Use interrupt based GPIO

[bornskilled200]

https://github.com/g0to/misc_scripts/blob/master/raspi_gpio_actions_INT.py

import subprocess
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)

# GPIO3 (pin 5) set up as input. It is pulled up to stop false signals
GPIO.setup(3, GPIO.IN, pull_up_down=GPIO.PUD_UP)

# wait for the pin to be sorted with GND and, if so, halt the system
GPIO.wait_for_edge(3, GPIO.FALLING)
subprocess.call(['shutdown -h now "System halted by GPIO action"'], shell=True)

# clean up GPIO on normal exit
GPIO.cleanup()