<p>I've been using virtualenv lately while developing in python. I like the idea of a segregated development environment using the <strong>--no-site-packages</strong> option, but doing this while developing a PyGTK app can be a bit tricky.
The PyGTK modules are installed on Ubuntu by default, and I would like to make a virtualenv (with --no-site-packages) aware of specific modules that are located elsewhere on the system.</p>
<p>What's the best way to do this? Or should I just suck it up and drop the --no-site-packages option?</p>

One way is to add the paths to your code using sys.path.
```
```
import sys

sys.path.append(somepath)
```
```
Another way is to use site, which processes .pth files in addition to adding to sys.path.
```
```
import site

site.addsitedir(sitedir, known_paths=None)
```
```
https://docs.python.org/library/site.html
But you probably don't want to add this to all your related code.
I've seen mention of sitecustomize.py being used to perform something like this, but after some testing I couldn't get it to work as might be expected.
Here it mentions that auto-import of sitecustomize.py ended in 2.5, if your not on 2.5 try it out.  (just add one of the path add methods above to the file and drop it in the directory your program is run)
A work around method is mentioned in the post for users of 2.5 and up.
http://code.activestate.com/recipes/552729/