c extension finding the module in object initialization

[Marc-Andre Lemburg]

Hi Robin,

seeing that no one replied to your question, I'd suggest to ask this
on the Python C-API ML:

https://mail.python.org/mailman3/lists/capi-sig.python.org/

That's where the experts are, including the ones who implemented
the mutli-phase logic.

Cheers,
-- 
Marc-Andre Lemburg
eGenix.com

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On 21.09.2021 14:08, Robin Becker wrote:
> I have a c extension which is intended to implement a module the looks
> structurally like this
> 
> 
> ############
> a = 1
> b = 2
> 
> class T:
>     def __init__(self):
>         self.a = a
>         self.b = b
> ############
> 
> so when an object of type T is instantiated it can set up defaults based on the
> current module values of a and b.
> 
> In the past using old style single phase module creation the init function for
> the type could look up the module by using the PyState_FindModule function. In
> the new world where we can implement c extensions which might work with multiple
> interpreters (multi-phase creation). The docs say PyState_FindModule won't work
> for those and indeed it returns NULL so is useless.
> 
> Is there a way I can set the current module onto the type definition during the
> module's exec function? I thought it would be easy to add at the point in the
> exec where I'm doing this to the module, m,
> 
> TType.tp_base = &PyBaseObject_Type;
> if(PyType_Ready(&TType)<0) goto fail;
> if(PyModule_AddObject(m,"T", (PyObject *)&TType)<0) goto fail;
> 
> but I don't see the place in the type where I can add these sorts of dynamic
> attributes. The basic_size is for the created objects.
> 
> The created type does have a __dict__ which is a mappingproxy. I wondered when
> that actually gets instantiated.
> 
> I can see that the type has a __module__ attribute after the module is imported
> and I suppose if I can find the 'current' interpreter I might use the __module__
> to locate the module object via PyImport_GetModuleDict.
> 
> Any expertise or advice gratefully received.
> -- 
> Robin Becker
>