Hmmm...

Well, much as I hate to say it, it's sounding like the correct solution here is to have %o and %x work when __index__ is available, instead of the other way around.  :(

.format is not an issue because one must specify one's own if inheriting from object.

So the complete list of spcecifiers then is d, i, o, u, U, and c [1], and they should work if __index__ works.

Are we in agreement?


[1] http://docs.python.org/dev/library/stdtypes.html#printf-style-string-formatting