A lot of ways. Offhand:
1. The easiest:
python skriptu &
2. In screen
-session. Start screen. To run the script. Out of session.
A bonus for the number of the session you can go to this screen at any time and watch the status of the script execution.
3. To write a script, for example something like this: https://gist.github.com/naholyr/4275302
to start as a service. Bonus you can set the autostart at startup of the OS.
4. To write a python script daemon, for example something like this: https://github.com/serverdensity/python-daemon/blo...
If you want to start a process from a Python script, which will continue to live after the completion of the Python script, you need to use os.fork()