The main program entry point

At the end of the source file, we have the following code:

# Main entry point
if __name__ == '__main__':
    signal.signal(signal.SIGINT, signal_handler) # Capture CTRL + C
    print_instructions()                              # (18)

    # Initialize LED from last dweet.
    latest_dweet = get_latest_dweet()                 # (19)
    if (latest_dweet):
        process_dweet(latest_dweet)

    print('Waiting for dweets. Press Control+C to exit.')

    #Only use one of the following.
    #stream_dweets_forever() # Stream dweets real-time.                     
    poll_dweets_forever() # Get dweets by polling.    # (20)

On line (8), print_instructions()  is responsible for printing the sweet URLs to the Terminal, while on line (19), we see a call to get_latest_dweet(). This call initializes our LED to the last dweeted state when the program starts. Finally, on line (20), we start polling the dweet.io service to access the latest dweets...