[Python-Dev] os.path.walk() lacks 'depth first' option (original) (raw)

Guido van Rossum guido@python.org
Mon, 12 May 2003 07:58:19 -0400

I like ValueError best when an input is of the right type but outside the defined domain of a function, like math.sqrt(-1.0) or chr(500). Failing to find something feels more like a (possibly proper subclass of) LookupError to me.

Yeah, [].remove(42) raising ValueError is a bit weird. It was put in before we had the concept of LookupError, and the rationale for using ValueError was that the value is not found -- can't use IndexError because the value is chosen from a different set than the index, can't use KeyError because lists don't have a concept of key. In retrospect, it would have been better to define a SearchError, subclassing LookupError.

OTOH there's something to say for fewer errors, not more; e.g. sometimes I wish AttributeError and TypeError were unified, because AttributeError usually means that an object isn't of the expected type.

--Guido van Rossum (home page: http://www.python.org/~guido/)