On Tue, 2022-02-15 at 10:21 +0200, Matti Picus wrote:
>
> On 15/2/22 09:53, Stefan van der Walt wrote:
> > On Mon, Feb 14, 2022, at 12:45, Sebastian Berg wrote:
> > > But this is currently *not* consistently the case. I wish to
> > > make this
> > > consistent. The confusion is around object arrays, though:
> > >
> > > value = np.array(None, dtype=object)
> > > arr[0] = value
> > >
> > > Stores `value` without unpacking it currently.
> > >
> > > arr.fill(value)
> > >
> > > Stores the `None` (unpacking `value`) if and only if `value` is
> > > 0-D.
> > That last behavior doesn't look right to me. An object array
> > should be thought of as a collection of pointers, and if you happen
> > to want to point to a NumPy array, so be it.
> I think we should strive for consistency and code simplicity. In the
> non-object case, it is clear that assignment will try to unpack an
> ndarray. So we should do the same thing with object arrays, and
> document
> the change in behaviour. Could we suggest a backward compatible
> alternative (would using a record dtype fit better with Stefan's
> mental
> model)?
A possible workaround might be `arr.itemset()`, although I am not quite
convinced that it should do that.
A structured array could behave differently maybe, but presumably:
arr = np.array([1], "i,i") # structured
arr[0] = (np.array(3), np.array(3))
Should also unpack (with correct casting, not via `__int__`).
I guess we may have less special cases if we just unpack 0-D and _try_
to always pack N-D arrays with N>0 (which will often fail).
I have to admit, I don't care too much about that special case. The
point is that if done right these special cases should be confined to
two places:
1. Discovering the dimension/dtype in `np.asarray(nested_objects)`
2. The `PyArray_Pack` that sets a single element of an array from an
arbitrary Python object.
And in the first part, we need special paths for "object" anyway. I
can live with a "special case", if it is confined to `PyArray_Pack`.
There are always weird things, e.g. Quantities does *never* want to be
unpacked right now even though it is a subclass so we already have
"tricky stuff" that really means we should channel all through "one
right way", no matter how that way actually looks like.
Cheers,
Sebastian
>
> Matti
>
>
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