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

[Huaiyu Zhu]

On Wed, 28 Jun 2000 14:57:41 -0600, Bjorn Pettersen <bjorn at roguewave.com> wrote:
>Note that all the problems you describe completely go away if you do:
>
>  import AAA
>  import BBB.AAA
>
>IMHO you deserve any/all complications you get when you do "from foo
>import *", and I strongly believe that we shouldn't do _anything_ to
>encourage this use...
>

Noop.  The issue is not what names are imported from a package, but from
which package/module files they are imported.

Perhaps I shouldn't have "abstracted" my example so much as to sidetrack the
reader's minds.  In fact I was doing

from AAA import aaa
from BBB.AAA import aaa

but the first statement does the wrong thing in the directory python/BBB
because it imports from the file python/BBB/AAA.py instead of the intended
file python/AAA.py.

Huaiyu


>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?  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.  This is even worse on Windows - its file names are caseless - as
>> one has to avoid filenames with different cases as well.
>> 
>> 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!
>> 
>> 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?
>> 
>> In Unix shells, however, this can always be overcome by using absolute
>> paths, like /the/absolute/path/command, whatever the PATH is.
>> 
>> 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 *
>> 
>> This guarantees that module names within packages are well separated.  One
>> can still use
>> from AAA import *
>> to import from any module named AAA that happens to be in the path. IMHO,
>> this would not break any existing code (unless it happens to contain the new
>> keyword 'rootpath').  It would certainly facilitate much easier use of
>> packages. The only real problem I can see of is that developers might (for
>> what reason?) rush to occupy real estates under rootpath.  But since the
>> standard distribution is centrally controlled and add-ons are user
>> controlled, this shouldn't be a big problem.
>> 
>> --
>> Huaiyu Zhu                       hzhu at users.sourceforge.net
>> Matrix for Python Project        http://MatPy.sourceforge.net
>> --
>> http://www.python.org/mailman/listinfo/python-list
>


-- 
Huaiyu Zhu                               hzhu at knowledgetrack.com
KnowledgeTrack Corporation               Tel: 925 738 1907
7020 Koll Center Parkway, Suite 110      Fax: 925 738 1039
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Huaiyu Zhu                       hzhu at users.sourceforge.net
Matrix for Python Project        http://MatPy.sourceforge.net