To solve this, set up an application context with app.app_context(). See the documentation for more information.

This typically means that you attempted to use functionality that needed
the current application. To solve this, set up an application context
with app.app_context(). See the documentation for more information.

这个是flask经典问题，属于上下文问题，添加这个下面这个即可。
app.app_context().push()

示例：

app = Flask(__name__)
app.config.from_object(settings.Configs)  # 加载flask项目配置

app.app_context().push()

db=SQLAlchemy(app)    # 创建映射对象,并绑定在app中