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

[Antoine Pitrou]

On Sun, 30 Nov 2014 11:15:50 -0800
Guido van Rossum <guido at python.org> wrote:
> On Sun, Nov 30, 2014 at 6:15 AM, Brett Cannon <brett at python.org> wrote:
> >
> >  On Sat, Nov 29, 2014, 21:55 Guido van Rossum <guido at python.org> wrote:
> >
> > All the use cases seem to be about adding some kind of getattr hook to
> > modules. They all seem to involve modifying the CPython C code anyway. So
> > why not tackle that problem head-on and modify module_getattro() to look
> > for a global named __getattr__ and if it exists, call that instead of
> > raising AttributeError?
> >
> >  Not sure if anyone thought of it. :) Seems like a reasonable solution to
> > me. Be curious to know what the benchmark suite said the impact was.
> >
> Why would there be any impact? The __getattr__ hook would be similar to the
> one on classes -- it's only invoked at the point where otherwise
> AttributeError would be raised.

builtins are typically found by first looking up in the current globals
(module) scope, failing, and then falling back on __builtins__.

Depending on how much overhead is added to the "failing" step, there
/might/ be a performance difference. Of course, that would only occur
wherever a __getattr__ hook is defined.

Regards

Antoine.