> The patch does not seem to walk the mro to look for slots in base 
> classes.  Also, an instance with a __dict__ attribute may also have 
>attributes stored in slots.
Well, what I am doing is more or less the equivalent of 

return object.__slots__ if hasattr(object, '__slots') else object.__dict__

and this is coherent with the updated documentation. The one you proposed is an alternative behavior; am I supposed to follow that one?

>
> BTW, copyreg._slotnames(cls) properly calculates the slot names for cls and tries to cache them as cls.__slotnames__.  Pickle does the equivalent of
>
>     try:
>         slotnames = cls.__slotnames__
>     except AttributeError:
>         slotnames = copyreg._slotnames(cls)
thanks! I'll take into account. 

-- 
ù