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

Nick Coghlan ncoghlan at gmail.com
Sun Aug 11 13:04:40 CEST 2013

On 11 August 2013 06:33, Antoine Pitrou <solipsis at pitrou.net> wrote:
> So code can be written like:
>   PyObject *dialects = PyState_GetModuleAttr(
>       &_csvmodule, "dialects", &PyDict_Type);
>   if (dialects == NULL)
>       return NULL;

This sounds like a good near term solution to me.

Longer term, I think there may be value in providing a richer
extension module initialisation API that lets extension modules be
represented as module *subclasses* in sys.modules, since that would
get us to a position where it is possible to have *multiple* instances
of an extension module in the *same* subinterpreter by holding on to
external references after removing them from sys.modules (which is
what we do in the test suite for pure Python modules). Enabling that
also ties into the question of passing info to the extension module
about how it is being loaded (e.g. as a submodule of a larger
package), as well as allowing extension modules to cleanly handle
reload(). However, that's dependent on the ModuleSpec idea we're
currently thrashing out on import-sig (and should be able to bring to
python-dev soon), and I think getting that integrated at all will be
ambitious enough for 3.4 - using it to improve extension module
handling would then be a project for 3.5.


Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia

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