[AstroPy] Equivalent expression for SXPAR from IDL in python

[Paul Barrett]

astropy.io.fits.open(filename)[0]['NAXIS1'] will give you the value of the
NAXSI1 keyword in the primary header.

In the Python FITS library, a FITS file is a list of headers and each
header is a list of rows.  The value of a keyword can be obtained by
specifying the header name or index, and the keyword name as show above.


On Sun, Feb 14, 2016 at 7:47 AM, Roberts, Michael <
michael.roberts.15 at ucl.ac.uk> wrote:

> I'm hoping this question is relatively straightforward for those
> proficient with IDL and python and fits file handling (I'm using
> the astropy.fits module)
>
>
> I'm looking to find an equivalent to SXPAR (whose function is to obtain
> the value of a parameter in a FITS header) from IDL into python...
>
>
> http://idlastro.gsfc.nasa.gov/ftp/pro/fits/sxpar.pro
> "sxpar.pro" - idlastro.gsfc.nasa.gov
> <http://idlastro.gsfc.nasa.gov/ftp/pro/fits/sxpar.pro>
> idlastro.gsfc.nasa.gov
> Apostrophes are stripped ; from strings. If the parameter is logical, 1b
> is ; returned for T, and 0b is returned for F. ; If Name was of ...
>
> This is the original code in IDL:
>
> nxpix_uw1_ext1 = sxpar(hima_sk_uw1_ext1,'NAXIS1')
>
> nypix_uw1_ext1 = sxpar(hima_sk_uw1_ext1,'NAXIS2')
>
> This is my conversion attempt into python using astropy.fits:
>
> from astropy.io import fits
>
>
> hima_sk_um2 = fits.open('') #Will contain the directory extension to the
> fits/img file I wish to open
>
>
> # Compute the size of the images (you can also do this manually rather
> than calling these keywords from the header):
>
> nxpix_um2_ext1 = hima_sk_um2[1].header['NAXIS1']
>
> nypix_um2_ext1 = hima_sk_um2[1].header['NAXIS2']
>
> Firstly, is this correct? And secondly, is this the best way to handle an
> extension value?
>
> Any advise would be warmly received.
>
> Many thanks,
>
> Michael
>
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