how can i control same natron project via cmd without being open it again

import os
import NatronEngine
from NatronGui import *

index = 0
app = natron.getInstance(index)

background = app.createReader(“F:/RavenEffects/background.mp4”)
greenscreen = app.createReader(“F:/RavenEffects/greenscreen.jpg”)
chromakeyer = app.createNode(“net.sf.openfx.ChromaKeyerPlugin”)
chromakeyer.connectInput(3,background)
viewer=app.createNode(“fr.inria.built-in.Viewer”)
viewer.connectInput(0,chromakeyer)

guys , i need to execute above code step by step via cmd.
but when i run .py file with only one line in it, natron is open again.
i just need to control opened project with seperate commands.
plz help me.