import RPi.GPIO as GPIO 
import time 
PIN_NO=12; 
GPIO.setmode(GPIO.BOARD) 
GPIO.setup(PIN_NO, GPIO.OUT) 
for x in xrange(500):
	GPIO.output(PIN_NO,GPIO.HIGH) 
	time.sleep(2)
	GPIO.output(PIN_NO,GPIO.LOW ) 
	time.sleep(2) 
GPIO.cleanup()