I’ve mentioned this before but deleted it because it threw a wrench into things. However, I found a well written how-to for crontab and therefore bringing it up again.
First off the guide is available here: http://www.raspberrypi-spy.co.uk/2013/07/running-a-python-script-at-boot-using-cron/
Second, this method is dead simple once you know how crontab works, I believe crontab is installed by default, sciprts are run late enough in the boot sequence to execute without conflict, etc. To recap the link all you do is:
sudo crontab -e
Add the following line:
@reboot python /home/pi/OSPi/ospi.py &