[Python-Dev] Module renaming and pickle mechanisms

[M.-A. Lemburg]

On 2008-05-19 21:26, Brett Cannon wrote:
>> It is possible to make pickle aware of the module renames, but
>> that doesn't solve problems with other forms of serialization
>> or use of the .__module__ attribute in general.
>>
>> Why can't we just provide a "from __future__ import renamed_modules"
>> which then provides all the new name to old name mappings in
>> some form (e.g. module proxies or whatever) and leave the
>> existing modules in 2.x untouched ?
> 
> I have started a discussion on the stdlib SIG on how to handle this,
> so I will defer this discussion to there.

Thanks.

> But one thing that needs to be decided is if we are ever going to
> allow ourselves to rename modules without a major version bump, and if
> so how to deal with this problem. I would hope we don't have to wait
> another eight years before there is another chance to shift things
> around if it becomes apparent that some new package should be
> introduced since 2to3 gives us a very nice way to handle the
> mechanical aspect of porting code.

We could some kind of module aliasing support to Python.

Backporting name changes would then be a matter of loading
the right aliasing map into the older Python version.

This could probably be done by adding a line

if hasattr(sys, 'module_aliases'):
     modname = sys.module_aliases.get(modname, modname)

to the __import__ implementation.

By turning .__module__ into a property and applying the same
aliasing there, we should be able to resolve most technical
issues with a renaming.

Alas, too late to change 2.4 and 2.5 :-/

-- 
Marc-Andre Lemburg
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