Re: [Pytables-users] iterate over specific Tables

[Anthony S. <sc...@gm...>]

Hi Uwe,

Sorry, I wrote this when I was away from my computer and so I couldn't test
it.
Our documentation is clearly wrong then.    However, what you *can* do is
take
the dtype from a known VideoNode table and then compare using this.

known_dtype = f.root.path_to_a_video_node.dtype
bar = filter(x.dtype == known_dtype for x in f.walkNodes('/', 'Table'))

Note that in your file your file you could create an empty table with the
VideoNode
description at a specific location just so that you can read out this dtype.

Be Well
Anthony

On Mon, May 21, 2012 at 6:20 AM, Uwe Mayer <uwe...@df...> wrote:

> Hi Anthony,
>
> On 05/19/2012 08:12 PM, Anthony Scopatz wrote:
> > Hello Uwe,
> >
> > Why don't you try something like:
> >
> > bar = filter(x.description == VideoNode for x in f.walkNodes('/',
> 'Table'))
> >
> > or
> >
> > bar = filter(x.dtype == VideoNode._v_dtype for x in f.walkNodes('/',
> > 'Table'))
> >
> > to compare the dtype / description directly?
>
> correction on my behalf, that would be exactly what I needed, but:
>
> - x.description compares false to a (correct) subclass of
> tables.IsDescription
>
> - a subclass of tables.IsDescription has no property _v_dtype to compare
> to x.dtype (from your example above)
>
>
> Any other ideas?
>
> Thanks in advance,
> Uwe
>
>
> > On May 18, 2012 8:00 AM, "Uwe Mayer" <uwe...@df...
> > <mailto:uwe...@df...>> wrote:
> >
> >     Hi,
> >
> >     I have several leaf nodes of the same table dtype:
> >
> >     class VideoNode(tables.IsDescription):
> >         ...
> >
> >     Not all tables in the hdf5 file are of the same type, however. How
> >     do I iterate
> >     over all leafes which are tables of the above class, while ignoring
> >     tables with
> >     different signatures?
> >
> >     i.e. I'd like to write something like:
> >     <code>
> >     f = tables.openFile(...)
> >     foo = f.walkNodes('/', classname='VideoNode')
> >     </code>
> >     which does not work because only the class name is "Table"...
> >
> >     or
> >     <code>
> >     bar = filter(isinstance(x, VideoNode) for x in f.walkNodes('/',
> >     'Table')))
> >     </code>
> >
> >     which does not work, because x is never an instance of VideoNode.
> >
> >     Any ideas?
> >
> >     Thanks in advance
> >     Uwe
> >
> >
> >
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