[AstroPy] Need Help about Astropy.table.Table.write

[Guang Yang]

Hi Peter,

Emitting a warning is great, just like when reading some non-standard wcs in fits header. 

Thanks,
Guang  


> -----Original email-----
> From: "Peter Teuben" <teuben at astro.umd.edu>
> Sent Time: Jul 25, 2014 8:19:43 PM
> To: "Astronomical Python mailing list" <astropy at scipy.org>
> Cc: 
> Subject: Re: [AstroPy] Need Help about Astropy.table.Table.write
> 
> Guang,
>    in your case I think you were done a service, so make 'ct' become
> "count", since the (FITS) community has decided this to be a better more
> descriptive word. Most non-english speakers might even have difficulties
> with "ct" so your desire to there be a future that can override the fits
> standard has to be take with caution, especially if the column has a 
> meaning we already agreed upon.
> 
> Perhaps the code can emit a warning and refer to the FITS resource where
> all the units are defined, or even spit out the ones the code knows
> about .... heaven forbid?
> 
> peter
> 
> On 07/25/2014 08:07 AM, Guang Yang wrote:
> > Hi Tom,
> >
> > Great, it works. Hope in the future there will be keywords that can overriede the fits standard constraints. 
> >
> > Thank you very much,
> > Guang
> >
> >
> >> -----Original email-----
> >> From: "Thomas Robitaille" <thomas.robitaille at gmail.com>
> >> Sent Time: Jul 25, 2014 6:59:21 PM
> >> To: "Astronomical Python mailing list" <astropy at scipy.org>
> >> Cc: 
> >> Subject: Re: [AstroPy] Need Help about Astropy.table.Table.write
> >>
> >> Hi Guang,
> >>
> >> To overwrite a file, you can use:
> >>
> >>   cat.write('new.fits', format='fits', overwrite=True)
> >>
> >> For the unit, the issue is that ``ct`` is not a valid unit according to
> >> the FITS standard. The 'correct' unit for FITS is ``count``. We may be
> >> overly strict at the moment in that Table.write will simply crash if a
> >> unit is not standard-compliant, when we could simply emit a warning and
> >> still write it out, so I will open an issue for that.
> >>
> >> So in the mean time, the solution is to do:
> >>
> >>   cat['name'].unit = 'count'
> >>
> >> where 'name' is the name of the problematic column. Do this before
> >> writing it out to FITS.
> >>
> >> Cheers,
> >> Tom
> >>
> >> Guang Yang wrote:
> >>> Hi All,
> >>>
> >>> I've found Astropy.table.Table.write is unable to write tables with arbitrary units. 
> >>> For example, after using sextractor to generate a fits table, 
> >>>
> >>> from astropy.table import Table
> >>> cat = Table.read('sextractor_output.fits', format='fits')
> >>> cat.write('new.fits', format='fits')
> >>>
> >>> Then, the error comes: Unit u'ct' is not part of the FITS standard. And I've found no parameter to avoid the unit problem.
> >>>
> >>> Also, when the file 'new.fits' already exists, there seems to be no keyword to overwrite the file.
> >>>
> >>> Thanks,
> >>> Guang Yang
> >>>
> >>>  
> >>>
> >>>
> >>>
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