led.py

import RPi.GPIO as GPIO
import time

print GPIO.VERSION

#set up GPIO using BOARD numbering
GPIO.setmode(GPIO.BOARD)
GPIO.setup(12, GPIO.OUT)
GPIO.setup(16, GPIO.OUT)
GPIO.setup(18, GPIO.OUT)

try:
    while True:

	# light 12
    	GPIO.output(12, GPIO.HIGH)
    	time.sleep(0.2)
    	# off 12
    	GPIO.output(12, GPIO.LOW)

    	# light 16
    	GPIO.output(16, GPIO.HIGH)
    	time.sleep(0.2)
    	# off 16
    	GPIO.output(16, GPIO.LOW)

    	# light 18
    	GPIO.output(18, GPIO.HIGH)
    	time.sleep(0.2)
    	# off 18
    	GPIO.output(18, GPIO.LOW)

except KeyboardInterrupt:
	pass

# cleanup
GPIO.cleanup()