You could try to rely on clear but it might not be available on all Linux distributions. On windows use cls as you mentionned.
import subprocess
import platform
def clear():
subprocess.Popen( "cls" if platform.system() == "Windows" else "clear", shell=True)
clear()
Note: It could be considered bad form to take control of the terminal screen. Are you considering using an option? It would probably be better to let the user decide if he want to clear the screen.