fitscphdr

#!/usr/bin/env python
from __future__ import print_function
import argparse
import warnings
from astropy.io import fits

# python 2/3 compatability
try:
    input = raw_input
except NameError:
    pass


def copy_header(fits_source, fits_target, clobber=False, interactive=True,
                fits_new=""):
    """Copy the header of fitsname to the header of outname.
    
    If a header entry would be overwritten and clobber is False,
    this will warn the user and fail to overwrite the header entry.

    Parameters
    ----------
    :fits_source: str, name of file from which to copy the header
    :fits_header: str, name of file to which to copy the header
    :clobber: bool, default False, if True then overwrite header entries
              without warning
    :interactive: bool, default True, if True (and clobber is set to True), 
                  prompt for overwrite
    :fits_new: str, default "", new fits file to write to

    Returns
    -------
    None
    """
    warning_str = ("FITS entry {} is already in {} and has value {}.")
    source_hdu = fits.open(fits_source)[0]
    source_header = source_hdu.header
    target_hdu = fits.open(fits_target)[0]
    target_header = target_hdu.header
    for key, value in source_header.items():
        if key.strip().lower() == 'comment':
            continue
        if key in target_header and not clobber:
            old_value = target_header[key]
            warnings.warn(warning_str.format(key, fits_target, old_value))
            if interactive:
                valid_response = False
                overwrite_entry = False
                while not valid_response:
                    print("Overwrite with {}? [y]/n?".format(value))
                    response = input()
                    response = response.strip().lower()
                    if response in ("y", "yes", ""):
                        valid_response = True
                        overwrite_entry = True
                    elif response in ("n", "no"):
                        valid_response = True
                        overwrite_entry = False
                    else:
                        warnings.warn("Invalid response, please choose [y]/n!")
                if overwrite_entry:
                    target_header[key] = value
        elif key in target_header and clobber:
            target_header[key] = value
        else:
            continue
    new_hdu = fits.PrimaryHDU(header=target_header, data=target_hdu.data)
    new_hdu.writeto(fits_new)


if __name__ == "__main__":

    parser = argparse.ArgumentParser(description='Copy a fits header.')
    parser.add_argument('sourcefits', action='store', type=str,
                        help='source fits header file')
    parser.add_argument('targetfits', action='store', type=str,
                        help='target fits header file')
    parser.add_argument('newfits', action='store', type=str,
                        help='name for new fits file')
    parser.add_argument('--clobber', action='store_true',
                        help='overwrite existing fits header entries')
    args = parser.parse_args()

    fits_source, fits_target, fits_new = args.sourcefits, args.targetfits, args.newfits
    clobber = args.clobber
    copy_header(fits_source, fits_target, clobber=clobber, fits_new=fits_new)