On Wed, 2023-02-08 at 17:08 +0100, Francesc Alted wrote:
> On Wed, Feb 8, 2023 at 3:19 PM Sebastian Berg <
> sebast...@sipsolutions.net>
> wrote:
>
> > On Wed, 2023-02-08 at 14:31 +0100, Francesc Alted wrote:
> > > On Wed, Feb 8, 2023 at 1:42 PM Sebastian Berg <
> > > sebast...@sipsolutions.net>
> > > wrote:
> > >
> > > > On Wed, 2023-02-08 at 12:48 +0100, Francesc Alted wrote:
> > > > > Hi,
> > > > >
> > > > >
> > > >
> > > > <snip>
> > > >
> > > > > Is there a way (or an ongoing effort) to express the variety
> > > > > of
> > > > > data
> > > > > types
> > > > > in NumPy that beats the above (which seems somewhat
> > > > > inconsistent
> > > > > to
> > > > > me)?
> > > >
> > > > How about using the Python buffer interface format string
> > > > (maybe
> > > > with
> > > > some limitations).
> > > >
> > >
> > > If you mean the array interface (
> > > https://numpy.org/doc/stable/reference/arrays.interface.html),
> > > this
> > > is what
> > > dtype.str provides (
> > > https://numpy.org/doc/stable/reference/generated/numpy.dtype.str.html
> > > ).
> > > But the limitation here is that structured types are represented
> > > by
> > > the 'V'
> > > char, which is not properly representing it by any means.
> > >
> >
> > Ah, I was thinking of what the Python buffer protocol uses, which
> > is
> > what struct uses:
> >
> > https://docs.python.org/3/library/struct.html#module-struct
> >
> > That has some annoyances for sure, and structured dtypes with field
> > names need rather strange syntax. Also I think padding bytes at
> > best
> > are simply fields with an empty name.
> > But overall, it probably already does a better job than any `str()`
> > for
> > basic types:
> >
> > In [2]: import numpy as np
> >
> > In [3]: np.array(0, dtype="i,i,2f")
> > Out[3]:
> > array((0, 0, [0., 0.]),
> > dtype=[('f0', '<i4'), ('f1', '<i4'), ('f2', '<f4', (2,))])
> >
> > In [4]: memoryview(np.array(0, dtype="i,i,2f")).format
> > Out[4]: 'T{i:f0:i:f1:(2)f:f2:}'
> >
>
> Aha, that's pretty cool, although I don't think this is flexible
> enough to
> support e.g. field names or nested fields. After pondering about it,
> I
> think we will add a format ID to our spec, and will stick with NumPy
> as the
> default. If in the future another format appears that is more well
> defined, we could still change the representation and use a new ID,
> while
> keeping backwards compatibility if needed.
>
It does support field names. I think the main problem may be that it
cannot support e.g. datetimes. You probably also can't support empty
field names (but maybe that is too weird to be useful anyway).
Not ethat in the output there `T{i:f0}` denotes that it is structured
and the name is "f0". And yes, you can nest another `T{}` inside.
I am not sure whether type codes are limited to single characters
(which IMO wouldn't be nice), which (to me) would seem a bit limited.
I also think we may have to agree on e.g. an empty name denoting
padding.
- Sebastian
> Thanks!
>
>
> >
> > - Sebastian
> >
> >
> > >
> > > > But other than that, I don't have an obvious idea right now.
> > > >
> > > > - Sebsatian
> > > >
> > > > >
> > > > > Thanks!
> > > > > _______________________________________________
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> > > > > Member address: sebast...@sipsolutions.net
> > > >
> > > >
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> >
> >
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