pyChangeBrightness.py

#!/usr/bin/env python

import sys
import subprocess as sp

def get():
	currentLevel = int(float(sp.Popen("xbacklight -get", shell=True, stdout=sp.PIPE, stderr=sp.PIPE).communicate()[0].strip()))
	if sys.argv[1] == "up":
		change(str(currentLevel + 20))
	else:
		change(str(currentLevel - 20))

def given():
	currentLevel = int(float(sys.argv[2]))
	if sys.argv[1] == "up":
		change(str(currentLevel + 20))
	else:
		change(str(currentLevel - 20))

def change(newLevel):
	command = "xbacklight -time 0 -steps 1 -set " + newLevel
	result = sp.Popen(command, shell=True, stdout=sp.PIPE, stderr=sp.PIPE).communicate()[0].strip()
	print result, command


cases = {1 : lambda : sys.exit(0),
	 2 : get,
	 3 : given
	}

cases[len(sys.argv)]()