[Python-Dev] Relative Package Imports

Jim Fulton jim@digicool.com
Wed, 15 Sep 1999 15:59:10 -0400

"James C. Ahlstrom" wrote:
> Jim Fulton wrote:
> > In this context, consider the following concrete, though fictional
> > example.
> > ............
> The classical solution would be to add "Shared" to sys.path.  But
> how to do this?  And what if another installation changes it?

This doesn't work, because 'Shared' has sub-packages by organization.

> > I'd be curious to hear how folks would solve this problem.
> 1) Ship a custom binary interpreter with critical modules frozen in,
> and which sets a custom sys.path before anything else happens.  So
> you are not dependent at all on PYTHONPATH.  Currently this works.

This is what we do for our binary distribtions, but it doesn't do
anything for third-party products added to Zope.

> 2) Add a new command line option which sets sys.path and always use
> it to start your app.  It lists only critical zope directories so
> zope has its own private name space.

We have a start script that takes care of this.  This gets Zope's 
top-level names (of which there are too many already) into the
path.  This doesn't help with third-party products added to Zope.
> 3) Add your own import hooks using imputil.py and boot it as
> in (1).

But imputil has a global effect. I suppose I could implement
what I want with imputil or by otherwise creating my own importer
using the standard import hooks.  I suspect that's what I'll
have to do eventually.

>  Better if it were part of Python. 
> 4) Use a new Python.pyl file which has seeking from the end and
> thus allows concattenation of multiple *.pyl.  Each package is
> a foo.pyl, bar.pyl, and to distribute an app, you concatenate
> packages.  The implied PYTHONPATH in each *.pyl file is "."
> except perhaps for the Python lib which is "Lib".  Boot it as
> in (3).

I'm not looking for a way to replace the current package scheme.
Also, I'm not just looking at an app, but at an app that
contains apps (aka components).
> > Personally, I'd like the problem to go away. :)
> I have the same problem, so me too.
> > I'd like the Python
> > import rules to change to make this solvable without import hooks or
> > path hacking.  I can think of two ways to approach this:
> >
> >   - Relative parent imports:
> >
> >       import __.kjParsing.kjParser
> OK by me, but doesn't solve the Grand Problem.
> >   - Gradually less local searches.
> I am currently bewildered by Python's import mechanism, and
> this may push me into brain damage.  Well, *more* brain damage.

I don't see what's so complicated.  You just use a gradually
widening search, rather than an immediately widening search.
I don't think that this is any more complicated than the current

I actually prefer the second apprach because it doesn't require any
code changes to take advantage of it.  I may implement it for Zope
if nothing is done in standard Python.


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