[Numpy-discussion] Re: Trying out Numeric3

Scott Gilbert xscottg at yahoo.com
Sat Mar 26 13:37:13 CST 2005


--- Stephen Walton <stephen.walton at csun.edu> wrote:
> Scott Gilbert wrote:
> 
> >It's nice because it fits with the rest of the array semantics and
> creates
> >a consistant system:
> >
> >    Array3D = zeros((1, 1, 1))
> >
> >    Array2D = Array3D[0]
> >    Array1D = Array2D[0]
> >    Array0D = Array1D[0]
> >  
> >
> Hmm...in both Numeric3 and numarray, the last line creates a Python 
> scalar.  Array2D and Array1D by contrast are not only arrays, but they 
> are views of Array3D.

I should have been clear that I wasn't describing what any of the array
packages do today.  The views thing is a different can of worms (I think
they should be copy-on-write copies by default and views only when
explicitly asked for).


>  Is what you're saying is that you want Array0D to 
> be a rank-0 array after the above?
> 

Yes.  I think it fits the pattern and is consistant.  There are also cases
where it is useful.

Array operations form a nice little calculus.  Returning non-mutable
scalars in place of rank-0 arrays is like having (2 - 1 == 1) while (2 - 1
- 1 == a donut).  0 looks like a donut, but it's a different food group. 
:-)


>
> >    Array0D[()] = 1
> >
> Of course, this generates an error at present:  "TypeError: object does 
> not support item assignment" since it is a Python int.  Moreover, it 
> isn't a view, so that Array0D doesn't change after the assignment to 
> Array3D.  Is this also slated to be changed/fixed using rank 0 arrays?  
> Would Array0D.shape be () in that case?
> 

Array0D.shape would be an empty tuple () in that case.

I can't say what either Numeric3 or Numarray will do.  The last time I read
the Numeric3 PEP, it looked like there were going to be several special
types of scalars.






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