import RPi.GPIO as GPIO
import time

RED_LED = 17
GREEN_LED = 27

GPIO.setmode(GPIO.BCM)
GPIO.setup(RED_LED, GPIO.OUT)
GPIO.setup(GREEN_LED, GPIO.OUT)

try:
    while True:
        # 1. Red ON, Green OFF
        GPIO.output(RED_LED, GPIO.HIGH)
        GPIO.output(GREEN_LED, GPIO.LOW)
        time.sleep(2)

        # 2. Red OFF, Green ON
        GPIO.output(RED_LED, GPIO.LOW)
        GPIO.output(GREEN_LED, GPIO.HIGH)
        time.sleep(2)

        # 3. Both ON
        GPIO.output(RED_LED, GPIO.HIGH)
        GPIO.output(GREEN_LED, GPIO.HIGH)
        time.sleep(2)

        # 4. Both OFF
        GPIO.output(RED_LED, GPIO.LOW)
        GPIO.output(GREEN_LED, GPIO.LOW)
        time.sleep(2)

except KeyboardInterrupt:
    pass

finally:
    GPIO.cleanup()