[Python-Dev] iterzip()

[Tim Peters]

[martin@v.loewis.de]
> I'd suggest a tp_is_immutable predicate. If a container is immutable
> and non-cyclic, it can be untracked. A container is non-cyclic if all
> contained objects are either non-gc, or untracked.

And none of the contained objects are NULL (else the scheme doesn't even
work for tuples).

How do you know which other objects it contains?  Calling tp_traverse and
seeing whether that ever calls the passed-in visit function doesn't work
(see the already-repeated discussion about this for tuples).