I have a flask application which I am currently starting up in the following way:
#phantom.py __author__ = \'uruddarraju\' from phantom.api.v1 import app app.run
$ python phantom.py &
Is probably the easiest way to make it run in the background. That said you should not be using the app.run() server to serve your flask app if you are moving it into production as @LukasGraf mentions (as well as I believe their documentation)