python - 新人按着flask教程一步一步的走,报错..求指导...

教程地址:http://docs.jinkan.org/docs/flask/tutorial/dbinit.html#tutorial-dbinit

# all the imports                                          
import sqlite3

from flask import Flask, request, session, g, redirect, url    _for, abort, render_template, flash
# configuration
DATABASE = '/tmp/flaskr.db'
DEBUG = True
SECRET_KEY = 'development key'
USERNAME = 'admin'
PASSWORD = 'default'

#create our little application 
app = Flask(__name__)
app.config.from_envvar('FLASKR_SETTINGS', silent=True)

def connect_db():
    return sqlite3.connect(app.config['DATABASE'])

def init_db():
    with closing(connect_db()) as db:
        with app.open_resource('schema.sql') as f:
            db.cursor().executescript(f.read())
        db.commit()
if __name__ == '__main__':
    app.run()

>>> init_db()
Traceback (most recent call last):
  File "", line 1, in 
  File "flaskr.py", line 18, in init_db
    with closing(connect_db()) as db:
NameError: global name 'closing' is not defined