Picking up this thread as part of the PEP 562 and PEP 549 review. I like PEP 562 most, but I propose to add special-casing for `__dir__`. Not quite as proposed above (making the C level module_dir() look for `__all__`) but a bit more general -- making module_dir() look for `__dir__` and call that if present and callable. Ivan what do you think of that idea? It should be simple to add to your existing implementation. (https://github.com/ilevkivskyi/cpython/pull/3#issuecomment-343591293)

On Tue, Sep 12, 2017 at 1:26 AM, Ivan Levkivskyi <levkivskyi@gmail.com> wrote:
> module.__getattr__ works pretty well for normal access, after being
> imported by another module, but it doesn't properly trigger loading by
> functions defined in the module's own namespace.

The idea of my PEP is to be very simple (both semantically and in terms
of implementation). This is why I don't want to add any complex logic.
People who will want to use __getattr__ for lazy loading still can do this
by importing submodules.

@Nathaniel @INADA
> The main two use cases I know of for this and PEP 549 are lazy imports
> of submodules, and deprecating attributes.

Yes, lazy loading seems to be a popular idea :-)
I will add the simple recipe by Inada to the PEP since it will already work.

> I still think the better way
> to solve the custom dir()  would be to change the module __dir__
> method to check if __all__ is defined and use it to generate the
> result if it exists. This seems like a logical enhancement to me,
> and I'm planning on writing a patch to implement this. Whether it
> would be accepted is still an open issue though.

This seems a reasonable rule to me, I can also make this patch if
you will not have time.

What do you think about the above idea?


--Guido van Rossum (python.org/~guido)