text: from flask import Flask
  from flask_sqlalchemy import SQLAlchemy
  from flask_bootstrap import Bootstrap
  from flask_moment import Moment
  from flask_debugtoolbar import DebugToolbarExtension
  #当使用包组织代码时，为了确保其他扩展或测试框架获得正确的路径值
  # 最好以硬编码的形式写出包名称作为程序名称，即sayhello
  app = Flask('sayhello')
  app.config.from_pyfile('settings.py')
  app.jinja_env.trim_blocks = True
  app.jinja_env.lstrip_blocks = True
  db = SQLAlchemy(app)
  bootstrap = Bootstrap(app)
  moment = Moment(app)
  app.debug = True
  toobar = DebugToolbarExtension(app)
  from sayhello import views, errors, commands