Prepare a virtual environment (so it wont mess up existing setup)

sudo easy_install pip
sudo pip install virtualenv virtualenvwrapper
mkdir domains # create a directory to store different virtual environments

Create a temporary text file (say ~/appendthis) with below text

export WORKON_HOME=$HOME/domains
source /usr/local/bin/virtualenvwrapper.sh
export PIP_VIRTUALENV_BASE=$

Append that temp file to ~/.zshenv (or .profile or .bashrc depending on your shell)

cat ~/appendthis >> ~/.zshenv

Exit current shell and start terminal again to see something like this show up:

Linux quant 2.6.32-27-generic #49-Ubuntu SMP Thu Dec 2 00:51:09 UTC 2010 x86_64 GNU/Linux Ubuntu 10.04.1 LTS

Welcome to Ubuntu!
* Documentation:  https://help.ubuntu.com/
Last login: Thu Dec 23 14:35:06 2010 from imac.workgroup
virtualenvwrapper.user_scripts Creating /home/nilesh/domains/initialize
virtualenvwrapper.user_scripts Creating /home/nilesh/domains/premkvirtualenv
virtualenvwrapper.user_scripts Creating /home/nilesh/domains/postmkvirtualenv
virtualenvwrapper.user_scripts Creating /home/nilesh/domains/prermvirtualenv
virtualenvwrapper.user_scripts Creating /home/nilesh/domains/postrmvirtualenv
virtualenvwrapper.user_scripts Creating /home/nilesh/domains/predeactivate
virtualenvwrapper.user_scripts Creating /home/nilesh/domains/postdeactivate
virtualenvwrapper.user_scripts Creating /home/nilesh/domains/preactivate
virtualenvwrapper.user_scripts Creating /home/nilesh/domains/postactivate
virtualenvwrapper.user_scripts Creating /home/nilesh/domains/get_env_details

Now you can create any number of python virtual environments. For example, I create myfirstenv

mkvirtualenv myfirstenv # create my first virtual environment named myfirstenv
pip install BLAH # install BLAH
deactivate # deactivate that virtualenv
rmvirtualenv myfirstenv # remove myfirstenv

To work with virtualenv again, simply type:

workon myfirstenv
cd ~/domains/myfirstenv

Wrappers: Virtualenv provides several useful wrappers that can be used as shortcuts

mkvirtualenv (create a new virtualenv)
rmvirtualenv (remove an existing virtualenv)
workon (change the current virtualenv)
add2virtualenv (add external packages in a .pth file to current virtualenv)
cdsitepackages (cd into the site-packages directory of current virtualenv)
cdvirtualenv (cd into the root of the current virtualenv)
deactivate (deactivate virtualenv, which calls several hooks)

Hooks: One of the coolest things about virtualenvwrapper is the ability to provide hooks when an event occurs. Hook files can be placed in ENV/bin/ and are simply plain-text files with shell commands. virtualenvwrapper provides the following hooks:

postmkvirtualenv
prermvirtualenv
postrmvirtualenv
postactivate
predeactivate
postdeactivate

When you are done with that virtualenv, you can just type

rmvirtualenv myfirstenv # this will destroy that virtualenv named `myfirstenv` under ~/domains