Virtualenv is a tool to create isolated Python environments. For the detail reasons of using it, please refer to ​https://virtualenv.pypa.io/en/latest/ .

Docs and Development of Virtualenv:

Docs: ​http://www.virtualenv.org/

Development: ​https://github.com/pypa/virtualenv

There is also virtualenvwrapper that extends virtualenv to make it easier to work with multiple virtualenvs:

Docs: ​http://www.doughellmann.com/projects/virtualenvwrapper/

Development: ​https://bitbucket.org/dhellmann/virtualenvwrapper