Script to use with optirun-desktop.nemo_action. Must be stored in the same folder as the nemo_action file (~/.local/share/nemo/actions) and be set to executable.

optirun-desktop.py

#! /usr/bin/python -OOt

import sys
import os
from gi.repository import GLib

path = sys.argv[1]

GROUP = "Desktop Entry"

keyfile = GLib.KeyFile.new()

if keyfile.load_from_file(path, GLib.KeyFileFlags.NONE):
    if keyfile.has_group(GROUP):
        try:
            cmd = keyfile.get_string(GROUP, "Exec")
            os.system("optirun %s" % cmd)
        except GLib.GError:
            pass