这是代码：from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_world():
   return 'Hello World!'

if __name__ == '__main__' :
   app.run(debug=True)

就是在@app.route('/')的‘/’后加什么，就会404报错，或者在return 'Hello World!'后加内容，在网页中也不显示内容。

cmd的内容：

C:\Users\Administrator\Desktop>python test_flask.py

 * Serving Flask app "test_flask" (lazy loading)

 * Environment: production

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

   Use a production WSGI server instead.

 * Debug mode: on

 * Restarting with stat

 * Debugger is active!

 * Debugger PIN: 118-883-086

 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

 * Detected change in 'C:\\Users\\Administrator\\Desktop\\test_flask.py', reload

ing

 * Restarting with stat

 * Debugger is active!

 * Debugger PIN: 118-883-086

 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

不能像课程里面老师在网页上改地址后能够显示内容。