When Run a command in the terminal called:

C:\Python39\python.exe -m pip install --upgrade pip

Below WARNING: error is happen.

WARNING: Ignoring invalid distribution -ip (c:\python39\lib\site-packages)

C:\WINDOWS\system32>C:\Python39\python.exe -m pip install --upgrade pip
WARNING: Ignoring invalid distribution -ip (c:\python39\lib\site-packages)
WARNING: Ignoring invalid distribution -ip (c:\python39\lib\site-packages)
Requirement already satisfied: pip in c:\python39\lib\site-packages (21.2.3)
Collecting pip
  Using cached pip-21.2.4-py3-none-any.whl (1.6 MB)
WARNING: Ignoring invalid distribution -ip (c:\python39\lib\site-packages)
Installing collected packages: pip
  Attempting uninstall: pip
    WARNING: Ignoring invalid distribution -ip (c:\python39\lib\site-packages)
    Found existing installation: pip 21.2.3
    Uninstalling pip-21.2.3:
      Successfully uninstalled pip-21.2.3
WARNING: Ignoring invalid distribution -ip (c:\python39\lib\site-packages)
Successfully installed pip-21.2.4
WARNING: Ignoring invalid distribution -ip (c:\python39\lib\site-packages)
WARNING: Ignoring invalid distribution -ip (c:\python39\lib\site-packages)
WARNING: Ignoring invalid distribution -ip (c:\python39\lib\site-packages)

Here is the solution below.

Go to the error path. In my case it is c:\python39\lib\site-packages. And delete the folder.

Here below image there is no error.