can python access OS level features like bash scripting?

[Krishnakant]

Hello all,
Right now I am a bit confused on a final stage of my project.

I need to create an installer and an executable file for my python
program for gnu/linux.

The install script has to put the package into site-packages folder
where all other libraries reside.  Then put the executable file
into /usr/bin as other files.

The installer must also do the basic task of creating the database and
setting up password for on postgresql.
now here comes the main problem.
I believe putting files into proper places is pritty easy (may be some
one will instantly reply to the issue of putting the executable file and
libraries in place ).  But to do the database based activities, I need
python-psycopg2 module for postgresql in the first place.  So is it
possible for python to self download and install all the necessary
modules on to the client machine?

What further complicates the system is the fact that I want in future to
create 2 deb files, one for installing the gtk based client application
and the other to install the server side app made in python-twisted for
rpc.  Now the obvious problem is that first my python installation
(either 2.5 or 2.4) must check for itself if the modules are present or
not and if they are not present, my install utility must either download
it from net or if that's not the recommended approach then compile the
module from the source.

how do I achieve all this in python?
I know bash could be used to do such things but I don't want to use bash
because it is to clunky and won't run easily on windows.
Moreover I want to create a deb file as I said before so I want to keep
it as simple as possible.

Even regarding the executable, I am confused on using bash as the script
for writing the executable which can then do some thing like python -c
and call the modules, or write this executable code in a main.py and put
that file into the executable path i.e /usr/bin.

Please clear this mater so that I can go ahead.

I know the python list is pritty busy and I must thank all the members
who keep the spirit of the community and the professional organisations
alive so may be I will get a solution to my problem soon.

happy hacking.
Krishnakant.