Each ColumnAttribute
may have a validator
method defined on it. This validates values set on this attribute to ensure that they meet the FITS standard. Invalid values will raise a warning and will not be used in formatting the column. The validator should take two arguments--the Column
it is being assigned to, and the new value for the attribute, and it must raise an :None:None:`AssertionError` if the value is invalid.
The ColumnAttribute
itself is a decorator that can be used to define the validator
for each column attribute. For example:
@ColumnAttribute('TTYPE')
def name(col, name):
if not isinstance(name, str):
raise AssertionError
The actual object returned by this decorator is the ColumnAttribute
instance though, not the name
function. As such name
is not a method of the class it is defined in.
The setter for ColumnAttribute
also updates the header of any table HDU this column is attached to in order to reflect the change. The validator
should ensure that the value is valid for inclusion in a FITS header.
Descriptor for attributes of Column
that are associated with keywords in the FITS header and describe properties of the column as specified in the FITS standard.
The following pages refer to to this document either explicitly or contain code examples using this.
astropy.io.fits.column.ColumnAttribute
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