PyConstraint access data other than Matrix

Is there a way to access data of an owner and its targets other than its loc/rot/scale matrix? It seems like I could include a string option to enter the names of the owner and its targets, but then I’d have to type each object twice, and there would probably be errors if the names don’t match, so it would be nice if there was another way (though I guess it wouldn’t be too bad if there wasn’t).