zsh: auto-enter python virtualenvs on cd

.zshrc

#
#  python: enter virtualenv on chpwd
#
load-py-venv() {
    if [ -f .venv/bin/activate ]; then
        # enter a virtual environment that's here
        source .venv/bin/activate
    elif [ -f env/bin/activate ]; then
        source env/bin/activate
    elif [ ! -z "$VIRTUAL_ENV" ] && [ -f pyproject.toml -o -f requirements.txt ]; then
        # exit a virtual environment when you enter a new project folder
        deactivate
    fi
}
add-zsh-hook chpwd load-py-venv
load-py-venv