[Python-Dev] Strange artifacts with PEP 3121 and monkey-patching sys.modules (in csv, ElementTree and others)

[Antoine Pitrou]

On Sat, 10 Aug 2013 18:06:02 -0700
Eli Bendersky <eliben at gmail.com> wrote:
> This solution has problems. For example, in the case of ET it would
> preclude testing what happens when pyexpat is disabled (remember we were
> discussing this...). This is because there would be no real way to create
> new instances of such modules (they would all cache themselves in the init
> function - similarly to what ET now does in trunk, because otherwise some
> of its global-dependent crazy tests fail).
> 
> A more radical solution would be to *really* have multiple instances of
> state per sub-interpreter. Well, they already exist -- it's
> PyState_FindModule which is the problematic one because it only remembers
> the last one.

I'm not sure I understand your diagnosis. modules_per_index (and
PyState_FindModule) is per-interpreter so we already have a
per-interpreter state here. Something else must be interferring.

Note that module state is just a field attached to the module object
("void *md_state" in PyModuleObject). It's really the extension modules
which are per-interpreter, which is a good thing.

Regards

Antoine.