C-API, tp_dictoffset vs tp_members

["Martin v. Löwis"]

>>>>> I have a predefined set of members, some of which are optional.
>>>> Having optional fields is also a good reason.
>>> What is the use of T_OBJECT_EX vs T_OBJECT in PyMemberDef then?
>> Right - this works for optional objects. However, it can't possibly
>> work for any of the other fields.
> 
> I have two members, one T_OBJECT and one T_OBJECT_EX. Both are NULL and both 
> still appear in the dir() output. For one, accessing it returns 'None', for 
> the other it raises an exception. I would have expected an element that is 
> not accessible, not even 'None', to also not be visible in dir().

I understood your expectation already. I maintain my theory that it
shows up because there is a descriptor on the class.

>> I suppose that's because there will still be a descriptor for the
>> field in the class.
> 
> So is that intentional or is it dir() that could be improved there? 

It's probably both.

> Should I file a bugreport?

Only if you can provide a patch also. My guess is that when you have
the patch completed, you might realize that it is not an improvement,
despite achieving what you wanted to achieve.

Regards,
Martin