snippet.py

def _insert_in_metadata_fits_safe(meta, key, value):
    """Helper function to insert key-value pair into metadata in a way that
       FITS can serialize
    Parameters
    ----------
    key : str
        Key to be inserted in the dictionary
    value : str or None
        Value to be inserted
    Notes
    -----
    This addresses a shortcoming of the FITS standard. There are length
        restrictions on both the ``key`` (8 characters) and ``value`` (72
        characters) in the FITS standard. There is a convention for handling
        long keywords and a convention for handling long values, but the
        two conventions cannot be used at the same time.
        This addresses that case by checking the length of the ``key`` and
        ``value`` and, if necessary, shortening the key.
    Reference
    ---------
    This helper method is taken from `astropy.nddata.cddata`. Not imported
    as this is a private method, subject to change
    """

    if len(key) > 8 and len(value) > 72:
        short_name = key[:8]
        meta['HIERARCH {0}'.format(key.upper())] = (short_name, "Shortened name for {}".format(key))
        meta[short_name] = value
    else:
        meta[key] = value