[AstroPy] Read FITS headers without loading data
Gary Bernstein
garyb at physics.upenn.edu
Mon Sep 8 10:40:05 EDT 2014
I would like to extract the header information from a large multi-extension FITS file using astropy.io.fits. This runs very slowly, and I suspect because it is reading the data of each extension when the header is accessed e.g. via
import astropy.io.fits as pf
f = pf.open(‘mef.fits’)
for hdu in f:
h = hdu.header
… do stuff with header…
It is *much* faster using e.g. cfitsio utilities (<<1 second compared to 10’s of seconds for the above on a multiple-GB file). Am I correct that the data is being loaded for each extension in the above method? If so is there a workaround? Neither using getheader nor (un)setting memmap seems to make a difference.
Thanks,
Gary Bernstein
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