Code to find the differences in FITS headers and tabulate them in markdown table

diffheader.py

from itertools import product
import argparse
import numpy as np
from astropy.io import fits

parser = argparse.ArgumentParser()
parser.add_argument('files',nargs='+')
parser.add_argument('-e','--ext',default='0')
parser.add_argument('-o',default='hdrdiff.md')
args = parser.parse_args()

def parse_tsi(s):
    s = s.strip()
    if s[0] == '(' and s[-1] == ')':
        return tuple(parse_tsi(i) for i in s[1:-1].split(',') if i != '') 
    if s[0] == '\'' and s[-1] == '\'':
        return s[1:-1]
    try:
        return int(s)
    except ValueError:
        raise ValueError('\'{}\' can\'t be parsed as str, int or tuple'.format(s))

ext = parse_tsi(args.ext)
hdrs = [fits.getheader(fn,ext) for fn in args.files]
nhdrs = len(hdrs)

diffkeys = []
for i in range(nhdrs-1):
    for j in range(i+1,nhdrs):
        diffkeysij = fits.HeaderDiff(hdrs[i],hdrs[j],ignore_keywords=diffkeys)
        diffkeys.extend(diffkeysij.diff_keyword_values.keys())
        diffkeys.extend(diffkeysij.diff_keywords)

diffkeys = [key for key in diffkeys if key not in ('HISTORY','COMMENT','HIERARCH')]
nkeys = len(diffkeys)

vals = [['' if key not in hdr else str(hdr[key]) for hdr in hdrs] for key in diffkeys]

with open(args.o,'w') as f:
    f.write('| | ' + ' | '.join([file_.split('.')[0] for file_ in args.files]) + ' |\n')
    f.write('| ---- |' + ' ---: |'*nhdrs + '\n')
    for i in range(nkeys):
        f.write('| ' + diffkeys[i] + ' | ' + ' | '.join([vals[i][j] for j in range(nhdrs)]) +' |\n')