pyDictionaryExample

# Demonstration script for handling a Dictionary in Python, used as a mini database
# Mike Kerry - Jan 2021 - acclivity2@gmail.com

# This dictionary will be indexed by Musical Artist
# Each Artist entry will hold a list of Albums by that artist
# Album data will include Date of Release and the medium (e.g. EP/LP/CD/MP3/Video)

# Example format of the Dictionary
# {'BEATLES': ['Beatles', ['ABBEY ROAD', 'Abbey Road', '1969', 'CD'], ['LET IT BE', 'Let It Be', '1970', 'CD'], ['HELP', 'Help', '1965', 'LP']],
# 'WHO': ['Who', ['MY GENERATION', 'My Generation', '1965', 'CD'], ['WHO', 'Who', '2019', 'CD']],
# 'FRANK SINATRA': ['Frank Sinatra', ['MY WAY', 'My way', '1969', 'LP']]}

# The dictionary data will be backed up in a CSV file, with one line per album
# Beatles,Abbey Road,1969,CD
# Beatles,Let It Be,1970,CD
# Beatles,Help,1965,LP
# Who,My Generation,1965,CD
# Who,Who,2019,CD
# Frank Sinatra,My way,1969,LP


def normalise_artist(p_artist):
    # This routine can be used if required, to remove "The " off the front of an Artist name
    # Then, for example, "The Beatles" and "Beatles" are treated as the same group
    p_artist = p_artist.title()
    if p_artist.upper()[:4] == "THE ":
        return p_artist[4:]
    return p_artist


def add_artist(p_artist):
    global music_dict

    # We will make the Artist Key all upper-case to avoid case discrepancies on look-up
    p_artist_key = p_artist.upper()

    if p_artist_key not in music_dict:
        # Create a new entry. For now it only contains the original form of the artist name
        music_dict[p_artist_key] = [p_artist]
        return True
    else:
        return False            # Return False to say add was not possible


def add_album(p_artist, p_album, p_date, p_medium):
    global music_dict

    # Make the album key all upper case
    p_artist_key = p_artist.upper()
    p_album_key = p_album.upper()
    t_artist_data = music_dict[p_artist_key]
    # The above statement extracts all the data held for one artist into a list named t_artist_data
    # This list holds the original artist name, followed by a sub-list with  one entry per album
    # Example: ['Who', ['MY GENERATION', 'My Generation', '1965', 'CD'], ['WHO', 'Who', '2019', 'CD']]
    # Existing albums are elements 1 upwards within the artist data
    for t_idx in range(1, len(t_artist_data)):
        t_alist = t_artist_data[t_idx]
        if t_alist[0] == p_album_key:       # Does the album name we want to add already exist?
            return False                    # - yes - return saying add failed
    t_artist_data += [[p_album_key, p_album, p_date, p_medium]]     # append a new sub-list to the artist data
    music_dict[p_artist_key] = t_artist_data    # insert the extended data back into the database for this artist
    return True                             # Return a flag saying album was added successfully


music_dict = {}

# Read text file (CSV format) and build Dictionary

fin = open("MusicData.txt")
for lina in fin:
    lina = lina.strip()
    splita = lina.split(",")
    if len(splita) < 3:
        continue                # Ignore incomplete lines
    for x, el in enumerate(splita):
        splita[x] = el.strip()

    # Extract the parts from one album line
    artist = splita[0].title()
    artist = normalise_artist(artist)
    album = splita[1]
    date = splita[2]
    medium = splita[3]
    print(artist, album, date, medium)

    # Add this album to our dictionary
    add_artist(artist)
    add_album(artist, album, date, medium)


fin.close()
print(music_dict)

while True:
    print("1. Add new artist")
    print("2. Add new album")
    print("3. List albums for an artist")
    print("4. Find album")
    print("9. Quit")
    option = input("Choose an option: ")
    if option == "1":
        # New artist
        artist = input("Enter Artist name: ")
        artist = normalise_artist(artist)
        res = add_artist(artist)
        if res is False:
            print("That artist is already in the database")
        else:
            print("Artist", artist, "added to database")

        continue

    if option == "2":
        artist = input("Enter Artist for this album: ")
        artist = normalise_artist(artist)
        artist_key = artist.upper()
        if artist_key not in music_dict:
            print("That artist is not in the database")
            continue
        album = input("Enter Album Name: ")
        album_key = album.upper()
        date = input("Enter Release Date: ")
        medium = input("Enter Medium (EP/LP/CD: ")

        res = add_album(artist, album, date, medium)

        if res is False:
            print("That album is already in the database")
        else:
            print("Album has been added")

        continue

    if option == "3":
        artist = input("Enter Artist Name: ")
        artist = normalise_artist(artist)
        artist_key = artist.upper()
        if artist_key not in music_dict:
            print("That artist is not in the database")
            continue
        # List albums for the artist
        artist_data = music_dict[artist_key]
        # artist_data contains original artist name + a list of lists of albums
        # Existing albums are elements 1 upwards within the artist data
        for idx in range(1, len(artist_data)):
            alist = artist_data[idx]
            album = alist[1]
            date = alist[2]
            medium = alist[3]
            print(artist.ljust(15), album.ljust(20), date.ljust(8), medium.ljust(6))

    if option == "4":
        # Search all Artists for an Album name
        album = input("Enter Album Name: ")
        album_key = album.upper()
        found = False
        for artist_key in music_dict.keys():
            artist_data = music_dict[artist_key]
            for x in range(1, len(artist_data)):
                album_data = artist_data[x]
                if album_data[0] == album_key:
                    found = True
                    artist = artist_data[0]
                    album = album_data[1]
                    date = album_data[2]
                    medium = album_data[3]
                    print(artist.ljust(15), album.ljust(20), date.ljust(8), medium.ljust(6))

        if not found:
            print("No album named", album, "was found")

    if option == "9":
        # Quit. Write the dictionary back out to the text file in CSV format
        fout = open("MusicData.txt", 'w')
        for artist_key in music_dict.keys():
            artist_data = music_dict[artist_key]
            artist = artist_data[0]
            for x in range(1, len(artist_data)):
                album_data = artist_data[x]
                album = album_data[1]
                date = album_data[2]
                medium = album_data[3]
                outline = ",".join([artist, album, date, medium]) + "\n"
                fout.write(outline)
        fout.close()
        break               # Quit