backlight up/down on samsung R428

backlight.py

import sys
import os

class backlight():
    def __init__(self, cmd):
	self.path = "echo '%s' > /sys/class/backlight/samsung/brightness"
	self.limit_down, self.limit_up = 1, 7
	self.current = int(os.popen("cat /sys/class/backlight/samsung/brightness").read().strip())
	self.cmd = cmd.strip()
	self.setbacklight()

    def setbacklight(self):
	if self.cmd == 'up':
	    new_value = self.current + 1
	    if new_value <= self.limit_up:
		os.popen(self.path % new_value).read()
		print 'up to level: ' + str(new_value)
		self.current = new_value
	elif self.cmd == 'down':
	    new_value = self.current - 1
	    if new_value >= self.limit_down:
		os.popen(self.path % new_value)
		print 'down to level: ' + str(new_value)
		self.current = new_value

try:
    cmd = sys.argv[1]
    backlight(cmd)
except IndexError:
    print '''use: 'backlight up' or 'backlight down' '''