[AstroPy] Re: functional interface for PyFITS?

Andrew Ptak ptak at pha.jhu.edu
Tue Mar 22 09:51:05 CST 2005

I missed the original post so I'm sorry if this was already mentioned, 
but in fairness I just want to add that this format for selecting 
extensions has been in use for a while in high-energy fits software, most 
notably ftools and ciao.  For both of these, you can give either the name 
of the extension or the extension number in brackets.  So that format is 
"natural" for some of us, and might help with converting shell scripts to 
pure python.  I wonder if there is anything in the fits standard 
concerning filenames. But of course this is a minor issue and not allowing 
it would be ok.

Andy Ptak

On Tue, 22 Mar 2005, John Blakeslee wrote:

> > > img=getdata('foo.fits[2]')  for the 2nd extension, as a valid alternative
> > 
> > Be careful here.  How do you distinguish that from a file whose name
> > is literally foo.fits[2]?  And if you do 'foo.fits'[2], how do you
> > distinguish that from the second element of a string array (bar, in
> > this case): getdata(bar[2])?  The first is contrived but possible in
> > the grand universe of file-naming schemes.  The second I use *all the
> > time* to address a list of filenames in sequence.  Stick with
> > getdata('foo.fits', ext=2).  It's just a few extra characters longer
> > than the shorthand, and is much clearer.
> I want to agree whole-heartedly with this comment!
> We use pyfits a lot and find it amazingly useful,
> and the syntax fairly clear and consistent.  Allowing
> something like 'foo.fits[2]' in a function call to 
> refer to the 2nd extenstion in the file would open
> a Pandora's box of inconsistency and confusion, or 
> at least set a very bad precedent.
> JB
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