Flask SQLAlchemy: TypeError: ‘Flask’ object is not iterable [duplicate]

def create_app():
    app = Flask(__name__)
    app.config['SECRET_KEY'] = 'kdxhfds iefhsdbf'
    app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///databse.db'
    db.init_app(app)

    ***with app.app_context():
        db.create_all()***