Konrad Hinsen writes:
> 
>  Pearu Peterson <pearu@[...].ee> writes:
> 
>  > I think it would be confusing if the result of repr would be `2' and not
>  > `array(2)' because 2 and array(2) are not equivalent in all usages
>  > but it should be clear from repr results as a first way to learn more
>  > about the objects.
> 
>  I agree. There will already be some inevitable confusion with both
>  rank-0 arrays and scalars around, with similar but not identical
>  behaviour. Rank-0 arrays shouldn't make it worse by using camouflage.
> 
I also agree that having repr hide the fact that it is an array is
a bad thing. But do you find getting "array(2)" when indexing
a single item acceptable when working interactively? I agree that
displayhook is probably the best way of altering this behavior if
a user desires (perhaps we will provide a module function to do so, but
not enable it by default).

>  >
>  > Could array.__getitem_ and __getslice__ detect if their argument is
>  > an array and skip using Python objects when iterating over indices?
> 
>  Of course they know that they are indexing an array, they are
>  defined at the level of the array class/type. However, they cannot
>  detect an iteration as opposed to a single item access.
> 
I don't know that it is desirable either to have iteration
return different kinds of objects than explicit indexing, even
if possible. Do we really want

for val in x:
    ...

to use scalars while

for i in range(len(x)):
    val = x[i]
    ...

uses rank-0 arrays? I'm inclined not to have different behavior for
what seems like identical iteration.

>  I don't know if this efficiency problem could be important in
>  practice, probably only practice can tell. I have no idea how many
>  single-item indexing operations into arrays occur in my code, this is
>  not something I worried about when writing it.
> 
>  If there will be scalar and rank-0 array returning variants of
>  indexing anyway, then I suppose that changing the index syntax
>  to one or the other is not a big effort. So my suggestion is to
>  make a test release and see what the reactions are.
> 
That is our plan (hence the reference to "experimental"), but I
wanted to see if there were strong feelings on this before doing so.

Perry



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