A snippet to automatically call virtualenvwrapper's "workon" command when entering a directory in the shell. This can be added to your .profile, .bash_profile, .bashrc, etc.

.bashrc

# Call virtualenvwrapper's "workon" if .venv exists.  This is modified from--
# http://justinlilly.com/python/virtualenv_wrapper_helper.html
# which is linked from--
# http://virtualenvwrapper.readthedocs.org/en/latest/tips.html#automatically-run-workon-when-entering-a-directory
check_virtualenv() {
    if [ -e .venv ]; then
        env=`cat .venv`
        echo "Found .venv in directory. Calling: workon ${env}"
        workon $env
    fi
}
venv_cd () {
    builtin cd "$@" && check_virtualenv
}
# Call check_virtualenv in case opening directly into a directory (e.g
# when opening a new tab in Terminal.app).
check_virtualenv

# Add the following to ~/.bash_aliases:
# alias cd="venv_cd"