pip3 "TypeError: 'module' object is not callable" after update

The solution which worked for my situation is simply editing the pip3.8 file in the ubuntu environment.

Method1:

#!/path/to/.venv/bin/python3
# -*- coding: utf-8 -*-
import re
import sys

from pip._internal.main import main  # <--- look at this import statement! 

if __name__ == '__main__':
     sys.argv[0] = re.sub(r'(-script\.pyw?|\.exe)?$', '', sys.argv[0])
     sys.exit(main())

method2:

The main function has to be imported or we can simply replace line

sys.exit(main())

As

sys.exit(main.main())

From the link by Bram, I just ran python3 -m pip uninstall pip, and it started to work again.