[AstroPy] Accessing a FITS table generates "ValueError: Inconsistent data column lengths: set([0, 27645])"

[Daniel Evans]

> [...] column 12 has zero width, i.e. shape (0, nrow). If that’s actually
allowed by the FITS standard

>From my non-expert reading of the standard, v4 Sect. 7.3.1, it looks to be
explicitly permitted:

"The repeat count *r* is the ASCII representation of a non-negative integer
specifying the number of elements in field n. The default value of *r* is
1; the repeat count need not be present if it has the default value. A zero
element count, indicating an empty field, is permitted."

Regards,
Daniel

On 17 April 2018 at 13:52, Derek Homeier <
derek at astro.physik.uni-goettingen.de> wrote:

> On 17. Apr 2018, at 12:53 PM, Jordan Alexander <jordan.alexander at aut.ac.nz>
> wrote:
> >
> > First, thank you astropy for this outstanding package.  It played an
> important role in the completion of my PhD; much respect :)
> >
> > Using python 2.7.12 &  astropy 2.0.5 and following Lia R. Corrales'
> useful tutorial,
> >
> > http://www.astropy.org/astropy-tutorials/FITS-tables.html
> >
> > I am trying to access data stored in a FITS table, which generates
> >
> > ValueError: Inconsistent data column lengths: set([0, 27645])"
> >
> > Below are my steps and intermediate results that leads to this error...
> >
> > Can you please help here, astropy at python.org?
> >
> > P.S. I am able to access other tables in the following FITS file, just
> not the one I am interested in...
> >
> > --------
> >
> > from astropy.io import fits
> >
> > from astropy.table import Table
> >
> > hdulist = fits.open('WS001H.0.bin0000.source0000.FITS')
> >
> > hdulist.info()
> >
> > <generates the following output...>
> > Filename: WS001H.0.bin0000.source0000.FITS
> > No.    Name      Ver    Type      Cards   Dimensions   Format
> >   0  PRIMARY       1 GroupsHDU       51   ()      0 Groups  0 Parameters
> >   1  ARRAY_GEOMETRY    1 BinTableHDU     53   2R x 7C   [8A, 3D, 3E, 0D,
> 1J, 1J, 3E]
> >   2  SOURCE        1 BinTableHDU     89   3R x 26C   [1J, 16A, 1J, 4A,
> 1J, 8E, 8E, 8E, 8E, 8E, 8D, 1D, 1D, 8A, 1D, 1D, 8D, 8A, 8A, 8D, 1D, 1D, 1E,
> 1D, 1D, 1D]
> >   3  ANTENNA       1 BinTableHDU     52   18R x 13C   [1D, 1E, 8A, 1J,
> 1J, 1J, 1J, 1A, 8E, 8E, 1A, 8E, 8E]
> >   4  FREQUENCY     1 BinTableHDU     35   1R x 6C   [1J, 8D, 8E, 8E, 8J,
> 8J]
> >   5  INTERFEROMETER_MODEL    1 BinTableHDU     83   946R x 20C   [1D,
> 1E, 1J, 1J, 1J, 1J, 1E, 8E, 48D, 6D, 48D, 6D, 1E, 1E, 48D, 6D, 48D, 6D, 1E,
> 1E]
> >   6  CALC          1 BinTableHDU     75   5R x 11C   ['1D', '1D', '1D',
> '1D', '1A', '2D', '1A', '1D', '1D', '1D', '1D']
> >   7  MODEL_COMPS    1 BinTableHDU     86   946R x 21C   ['1D', '1J',
> '1J', '1J', '1J', '1D', '1D', '1D', '1D', '1D', '1D', '8E', '8E', '1E',
> '1E', '1D', '1D', '8E', '8E', '1E', '1E']
> >   8  UV_DATA       1 BinTableHDU     93   27645R x 13C   ['1E', '1E',
> '1E', '1D', '1D', '1J', '1J', '1J', '1J', '1E', '32E', '0J', '4096E']
> >
> That’s a somewhat unusual, if not pathological, table shape in HDU 8 -
> column 12 has zero width, i.e. shape (0, nrow).
> If that’s actually allowed by the FITS standard, it might be a bug, as
> astropy apparently converts this into a column of
> length 0 (instead of a shape=(0, ), length nrow=27645 column) which then
> fails in initialising the table.
> Can you read hdulist[1].data (which has a zero width column as well)?
>
> Cheers,
>                                 Derek
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