Get/Set brightness macOS 10.13+

brightness.py

#!/usr/bin/python

from ctypes import CDLL, c_int, c_double
from Quartz import CGMainDisplayID

main_display_id = CGMainDisplayID()

CoreDisplay = CDLL("/System/Library/Frameworks/CoreDisplay.framework/CoreDisplay")
CoreDisplay.CoreDisplay_Display_SetUserBrightness.argtypes = [c_int, c_double]
CoreDisplay.CoreDisplay_Display_GetUserBrightness.argtypes = [c_int]
CoreDisplay.CoreDisplay_Display_GetUserBrightness.restype = c_double


def set_brightness(disp_id, value):
    brightness /= 100
    return CoreDisplay.CoreDisplay_Display_SetUserBrightness(disp_id, brightness)


def get_brightness(disp_id):
    value = CoreDisplay.CoreDisplay_Display_GetUserBrightness(disp_id)
    return round(value * 100, 2)

print(get_brightness(main_display_id))