#!/usr/bin/python
import RPi.GPIO as GPIO
import time
x = "50"

GPIO.setmode(GPIO.BCM)
GPIO.setup(21, GPIO.OUT)

# time to sleep between operations in the main loop

# main loop
while x == "50":
  time.sleep(1)
  GPIO.output(21, GPIO.HIGH)
  print("on")
  time.sleep(1)
  GPIO.output(21, GPIO.LOW)
  print("off")
# Reset GPIO settings
GPIO.cleanup()

# find more information on this script at
# http://youtu.be/oaf_zQcrg7g