Install virtualenv:

    pip install virtualenv
    mkdir ~/.virtualenvs
    virtualenv ~/.virtualenvs/my_new_project

Activate it to continue development:

    . ~/.virtualenvs/my_new_project/bin/activate

The effect of this is that `python` and `pip` commands now only act on the virtualenv and not system (or user) site wide.

Deactivate it:

    deactivate

Python and pip commands are now the system versions again.