import RPi.GPIO as GPIO
import time

led = 23

GPIO.setwarnings(False)
GPIO.setmode(GPIO.BCM)
GPIO.setup(led,GPIO.OUT)

print "CTRL+C = STOP program"

try:
    while True:
        GPIO.output(led,GPIO.HIGH)               
        time.sleep(0.5)
        GPIO.output(led,GPIO.LOW)         
        time.sleep(0.5)
except KeyboardInterrupt:
    GPIO.cleanup()  # must be executed before program stop