2010/8/24 Hrvoje Niksic email@example.com:
The __length_hint__ lookup expects either no exception or AttributeError, and will propagate others. I'm not sure if this is a bug. On the one hand, throwing anything except AttributeError from __getattr__ is bad style (which is why we fixed the bug by deriving our business exception from AttributeError), but the __length_hint__ check is supposed to be an internal optimization completely invisible to the caller of list().
__length_hint__ is internal and undocumented, so it can do whatever it wants.