oh-my-zsh/plugins/autoenv/autoenv.plugin.zsh

# Activates autoenv or reports its failure
if ! source $HOME/.autoenv/activate.sh 2>/dev/null; then
  echo '-------- AUTOENV ---------'
  echo 'Could not find ~/.autoenv/activate.sh.'
  echo 'Please check if autoenv is correctly installed.'
  echo 'In the meantime the autoenv plugin is DISABLED.'
  echo '--------------------------'
  return 1
fi

# The use_env call below is a reusable command to activate/create a new Python
# virtualenv, requiring only a single declarative line of code in your .env files.
# It only performs an action if the requested virtualenv is not the current one.

use_env() {
    typeset venv
    venv="$1"
    if [[ "${VIRTUAL_ENV:t}" != "$venv" ]]; then
        if workon | grep -q "$venv"; then
            workon "$venv"
        else
            echo -n "Create virtualenv $venv now? (Yn) "
            read answer
            if [[ "$answer" == "Y" ]]; then
                mkvirtualenv "$venv"
            fi
        fi
    fi
}