't just wrap all
> out Arrays to numpy arrays, but I think it had something to do with ownership
> and possibilities of returning an array that potentially might be resized.

Could you try wrapping all Arrays by default?

It would be useful at least for

  FunctionSpace::component()
  TimeSeries::vector_times()
  TimeSeries::mesh_times()

All of these return an Array. It would be natural for these to return
a Python list (or tuple) in Python.

The first one returns a const reference. If it helps I can change it
so it returns by value.

The other two return an Array by value.

Perhaps the natural thing would be for return-by-value Arrays to map
to Python tuples?

--
Anders

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