ModuleNotFoundError: No module named 'flask'

错误信息如下:

[root@iZ2ze1asovzc5my2rnfo2lZ app]# python ***.py 
Traceback (most recent call last):
  File "***.py", line 3, in <module>
    import flask
ModuleNotFoundError: No module named 'flask'

执行

pip3 install flask