# Import necessary modules
from machine import Pin       # To control GPIO pins
from time import sleep        # To create delays

# Step 1: Initialize the LED pins as output
# Create a Pin object for each LED and set it to OUTPUT mode
green_led = Pin(17, Pin.OUT)   # Green LED connected to GPIO 17
yellow_led = Pin(18, Pin.OUT)  # Yellow LED connected to GPIO 18
red_led = Pin(19, Pin.OUT)     # Red LED connected to GPIO 19

# Step 2: Define a function to blink a single LED
def blink_led(led, duration=3):
    led.on()              # Turn the LED ON
    sleep(duration)       # Wait for the specified duration (default 3 seconds)
    led.off()             # Turn the LED OFF
    sleep(0.5)            # Short delay before the next action (optional)

# Step 3: Use an infinite loop to blink each LED one by one
while True:
    print("Green LED ON")       # Print message for debugging or monitoring
    blink_led(green_led)        # Blink the green LED

    print("Yellow LED ON")      # Print message for debugging
    blink_led(yellow_led)       # Blink the yellow LED

    print("Red LED ON")         # Print message for debugging
    blink_led(red_led)          # Blink the red LED