virtualenv is a tool that creates sandboxed Python environments.
virtualenv allows you to create a sandboxed and isolated environment where Python packages can be installed without interfering with other packages on the same machine. With several virtualenvs, many different pieces of Python software with different and even mutually exclusive dependencies can live together.
The source code of this tool is hosted on GitHub.
Basic usage:
$ virtualenv ENV
$ source ENV/bin/activate
(ENV) $ easy_install (package)
(ENV) $ deactivate
$ ...
See the Command reference for a complete list of all available commands.