setup.py when you can't write to site-packages?

[andybak]

There are several gaps in my Python knowledge, one of which is the what
exactly setuptools does and how it works.

I'm on a shared host so can't write to site-packages therefore most
setup.py's fail.

My strategy for pure python packages is to run setup.py locally and
copy anything that gets put in site-packages across to the shared host
somewhere in my Python path. I'm sure there is a better solution!

What's the best approach for situations when you can't tamper with the
Python install?