Ubuntu / Linux Mint Brightness control. I could not find real fix for problem with keys changing brightness level on my laptop. So wrote little Python 3 script. Add alias to this file in .bashrc

brightness.py

#! /usr/bin/env python3
# -*- coding: utf-8 -*-
# vim:fenc=utf-8
#
# Copyright © 2016 FZX <FZX@users.noreply.github.com>
#
# Distributed under terms of the GPL v2.0 license.

"""
Controlling brightness for nv_backlight.

On my laptop does not work brightness control
with keys. So this little script will help me
to do it manually from terminal.
Make alias to this file in .bashrc
alias br='sudo python3 brightness.py'
"""

import os
import sys

def current_level():
    with open("/sys/class/backlight/nv_backlight/brightness", "r") as f:
        level = f.read()
    return level


def update_level(value):
    with open("/sys/class/backlight/nv_backlight/brightness", "w") as f:
        f.write(str(value))
    print("Brightness level set to {}".format(value))


def get_new_value():
    error_message = "Please use only this format 'br 30'! Max level is 100!"
    try:
        new_value = int(sys.argv[1])
        if (len(sys.argv) > 2) or (new_value > 100):
            print(error_message)
        else:
            return abs(new_value)
    except:
        print(error_message)

def notify(value):
    os.popen("sudo -u mint notify-send -i /usr/share/icons/Mint-X/devices/scalable/computer-symbolic.svg 'Brightness' 'Level set to {}'".
             format(value))

def main():
    if len(sys.argv) < 2:
        print("Current brightness level is:", current_level())
    elif sys.argv[1] == "+":
        if current_level().strip() != "100":
            new_level = int(current_level()) + 10
            update_level(new_level)
            notify(new_level)
    elif sys.argv[1] == "-":
        if current_level().strip() > "10":
            new_level = int(current_level()) - 10
            update_level(new_level)
            notify(new_level)
    else:
        level = get_new_value()
        if level:
            update_level(level)


if __name__ == '__main__':
    main()