Astropy

astropy.io.fits

>>> hdulist = fits.open('input.fits')
>>> hdulist.info()

• each element of an HDUList is an HDU object with .header and .data attributes, which can be used to access the header and data portions of the HDU.

>>> hdulist[0].header['targname']

• To see the entire header as it appears in the FITS file (with the END card and padding stripped), simply enter the header object by itself, or print(repr(header)):
• It’s also possible to view a slice of the header:

>>> header[:2]

• Another way to either update an existing card or append a new one is to use the Header.set() method:

>>> prihdr.set('observer', 'Edwin Hubble')