请教大神，一小段代码看不明白

def lookup(d, key):
    found = False
    for child in d:
        if found: return child.text
        if child.tag == 'key' and child.text == key:
            found = True
    return None


stuff = ET.parse(fname)
all = stuff.findall('dict/dict/dict')
print('Dict count:', len(all))
for entry in all:
    if (lookup(entry, 'Track ID') is None): continue

    name = lookup(entry, 'Name')
    artist = lookup(entry, 'Artist')
    album = lookup(entry, 'Album')
    genre = lookup(entry, 'Genre')
    count = lookup(entry, 'Play Count')
    rating = lookup(entry, 'Rating')
    length = lookup(entry, 'Total Time')

    if name is None or artist is None or album is None or genre is None:
        continue

    print(name, artist, album, genre, count, rating, length)

    cur.execute('''INSERT OR IGNORE INTO Artist (name) 
        VALUES ( ? )''', (artist,))
    cur.execute('SELECT id FROM Artist WHERE name = ? ', (artist,))
    artist_id = cur.fetchone()[0]

    cur.execute('''INSERT OR IGNORE INTO Album (title, artist_id) 
        VALUES ( ?, ? )''', (album, artist_id))
    cur.execute('SELECT id FROM Album WHERE title = ? ', (album,))
    album_id = cur.fetchone()[0]

    cur.execute('''INSERT OR IGNORE INTO Genre (name) 
        VALUES ( ? )''', (genre,))
    cur.execute('SELECT id FROM Genre WHERE name = ? ', (genre,))
    genre_id = cur.fetchone()[0]

    cur.execute('''INSERT OR REPLACE INTO Track
        (title, album_id, genre_id, len, rating, count) 
        VALUES ( ?, ?, ?, ?, ?, ? )''',
                (name, album_id, genre_id, length, rating, count))

   cur.execute('SELECT id FROM Artist WHERE name = ? ', (artist,))
    artist_id = cur.fetchone()[0]
        这一段看不明白起什么作用，作用机制是？

第一个是执行cur对象的函数（至于起什么作用，应查看函数的定义），第二个是复制语句。

上面一个是python查询数据库的操作，下面返回Artist表中id的值