Creating Database by exporting file from XML

Question

My application is to read an export file in XML and produce a properly normalized database. Well The application is running and printing results as well as storing in database but in the middle an error pops out and the program halts- Note- DataSet is proper format. It is coursera Question-

I Like To Fight Kaiser Chiefs Yours Truly, Angry Mob 15 218566 None Alternative & Punk
From The Neck Down Kaiser Chiefs Yours Truly, Angry Mob 15 147226 None Alternative & Punk
Bomb Squad (TECH) Brent Brent's Album None 208065 None None    
Traceback (most recent call last):
      File "C:\Users\Dhruv\misctrack.py", line 75, in <module>
        genre_id= cur.fetchone()[0]
    TypeError: 'NoneType' object has no attribute '__getitem__'

Following is the complete program. I am given complete program because I was suggested last time. If it's inappropriate please inform.

import sqlite3
import xml.etree.ElementTree as ET
conn=sqlite3.connect('misctrackdb.sqlite')
cur=conn.cursor()

cur.executescript(''' 
DROP TABLE IF EXISTS Artist;
DROP TABLE IF EXISTS Album;
DROP TABLE IF EXISTS Track;
DROP TABLE IF EXISTS Genre;

CREATE TABLE Artist(
id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT UNIQUE,
name TEXT UNIQUE
);

CREATE TABLE Genre(
id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT UNIQUE,
name TEXT UNIQUE
);

CREATE TABLE Album(
id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT UNIQUE,
title TEXT UNIQUE,
artist_id INTEGER
);

CREATE TABLE Track (
id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT UNIQUE,
title TEXT UNIQUE,
genre_id INTEGER,
album_id INTEGER,
len INTEGER,rating INTEGER, count INTEGER
);

''')
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


fle=raw_input("Enter File HEre")
stuff=ET.parse(fle)
all=stuff.findall('dict/dict/dict')
print 'Dict count:', len(all)

for line in all:
    if lookup(line,'Track ID') is None: 
        continue
    #print "1"
    name=lookup(line,'Name')
    album=lookup(line,'Album')
    genre=lookup(line,'Genre')
    artist=lookup(line,'Artist')
    count=lookup(line,'Track Count')
    len=lookup(line,'Total Time')
    rating=lookup(line,'Rating')
    #print "2"

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

    print name, artist ,album ,count ,len, rating, genre

    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 Genre (name) 
    VALUES(?)''',(genre,))
    cur.execute('SELECT id FROM Genre WHERE name=?',(genre,))
    genre_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 Track (title,genre_id,album_id,len,rating,count)
    VALUES(?,?,?,?,?,?)''',(album,genre_id,album_id,len,rating,count))
    conn.commit()

Please help me in sorting out the issue. I have been stuck for 2 days in this issue.

Answer 1

cur.execute('SELECT id FROM Genre WHERE name=?',(genre,))

Returns None (nothing), so when you try to to access the first element, you get your error.

Since you cannot be sure that there will always be a genre to be returned, it would be cleaner to wrap these things into a try.. except structure which prints the error, but continues anyway.