[Python-Dev] __module__ of newly-created extension classes

[David Abrahams]

From: "Guido van Rossum" <guido@python.org>

> > The "current module" is given by the current formula
(PyEval_GetGlobals(),
> > etc.) except when loading an extension module, in which case the
current
> > module is the one most recently created.
>
> If the init function of an extension module calls PyImport_Import() to
> import another extension which has to be loaded freshly, does that
> mean that after that point the definition current module is left to
> that other module, or does it revert to the first extension?

It reverts of course (glad you asked)!

> What if an extension imports a Python module which loads an extension
> module?

Of course there's a similar reversion after the extension module finishes
loading.

> > I'm not sure, but this might be simplifiable to:
> >
> > the "current module" is the one most recently created.
>
> No, because in a Python function defined in a Python module, when that
> function is executing that module is the current module.
>
> A possible implementation could maintain a per-thread global which is
> NULL when we're not loading an extension.  Py_InitModule() sets this
> global to the module it creates.  When the import mechanism calls an
> extension's initxxx function, it saves the value of this per-thread
> global; when the function returns, it restores it from the saved
> value.  Then there could be a new function Py_GetGlobals() that looks
> in this per-thread global, and returns its dict if it is not NULL; if
> NULL, it falls back on PyEval_GetGlobals().  (You can't promise to
> return the current *module*, because that isn't kept track of; only
> the current globals are kept track of on the execution stack.)

Sounds pretty good to me.

-Dave