Do these first:

• Install Python 2 and/or 3

  # On Mac >= 10.5 with homebrew
  $ brew update
  ## Install Python 2
  $ brew install python
  ## Install Python 3
  $ brew install python3
  ## Follow any instructions that appear after each brew install
  

  # Is everything working?
  $ brew doctor
  # Listen to the doctor
  

  # Run Python 2
  $ python
  # Run Python 3
  $ python3
  # Install a Python 2 package
  $ pip install some-package
  # Install a Python 3 package
  $ pip3 install some-package
  

   [full instructions]

Install the packages.

$ pip install virtualenv
$ pip install virtualenvwrapper

Open your shell's profile config (e.g. .bash_profile, .bashrc, or .zshrc). This is usually located in your home directory.

Then add the following:

# ~/.bash_profile

# Enable virtualenvwrapper 
VIRTUALENVWRAPPER_PYTHON=/usr/local/bin/python
export WORKON_HOME=~/Envs
source /usr/local/bin/virtualenvwrapper.sh

On Window, you can use the virtualenvwrapper-powershell.

# Virtualenvwrapper-powershell in Windows
PS> pip install virtualenvwrapper-powershell
PS> $env:WORKON_HOME="~/Envs"
PS> mkdir $env:WORKON_HOME
PS> import-module virtualenvwrapper

Create the folder for your virtual environments.

# Reload your profile
$ source ~/.bash_profile
# Create your env directory
$ mkdir -p $WORKON_HOME

Now, when you log in to a new shell session, you will be able to use virtualenvwrapper.

# Create a new environment
$ mkvirtualenv my-fresh-environment
# Activate an environment
$ workon my-fresh-environment
# List environments
$ lsvirtualenv
# Remove an environment
$ rmvirtualenv my-polluted-environment

See also:

• Virtual Environments - Hitchhiker's Guide to Python
• Virtualenvwrapper docs
• Virtualenvwrapper-powershell for Windows users