[Python-Dev] New universal import mechanism ( Re: [Python-checkins] python/dist/src/Python import.c,2.210,2.211)

[Greg Ward]

On 02 December 2002, Just van Rossum said:
> I don't follow. In my scheme (which in the meantime I've partially
> implemented) any first import will be done by an import hook on
> sys.import_hooks, so you have full control.

Ahh!  I get it, sorry.  Makes sense now.

> If you mean that you can't
> hook imports that are already in sys.modules: yes, that's a feature

Agreed.  Once something has been imported, the import hooks should not
be bothered with it again.

>     - sys.import_hooks is a list of hooks
>     - a hook is a callable object taking two arguments:
>       [sub]modulename and path. Path is either the parents package's
>       __path__ or None.
>     - a hook either returns None ("module not found") or a two-tuple:
>       (loadfunc, cookie). loadfunc is a callable object that will

Sounds sensible, but please s/cookie/data/ (or similar).

>       be called with two arguments: the fullname and "cookie". The
>       cookie is just an arbitrary object, private to the hook. The
>       loaderfunc must return the imported module.
>     - (Currently it expects that the loaderfunc will insert the module
>       in sys.path, I'm not sure I like that. Actually, I am sure I
               ^^^^

You really meant sys.module, right? 

>       don't like that <wink>, but changing that would require more
>       changes to import.c that I'd like. I'll have to investigate.)

I agree: if an import hook is not responsible for checking sys.modules
before doing an import, it should not be responsible for updating
sys.modules after an import.

        Greg
-- 
Greg Ward <gward@python.net>                         http://www.gerg.ca/
Clarke's Law:
Any sufficiently advanced technology is indistinguishable from magic.