David and Stefan, you're both missing my main point which is the fact that the presence of the global declaration in the parent (g) **blocks the access to the grand parent context**, which would be accessible without this global declaration (of another variable since that one is global. It just happen to have the same name) in g; and the stackoverflow post also ignores this question.

I do not disagree that this might be a desired feature (we might wish to reject this because of the potential confusion caused by this kind of name collision situation), but without any clear specification on it (since this point doesn't seem to have been discussed in the (or any?) PEP), it could always be challenged as a design flaw.