#!/usr/bin/env python3
 
import RPi.GPIO as GPIO
import time

def click(self):
    print('event detected')

in_pin = 4
GPIO.setmode(GPIO.BCM)
GPIO.setup(in_pin, GPIO.IN, pull_up_down=GPIO.PUD_UP)
GPIO.add_event_detect(in_pin, GPIO.FALLING, callback=click,
                                  bouncetime=100)

while  True:
    time.sleep(0.2)