virtualenv.txt

First create a directory for your new shiny isolated environment

mkdir ~/virtualenvironment

To create a folder for your new app that includes a clean copy of Python,
simply run:

virtualenv ~/virtualenvironment/my_new_app

(add --no-site-packages if you want to isolate your environment from the main site
packages directory)

To begin working with your project, you have to cd into your directory (project)
and activate the virtual environment.

cd ~/virtualenvironment/my_new_app/bin

Lastly, activate your environment:

source activate

Notice how the prompt of your shell changed to show the active environment. 

That is how you can see that you're in your new environment.

Any packages you install now using pip or easy_install get installed into
my_new_app/lib/python2.7/site-packages.

To exit your virtualenv just type “deactivate”.