import statement - package visibility problem

[Laszlo Zsolt Nagy]

  Hi All!

I have the following structure:


/Lib/Server/Db/
    __init_.py
    DatabaseConnection.py
    Adapters/
       __init__.py
       FireBirdConnection.py

Important file contents are:

/Lib/Server/Db/__init__.py:

    import DatabaseConnection
    import Adapters

/Lib/Server/Db/DatabaseConnection.py:

    class DatabaseConnection(object):
          pass


/Lib/Server/Db/Adapters/__init__.py

    import FireBirdConnection

/Lib/Server/Db/Adapters/FireBirdConnection.py:

    from DatabaseConnection import DatabaseConnection
    class FireBirdConnection(DatabaseConnection):
           pass

Here is the problem. I go to the directory where 'Lib' resides. Then I do:

C:\Temp\ccc>python
Python 2.4.1 (#65, Mar 30 2005, 09:13:57) [MSC v.1310 32 bit (Intel)] on 
win32
Type "help", "copyright", "credits" or "license" for more information.
 >>> import Lib
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "Lib\__init__.py", line 1, in ?
    import Server
  File "Lib\Server\__init__.py", line 1, in ?
    import Db
  File "C:\Python\Lib\Db\__init__.py", line 29, in ?
    import      Adapters
  File "C:\Python\Lib\Db\Adapters\__init__.py", line 21, in ?
    import FireBirdConnection
  File "Db\Adapters\FireBirdConnection.py", line 27, in ?
ImportError: No module named DatabaseConnection
 >>>

My problem is that Lib/Server/Db/Adapters/FireBirdConnection.py does not 
see Lib/Server/Db/DatabaseConnection.py.
Of course I read the documentation about the import statement but I do 
not see a good solution.

Possible solutions and their drawbacks:

Solution 1:

Put the 'Db' directory into my PYTHONPATH or append it to "sys.path". It 
is too bad. This could make my 'Db' module
visible but this is not a good solution. For example, I can have this 
module structure:

Lib/
    Client/
       Db/
          Adapters/
    Server/
       Db/
          Adapters/

E.g. there could be two "Db" modules, one for Client and one for Server. 
Clearly, I cannot add EVERY module path to sys.path. It would be 
ambiguous to import 'Adapters', for example.

Solution 2:

Add the outermost 'Lib' directory to sys.path and use fully qualified 
module names.  In the example above I could use this:

/Lib/Server/Db/Adapters/FireBirdConnection.py:

    from Lib.Server.Db.Adapters.DatabaseConnection import DatabaseConnection

In this case FireBirdConnection.py would be dependent on the full module 
path. Otherwise it is independent on the whole module path, it only 
depends on the 'upper level' module, regardless of its name. So here are 
the problems with this solution:


- What if I want to rename 'Server' to 'Middletire'? Should I change all 
of my files inside the 'Midletire' dir?
-What if I would like to unify the server and client Db sides? Should I 
rename "from Lib.Server.Db.Adapters.DatabaseConnection import 
DatabaseConnection" to "from Lib.Db.Adapters.DatabaseConnection import 
DatabaseConnection" in all files?
- Lastly, the import statements are too long.  They are hard to manage.

I would like to use something like

    from __uppermodule__.DatabaseConnection import DatabaseConnection

but probably there is a standard Pythoninc way to do it. Just I can't 
find it.
Maybe we can start a new PEP on this. :-)

Please advise.

p.s.: sorry for the long e-mail

-- 
_________________________________________________________________
  Laszlo Nagy		      web: http://designasign.biz
  IT Consultant		      mail: gandalf at geochemsource.com

     		Python forever!