Script to set monitor brightness on laptop + all external screens

set-displays-brightness.py

#!/usr/bin/env python
import sys
import os
import re
SCRIPT_NAME = os.path.basename(__file__)

def help():
    print(f"Usage: {SCRIPT_NAME} <brightness>")
    sys.exit(4)

def run_command(cmd, read_lines=False):
    print(f"Running: {cmd}")
    stream = os.popen(cmd)

    if read_lines:
        return stream.read_lines()

    return stream.read()

def get_ddc_displays_indices():
    pattern = re.compile(r'Display (\d)')
    output = run_command("ddcutil detect --nousb --async")

    displays = []
    for m in re.finditer(pattern, output):
        displays.append(int(m.group(1)))

    return displays

def set_laptop_display_brightness(brightness):
    # Monitor laptop screen, is intel, we can use xbacklight
    run_command(f"xbacklight -set {brightness}")

def set_ddc_display_brightness(display_index, brightness):
    # For the rest we use ddc https://www.ddcutil.com/
    run_command(f"ddcutil --display {display_index} setvcp 10 {brightness}")


# https://wiki.archlinux.org/index.php/Backlight
if __name__ == "__main__":
    if len(sys.argv) <= 1:
        help()

    brightness = int(sys.argv[1])

    # Laptop
    set_laptop_display_brightness(brightness)

    # External
    displays = get_ddc_displays_indices()
    for d in displays:
        set_ddc_display_brightness(d, brightness)