Linux/Win32 func. to get Python instdir (not exedir) + site-packages => extensions mgmt

[Diez B. Roggisch]

> 
> Diez,
> 
> I repeat I am a newbie, so please don't be angry against me, if I say
> something stupid or if I propose a method not efficient.

Where did I sound angry? 
 
> An easy way to get the absolute path of site-packages seems very
> useful to me, in order to check anything (all extensions available and
> not provided by sys.path, etc.) related to the files on the
> filesystem, if necessary.

As I said - this is a wrong assumption. The whole purpose of the sys.path is
to specify locations where modules/packages are installed. Note the plural.

And matter of factly (as I told you in the last post already), this happens
in e.g. debian based distributions install certain packages
under /usr/share, which is by no means a prefix of /usr/python2.5 where the
site-packages are.

So if you want to find out if something is already installed, you need to
consider ALL the contents of sys.path.

Besides, I don't understand why you want to do it that way anyway. If you
need a certain package,  do

try:
  import package
except ImportError:
  do_install_package()

This should/could be part of your installer script (most probably setup.py)

And have you heard of setuptools? They do actually manage and install
pytthon packages with dependencies. Before reinventing another wheel...

> For the automatic installation of missing extensions (using admin
> rights), I think that it is not difficult to do it on both
> platforms...

You are underestimating that task. It is, on both platforms. There are many
discussions about this, why some people don't like setuptools because it
works with python as center of it's perspective whereas linux often has
package management for the whole system.

I suggest you start acquainting yourself with setuptools and how and what
they did to essentially solve what you seem to be wanting. And try and see
if that's not a route you can go - just using setuptools.

Diez