Assumptions: you are running Rasbian
You have a couple different options. For testing, you can run
nohup ./python_script.py &. That uses a program called nohup to redirect all console output to a file, and then give you back your terminal.
Long term, you will probably want to start the program with cron and run it on reboot, so if the power goes out out your program will start as soon as it boots back up.
Cron is a little more advanced and requires a little more thought to setup. You have options as far as running a program at a certain time. For your application, it sounds like you can do something as simple as
$ crontab -e
and add the line:
Save and close, and then run
# update-rc.d cron defaults