mysql+flask _sqlalchemy报错

Question

跟着书本FlaskWeb开发学到第七章调整项目结构的时候，使用flask_sqlalchemy 出现UserWarning: Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set 的警告
这是config.py代码

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
import os
app = Flask(__name__)

basedir = os.path.abspath(os.path.dirname(__file__))

class Config:
    app.config['SECRET_KEY'] = 'hard to guess string'
    app.config['MAIL_DEFAULT_SENDER'] = '[e-mail]'  # 填邮箱，默认发送者
    app.config['SECRET_KEY'] = 'hard to guess string'
    app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://root:430202@127.0.0.1:3306/test1'
    app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = True
    app.config['SQLALCHEMY_COMMIT_ON_TEARDOWN'] = True


    app.config['FLASKY_ADMIN'] = '[e-mail]'

    @staticmethod
    def init_app(app):
        pass

class DevelopmentConfig(Config):
    DEBUG = True
    app.config['MAIL_SERVER'] = 'smtp.qq.com'
    app.config['MAIL_PORT'] = 587
    app.config['MAIL_USE_TLS'] = True
    app.config['MAIL_USERNAME'] = '[e-mail]'
    app.config['MAIL_PASSWORD'] = 'ddjogvrpawyebcdi'
    app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://root:430202@127.0.0.1:3306/test1'
    app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = True
    app.config['SQLALCHEMY_COMMIT_ON_TEARDOWN'] = True


class TestingConfig(Config):
    TESTING = True
    app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://root:430202@127.0.0.1:3306/test1'


class ProductionConfig(Config):
    app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://root:430202@127.0.0.1:3306/test1'


config = {
    'development': DevelopmentConfig,
    'testing': TestingConfig,
    'production': ProductionConfig,
    'default': DevelopmentConfig

}

这是app__init__.py代码

from flask import Flask, render_template
from flask_bootstrap import Bootstrap
from flask_mail import Mail
from flask_moment import Moment
from flask_sqlalchemy import SQLAlchemy
from config import config
from flask_login import LoginManager

bootstrap = Bootstrap()
mail = Mail()
moment = Moment()
db = SQLAlchemy()
login_manager=LoginManager()
login_manager.session_protection='strong'
login_manager.login_view='auth.login'


def create_app(config_name):
    app = Flask(__name__)
    app.config.from_object(config[config_name])
    config[config_name].init_app(app)
    bootstrap.init_app(app)
    mail.init_app(app)
    moment.init_app(app)
    db.init_app(app)
    login_manager.init_app(app)

    from .main import main as main_blueprint
    app.register_blueprint(main_blueprint)

    from .auth import auth as auth_blueprint
    app.register_blueprint(auth_blueprint,url_prefix='/auth')

# 附加路由和自定义的错误页面

    return app

这是test文件

import unittest
from flask import current_app
from app import create_app, db


class BasicsTestCase(unittest.TestCase):
    def setUp(self):
        self.app = create_app('testing')
        self.app_context = self.app.app_context()
        self.app_context.push()
        db.create_all()
    def tearDown(self):
        db.session.remove()
        db.drop_all()
        self.app_context.pop()

    def test_app_exists(self):
        self.assertFalse(current_app is None)

    def test_app_is_testing(self):
        self.assertTrue(current_app.config['TESTING'])

运行python manage.py test的时候报错信息如下：
C:UsersDELLPycharmProjectsbookvenvlibsite-packagesflask_sqlalchemy__init__.py:774: UserWarning: Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set. Defaulting SQLALCHEMY_DATABASE_URI to "sqlite:///:memory:".
'Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set. '
test_app_exists (test_basic.BasicsTestCase) ... C:UsersDELLPycharmProjectsbookvenvlibsite-packagesflask_sqlalchemy__init__.py:774: UserWarning: Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set. Defaulting SQLALCHEMY_DATABASE_URI to "sqlite:///:memory:".
'Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set. '
目前把网上有类似问题的解决方案都尝试过了，还是没有解决，真的不知道问题出在哪，有人帮忙看一下吗？

Answer 1

把 Config 类里的 app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://root:430202@127.0.0.1:3306/test1'去掉。

Answer 2

我将congfig文件中的app.config['xxx']修改成['xxx']='xxx'的格式就不会出现这个提醒了，例如将
app.config['SECRET_KEY'] = 'hard to guess string'修改为 SECRET_KEY = 'hard to guess string'
不知道原因，但是确实这样操作后就没有警告了