Solve the problem that python still reports the error ModuleNotFoundError: No module named 'xxx' after installing the xxx module

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Background & Problem Description

Recently I encountered a very magical problem. The module that had been installed through pip3 pydubsuddenly became unusable and an error was reported.

ModuleNotFoundError: No module named 'pydub'

When executed pip3 list | grep pydub, there is corresponding output, proving that it has indeed been installed.

$ pip3 list | grep pydub
pydub                 0.25.1

I also had the same problem after trying it reinstall. I searched online for a long time and found no effective solution.
However, after my investigation, I finally found the problem:

$ python3 -V
Python 3.6.8

$ which python3  
/usr/bin/python3

$ ls -l /usr/bin/python3
lrwxrwxrwx 1 root root 9 Jun 27 11:26 /usr/bin/python3 -> python3.6

$ pip3 -V               
pip 23.1.2 from /usr/local/python3/lib/python3.8/site-packages/pip (python 3.8)

It was found that the python version pointed to by this command is inconsistent with the python versionpython3 pointed by pip3 . This is the problem.

solution

Just set the python version pip3pointed python3to to the same path. In my environment, I set it to the 3.8 version corresponding to pip3, which is achieved by modifying the soft link:

$ ln -s /usr/local/python3/bin/python3.8 /usr/bin/python3

Verify whether the modification is successful

$ which python3 
/usr/bin/python3

$ ls -l /usr/bin/python3                                     
lrwxrwxrwx 1 root root 32 Jul 13 17:32 /usr/bin/python3 -> /usr/local/python3/bin/python3.8

$ python3             
Python 3.8.1 (default, Feb  9 2023, 20:00:12) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-44)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pydub
>>> 

OK, no problem. At this point, the problem is solved.