On Jan 14, 5:39 pm, Ben Finney <[EMAIL PROTECTED]> wrote: > I think of NotImplemented as equivalent to None; it's useful as a > sentinel value to set an attribute to in (e.g.) an abstract class.
My guess would be that it is more of an implementation performance decision than semantic. Checking 'if result is NotImplemented' is much faster than guarding the call with a try/except NotImplementedError block, and since the motivation for NotImplemented was AFAIK rich comparisons, the potential overhead could be substantial (e.g. a tight 'while i<j' loop that's executed millions of times). Semantically though, 'return NotImplemented' looks odd compared to 'raise NotImplementedError'. George -- http://mail.python.org/mailman/listinfo/python-list
