A Tuesday 16 February 2010 20:14:38 Anthony Foglia escrigué: > Francesc Alted wrote: > > A Tuesday 16 February 2010 13:19:29 Jon Olav Vik escrigué: > >> Anthony Foglia <AFoglia <at> princeton.com> writes: > >>>>> Is there a way to get a Description from a numpy dtype? > >>> > >>> http://www.pytables.org/trac/ticket/263 > >> > >> Maybe you don't need to. This recent enhancement allows you to use a > >> dtype as a description: > >> http://www.pytables.org/trac/browser/trunk/tables/file.py?rev=4230 > >> > >> 633 `description` > >> 634 This is an object that describes the table, i.e. how > >> many 635 columns it has, their names, types, shapes, etc. > >> It can be 636 any of the following: > >> > >> 650 A NumPy dtype > >> 651 A completely general structured NumPy dtype is > >> accepted 652 too, and its field structure will be > >> reflected in the 653 new `Table` object. > > > > Good catch! I forgot about this capability. So, I think I can close > > #263 now. > > That's not quite what I was looking for. I wanted to store the > description myself, so I can check pre-existing tables against that > description. > > Our use case is that we have tables holding data for each day. We'll > need to append days to the end. But sometimes we don't know if any days > already exist. Essentially we need to open our data object in "r+" > mode. The user will probably want to pass in a dtype to construct the > table, if need be. I'd like to test the description obtained from that > with the description from any pre-existing tables, and throw an error > otherwise. > > We have a similar object that aggregates array, and for there I use > Atoms. This works fine because I can convert dtypes to Atoms (and Atoms > also have default values). I was thinking of using the same logic for > our aggregated tables, but can't.
I see. Would it help if you can get a dtype from a Description object via `table.description._v_dtype` and compare it to the dtype the user is passing in? -- Francesc Alted ------------------------------------------------------------------------------ SOLARIS 10 is the OS for Data Centers - provides features such as DTrace, Predictive Self Healing and Award Winning ZFS. Get Solaris 10 NOW http://p.sf.net/sfu/solaris-dev2dev _______________________________________________ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users
