Blinking LEDs on IO-Pins

led.py

import time
import RPi.GPIO as GPIO

try:
    # Set Mode to BCM
    GPIO.setmode(GPIO.BOARD)

    # Define output LEDs
    GPIO.setup(11, GPIO.OUT, initial=GPIO.LOW)
    GPIO.setup(13, GPIO.OUT, initial=GPIO.LOW)
    GPIO.setup(15, GPIO.OUT, initial=GPIO.LOW)
    GPIO.setup(16, GPIO.OUT, initial=GPIO.LOW)

    while True:
        # Activate all LEDs
        GPIO.output(11, GPIO.HIGH)
        GPIO.output(13, GPIO.HIGH)
        GPIO.output(15, GPIO.HIGH)
        GPIO.output(16, GPIO.HIGH)

        print "An"

        # Wait
        time.sleep(0.5)

        # Deactivate all LEDs
        GPIO.output(11, GPIO.LOW)
        GPIO.output(13, GPIO.LOW)
        GPIO.output(15, GPIO.LOW)
        GPIO.output(16, GPIO.LOW)

        print "Aus"

        # Wait
        time.sleep(0.5)
finally:
    GPIO.cleanup()