(Serious?) package namespace problem (and a proposal)

[Gordon McMillan]

Huaiyu Zhu wrote: 

>Given the following directory structure,
>
>python/
>   AAA.py
>   BBB/
>      __init__.py
>      AAA.py
>      
>if sys.path contains 'python', then 
>
>from AAA import *
>from BBB.AAA import * 
>
>would do the right thing at most locations, except when pwd is python/
>and when '.' is before 'python' in sys.path, in which case they both
>import from python/AAA.py.
>Is this a fair description of current situation?

There's a problem (actually a couple) but this isn't the right description. 
If you're in python/BBB then "import AAA" and "import BBB.AAA" both get 
BBB.AAA.

>...If so this makes
>package name spaces essentially flat. That is, in order to avoid name
>clashes one has to avoid identical module names even if they are buried
>deep inside packages.  

Yes, (except I wouldn't call that "flat" - I would interpret "flat" as no 
subpackages).

>This is even worse on Windows - its file names
>are caseless - as one has to avoid filenames with different cases as
>well. 

Too true...

>This situation occurs quite often in practice.  For example, AAA could
>be a module for doing something.  BBB could be a wrapper package for
>doing things somewhat differently.  So within BBB/AAA.py one calls
>'import AAA' to get the real job done, and oops, it imports itself!

Besides avoiding using the same name, you could make the top level a 
package, then python.BBB.AAA could import python.AAA and it would be 
completely unambiguous. Which is a good reason to avoid relative imports - 
they are by nature ambiguous.

>Although it is not advisable to put '.' in path, especially at front, a
>lot of people actually do. And the functionality of a package should not
>depend on this detail.  Otherwise what happens if one imports several
>packages each expecting a different ordering of sys.path?

Actually it is very useful, since it allows you to have a script have some 
private support modules that don't clutter up sys.path for other scripts.

>So now to my proposed solution.  Is it possible to have something like
>this? 
>
>sys.rootpath  = ['/usr/lib/python1.5',
>'/usr/lib/python1.5/site-packages'] from rootpath.AAA import *
>from rootpath.BBB.AAA.import *

You could use Greg Stein's imputils, but in this case just packagizing the 
whole thing is a more straightforward solution.

- Gordon