VO Tables

Contents

VO Tables#

Create a VO Table from an Astropy Table#

There are several ways of doing this, and there are a few object layers here, which can be confusing:

Standard astropy Table objects
Votable Table objects
Votable VOTableFile objects (may contain multiple votable Tables)

Although some things can be done with generic astropy Tables, other VO operations can only be done with VO Tables or VOTableFile objects.

This is easiest to see with an example.

import io, numpy

from astropy import table as aptable
from astropy.io import votable as apvot

Create a table with only two columns starting from an astropy Table#

myaptable=aptable.Table(
    numpy.array([
            [19.0186,       46.7304],
            [20.2887,       40.4703],
            [125.886,       21.3377],
            [136.002,       21.9679],
            [141.057,       40.6372],
            [146.700,       22.0116],
            [148.785,       14.2922],
            [149.751,       17.8168],
            [175.039,       15.3270],
            [191.542,       30.7317],
            [194.913,       28.8959],
            [199.026,       41.5011],
            [206.577,       43.8511],
            [209.963,       38.1821],
            [213.556,       15.6214],
            [219.967,       42.7421],
            [226.693,       12.8502],
            [237.489,       20.8057],
            [241.519,       20.8014],
            [317.088,       18.2002],
            [329.235,       6.64845],
            [333.830,       37.3012] ]),
    names=["RA","DEC"])

print(type(myaptable))
print(myaptable)

<class 'astropy.table.table.Table'>
   RA     DEC  
------- -------
0186 46.7304
2887 40.4703
886 21.3377
002 21.9679
057 40.6372
7 22.0116
785 14.2922
751 17.8168
039  15.327
542 30.7317
913 28.8959
026 41.5011
577 43.8511
963 38.1821
556 15.6214
967 42.7421
693 12.8502
489 20.8057
519 20.8014
088 18.2002
235 6.64845
83 37.3012

Then convert this to a VOTableFile object which contains a nested set of resources and tables (in this case, only one of each)#

myvotablefile = apvot.from_table(myaptable)
print(type(myvotablefile))

for r in myvotablefile.resources:
    mytable=r
    for t in r.tables:
        print(t)

<class 'astropy.io.votable.tree.VOTableFile'>
   RA     DEC  
------- -------
0186 46.7304
2887 40.4703
886 21.3377
002 21.9679
057 40.6372
7 22.0116
785 14.2922
751 17.8168
039  15.327
542 30.7317
913 28.8959
026 41.5011
577 43.8511
963 38.1821
556 15.6214
967 42.7421
693 12.8502
489 20.8057
519 20.8014
088 18.2002
235 6.64845
83 37.3012