[Python-Dev] [Python-checkins] r43033 - in python/trunk/Lib: distutils/sysconfig.py encodings/__init__.py

[Guido van Rossum]

Because Thomas designed it this way. :-)

I believe his design makes sense though: "import foo" translates to
__import__(foo, ...).

There's a separate setting, only known to the compiler, that says
whether "from __future__ import absolute_import" is in effect (there's
no way to slip a flag into globals to convey this setting, since code
is compiled independently from globals, and there are ways to pass
flags to the compiler without explicitly doing the future import).

So the compiler emits different code when the future syntax is in
effect, and that opcode must pass its knowledge to __import__. This is
done trough the 5th argument, which also tells us how many leading
dots there were. Without the future import, the 5th argument is
omitted (as long as there aren't any leading dots).

--Guido

On 3/15/06, Phillip J. Eby <pje at telecommunity.com> wrote:
> At 10:33 AM 3/15/2006 -0800, Guido van Rossum wrote:
> >Well, absolute imports without the future statement will not use the
> >5th argument, so they won't break, right? That's what MAL also says.
> >Someone please fix this.
>
> Why is a 5th argument needed to do absolute imports?  Shouldn't it suffice
> to supply a globals argument with no __path__ and an undotted
> __name__?  ISTM that passing in the builtins dictionary as the globals
> argument ought to do the trick.
>
>


--
--Guido van Rossum (home page: http://www.python.org/~guido/)