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

Huaiyu Zhu hzhu at knowledgetrack.com
Wed Jun 28 20:24:36 EDT 2000 
On 29 Jun 2000 01:56:19 +0200, Bernhard Herzog <herzog at online.de> wrote:
>
>If your cwd is python then the sys.path entry for python/ and '.' are
>the same directory. Why would that lead to problems? The only thing I
>can think of is that other directories in sys.path also have AAA
>modules.

Sorry I completely messed up my description.  (And apologies for complaining
about earlier correspondents not seeing the problem.)  Here's a retake:

$PYTHONPATH/
   AAA/
      __init__.py
   BBB/
      __init__.py
      aaa.py
      ccc.py
   CCC/
      ...

Within BBB/aaa.py the statement 'import AAA' imports from AAA/__init__.py on
Unix but from BBB/aaa.py on Windows.

The reason is that within the BBB package python first looks for a module
called AAA within the package (which it found as aaa.py on Windows) before
it looks for a package named AAA.

Although this is often the desired behavior, the other way around is also
fairly common.  In my case AAA and CCC are packages written by others and
BBB is a wraper pacakge that imports the other packages to do the real work
but provides different interfaces for convenience.  Using identical names
seems very natural here.

Since there is no way to tell python to go to absolute path first, one has
to make all module names in all packages distinct.  This IMHO defeats one of
the most important purpose of using packages, that is to encapsulate name
spaces for module names.

Therefore I think it is desirable for python to provide a mechanism for
programmers to describe absolute path of imports.  Like on Unix, writing
/bin/sh in stead of sh in a script will guarantee its behavior no matter
where it is run and what the current PATH the user has.

My previous proposal was to use
import pythonroot.AAA
but in analogy with Unix paths maybe a syntax like
import .AAA
is even better.  (BTW, this is the scheme used in DNS configurations for
distinguishing qualified and unqualified domain names.)

-- 
Huaiyu Zhu                       hzhu at users.sourceforge.net
Matrix for Python Project        http://MatPy.sourceforge.net
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