Python + Sqlite DB Migration Example Code

db.py

def connect_db():
    """Connects to Database."""
    rv = sqlite3.connect(
        app.config['DATABASE'],
        detect_types=sqlite3.PARSE_DECLTYPES | sqlite3.PARSE_COLNAMES)
    rv.row_factory = sqlite3.Row
    return rv


def get_db():
    """Opens new db connection if there is not an
    existing one for the current app ctx.
    """
    if not hasattr(g, 'sqlite_db'):
        g.sqlite_db = connect_db()
    return g.sqlite_db


def migrate_db():
    """Run database migrations."""

    def get_script_version(path):
        return int(path.split('_')[0].split('/')[1])

    db = get_db()
    current_version = db.cursor().execute('pragma user_version').fetchone()[0]

    directory = os.path.dirname(__file__)
    migrations_path = os.path.join(directory, 'migrations/')
    migration_files = list(os.listdir(migrations_path))
    for migration in sorted(migration_files):
        path = "migrations/{0}".format(migration)
        migration_version = get_script_version(path)

        if migration_version > current_version:
            print("applying migration {0}".format(migration_version))
            with app.open_resource(path, mode='r') as f:
                 db.cursor().executescript(f.read())
                 print("database now at version {0}".format(migration_version))
        else:
            print("migration {0} already applied".format(migration_version))