The contents of the error report are as follows:

File "xxx.py", line 4, in <module>  
  app.run(host='0.0.0.0' , port=80 , debug=true,threaded=False)
  File "/home/xxx/.local/lib/python3.6/site-packages/flask/app.py", line 922, in run
    run_simple(t.cast(str, host), port, self, **options)
  File "/home/xxx/.local/lib/python3.6/site-packages/werkzeug/serving.py", line 982, in run_simple
    s.bind(server_address)
PermissionError: [Errno 13] Permission denied

Looking up the relevant information on the Internet, I found that some people said that under the UNIX environment, ports smaller than 1024 can not be bound by ordinary users, and can only be bound by users with root authority, but using sudo command does not work, so it is necessary to bind a port larger than 1024, and the problem is finally solved

Set port to 8080