Automatic virtualenv switching for virtualenvwrapper

virtualenvwrapper_autoswitch.sh

# Automatic activation and deactivation of virtualenvs using virtualenvwrapper
# whereby the virtualenv name must match the current directory name
function cd
{
  # Perform the regular cd
  builtin cd "$@"

  # Iterate through the current directory, heading into each parent directory
  # until we find a .virtualenv file or land in the top directory (/)
  test_directory=$(pwd)
  while [ "$test_directory" != "/" ]
  do
    # The .virtualenv definition was found
    if [ -f $test_directory/.virtualenv ]
    then
      virtualenv=$(cat $test_directory/.virtualenv)

      # The virtualenv is not yet activated
      if [ -z $VIRTUAL_ENV ] || [ $VIRTUAL_ENV != $WORKON_HOME/$virtualenv ]
      then
        if [ -f $WORKON_HOME/$virtualenv/bin/activate ]
        then
          source $WORKON_HOME/$virtualenv/bin/activate
        else
          echo "The virtualenv $virtualenv doesn't exist, unable to activate"
        fi
      fi
      break
    else
      test_directory=$(dirname "$test_directory")
    fi
  done

  # If no virtualenv was found and one is already activated, we deactivate
  # it for the user
  if [ "$test_directory" == "/" ] && [ ! -z $VIRTUAL_ENV ] && \
     [[ $VIRTUAL_ENV == $WORKON_HOME/* ]]
  then
    deactivate
  fi
}