Re: [Pytables-users] Slicing with index arrays

[Francesc A. <fa...@ca...>]

El dl 18 de 07 del 2005 a les 08:07 -0400, en/na travlr va escriure:
> Actually I'm aware of the "under the hood indexing", but frankly I
> don't use it because it shows nice improvement for some search result
> sizes, and is quite latent on others.

Yes, that's perfectly possible. This kind of indexing use is mainly
aimed for large tables while with small ones (< 10**6 entries) your
mileage may vary.

> What I'm referring to though, with slice indexing, is being able to
> use an array for the index, as numarray does.
> file.table.cols.blah[array] where the array can be non-sequential, as
> is produced by array=numarray.where(x>y)[0].

Ooops, I see. Well, this is in fact already implemented through the use
of Table.readCoordinates() method:

file.table.readCoordinates(array, field="blah")

However, your suggestion is quite good, and implementing it is a matter
of adding a new case in the Column.__getitem__() special method.
Something like:

        [...]
        elif isinstance(key, numarray):
            return self.table.readCoordinates(key, self.name)

would be enough.

> This type of behavior if possible would be less cumbersome than
> iterating, and less memory intensive when brought in and bounded to an
> actual numarray Type in order to facilitate this behavior.

Definitely. I'll try to add such a feature for next release.

Cheers,

Francesc