text: #!/usr/bin/python3
  
  # from: http://razzpisampler.oreilly.com/ch07.html
  
  import RPi.GPIO as GPIO
  import time
  
  GPIO.setmode(GPIO.BCM)
  
  GPIO.setup(21, GPIO.IN, pull_up_down=GPIO.PUD_UP) # or try 16
  
  while True:
      input_state = GPIO.input(21)
      if input_state == False:
          print('Button Pressed')
          time.sleep(0.2)
  