[Python-ideas] Implicit submodule imports

[Ethan Furman]

On 09/26/2014 11:15 AM, Nathaniel Smith wrote:
>
> Option 1: allocate a new object, shallowly copy over all the old object properties into the new one, and then find all
> references to the old object and replace them with the new object. This is possible right now, but error prone: cloning
> a module object requires intimate knowledge of which fields exist, and swapping all the references requires that we be
> careful to perform the swap very early, when the only reference is the one in sys.modules.
>
> Option 2: the __class__ switcheroo. This avoids the two issues above. In exchange it's fairly brain-hurty.
>
> Option 3: Oh wait, I just thought of a third option. It only works for packages, but that's okay, you can always convert a module
> into a package by a simple mechanical transformation. The proposal is that before exec'ing __init__.py, we check for the
> existence of a __preinit__.py, and if found we do something like
>
> sys.modules[package] = sentinel to block circular imports
> namespace = {}
> exec __preinit__.py in namespace
> cls = namespace.get("__metamodule___", ModuleType)
> mod = cls(name, doc, namespace)
> sys.modules[package] = mod
> exec __init__.py in namespace
>
> So preinit runs in the same namespace as init, but with a special restriction that if it tries to (directly or
> indirectly) import the current package, then this will trigger an ImportError. This is somewhat restrictive, but it does
> allow arbitrary code to be run before the module object is created.

What about

   Option 4: have reload work with modules converted into classes

?

This may mean having some extra fields in the class, and probably some extra code in the module loading, but it might be 
the simplest approach.

--
~Ethan~