Including global package into a virtualenv that has been created with --no-site-packages

If you're using virtualenvwrapper and you might be able to use the postmkvirtualenv script to automatically create symlinks in the new virtualenv sitepackages directory.

#!/bin/sh
cdsitepackages
ln -s /path/to/system/site-packages/package-name
cdvirtualenv

If you are using virtualenvwrapper, the shell command add2virtualenv should be present in an active virtualenv. Use:

add2virtualenv /path/to/package

to add an entry to the PTH file _virtualenv_path_extensions.pth in your virtualenv site-packages.

The benefit of using add2virtualenv rather than creating symlinks yourself, is that you can remove the package from being importable by commenting out its line in the PTH file. This makes it easier to check your code's validity against several versions of a library on which it depends.