on a clean mac
sudo easy_install pip
sudo pip install virtualenv
USAGE
Let’s say you have a directory called myproject. Setup virtualenv for that project.
$ cd myproject
$ virtualenv venv
If you want your virtualenv to also inherit globally installed packages (like iPhython or Numpy) run:
$ virtualenv venv –system-site-packages
Once venv subdirectory is created you need to activate it.
$ source venv/bin/activate
You should see (venv) appear at the start of your terminal prompt
you can now install packages
$ pip install <package>
to leave virtual env
$ deactivate