FLASK网址(https://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-i-hello-world)

Chapter 1: Hello, World!

运行

$ flask run

报错

   WARNING: Do not use the development server in a production environment.
   Use a production WSGI server instead.

解决方法：先运行

$ export FLASK_ENV=development

或将 FLASK_ENV=development 写入.flaskenv，再

$ flask run

即可