[AstroPy] Re: functional interface for PyFITS?: foo.fits[2]
Victoria G. Laidler
laidler at stsci.edu
Tue Mar 22 12:22:57 EST 2005
I've been googling a bit and have not yet found whether the FITS
standard either mandates or recommends support for the 'foo.fits[2]'
syntax to specify the extension.
In addition to ftools and ciao, IRAF also supports this method for
filename specification.
PyFITS does not support it presently.
Andrew Ptak wrote:
>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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>
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