nixpkgs/pkgs/development/interpreters/python/2.7/setup-hook.sh

addPythonPath() {
    addToSearchPathWithCustomDelimiter : PYTHONPATH $1/lib/python2.7/site-packages
}

toPythonPath() {
    local paths="$1"
    local result=
    for i in $paths; do
        p="$i/lib/python2.7/site-packages"
        result="${result}${result:+:}$p"
    done
    echo $result
}

envHooks+=(addPythonPath)