def song_info(artist_name, song_title, release_date = None):        # We give no value to 'release_date'. 'None' is a placeholder
    """Build a dictionary containing information about an album."""
    song_dict = {'artist': artist_name, 'song': song_title} # We add the two arguments provided to the dictionary
    if release_date:                                         # If there is an argument provided for 'release_date' then execute this block.
        song_dict['released'] = release_date                # Add the release date to the dictionary.
    return song_dict



# Prepare the prompts.
song_prompt = "Which song are you thinking of? "
artist_prompt = "Who's the artist? "
released_prompt = "When was it released? "

while True:
    released = None                                          # We give the 'release' no value so if the user does not provide input for this variable python wont cause
                                                             # any problems
    print("nEnter 'quit' at any time to stop.")

    song = input(song_prompt)
    if song == 'quit':
        break
    artist = input(artist_prompt)
    if artist == 'quit':
        break

    release_question = input("Do you know when it was released?(yes/no) ")  # Ask the use if they know the release date.
    if release_question == 'yes':                                           # If they know execute this block.
        released = input(released_prompt)                               # Ask the user for the release date.

        if released == 'quit':
            break

    elif release_question == 'quit':
        break


    song_info = song_info(artist, song, released)
    print(song_info)