[Python-Dev] advice needed: best approach to enabling "metamodules"?

[Petr Viktorin]

On Sun, Nov 30, 2014 at 12:05 AM, Steven D'Aprano <steve at pearwood.info> wrote:
> On Sun, Nov 30, 2014 at 11:07:57AM +1300, Greg Ewing wrote:
>> Nathaniel Smith wrote:
>> >So pkgname/__new__.py might look like:
>> >
>> >    import sys
>> >    from pkgname._metamodule import MyModuleSubtype
>> >    sys.modules[__name__] = MyModuleSubtype(__name__, docstring)
>> >
>> >To start with, the 'from
>> >pkgname._metamodule ...' line is an infinite loop,
>>
>> Why does MyModuleSubtype have to be imported from pkgname?
>> It would make more sense for it to be defined directly in
>> __new__.py, wouldn't it? Isn't the purpose of separating
>> stuff out into __new__.py precisely to avoid circularities
>> like that?
>
> Perhaps I'm missing something, but won't that imply that every module
> which wants to use a "special" module type has to re-invent the wheel?
>
> If this feature is going to be used, I would expect to be able to re-use
> pre-written module types. E.g. having written "module with properties"
> (so to speak) once, I can just import it and use it in my next project.

I expect you'd package the special metamodule class in a stand-alone
package, not directly in the ones that use it.
You could import other packages freely, just the one that you're
currently defining would be unavailable.