[Python-Dev] this is what happens if you freeze all the modules required for startup

[Brett Cannon]

On Wed Apr 16 2014 at 4:53:25 PM, Terry Reedy <tjreedy at udel.edu> wrote:

>  > On Wednesday, April 16, 2014 2:57:35 PM, Terry Reedy <tjreedy at udel.edu
>  > <mailto:tjreedy at udel.edu>> wrote:
>
>  >     PS. In the user process sys.modules, there are numerous null
>  >     entries like these:
>  >       >>> sys.modules['idlelib.os']
>  >       >>> sys.modules['idlelib.tokenize'__]
>  >       >>> sys.modules['idlelib.io <http://idlelib.io>']
>  >       >>> <etcetera>
>
> On 4/16/2014 3:10 PM, Dr. Brett Cannon wrote:
> > Is this Python 2 or 3?
>
> Py 2. I should have said so. The entries do not appear in py3.
>
> > In Python 2 it means an attempt to perform a relative import failed but
> > an absolute in succeeded, e.g. from idlelib you imported os, so import
>  > tried idlelib.os and then  os.
>
> *I* have not done anything. For tokenize, for instance, the existing
> code just does what I though were absolute imports, in 2 files.
>    import tokenize
>

That's not an absolute import if it's within a package and you didn't
declare `from __future__ import absolute_import`.


>
> Perhaps the extra entries have something to do with the fact that these
> startup imports are invisible to user code, just like those done by the
> interpreter itself on startup. 2.7 uses spawnv (and 3.4 uses subprocces)
> to run something like one of the following.
>    python -c "__import__('idlelib.run').run.main(False)"
>    python -c "__import__('run').main(False)"
>

Nope, it has to simply do with how Python 2 does implicit relative imports.
Add the __future__ statement and they will go away.

-Brett


>
> run.py has several normal lines with
>    import <stdlib module>
>    from idlelib import <idlelib module>
> and ditto for some of the imported idlelib modules.
>
>  > You should definitely consider using a future import to guarantee
> > absolute imports.
>
> --
> Terry Jan Reedy
>
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