How to get rid of "SyntaxError: invalid syntax" error when typing pip --version or pip3 --version?

Question

I am trying to use pip or pip3 --version option but both of them give me SyntaxError: invalid syntax error.

masoud@masoud-ThinkPad-E550:~$ pip --version
Traceback (most recent call last):
  File "/home/masoud/.local/bin/pip", line 7, in <module>
    from pip._internal.cli.main import main
  File "/home/masoud/.local/lib/python3.5/site-packages/pip/_internal/cli/main.py", line 60
    sys.stderr.write(f"ERROR: {exc}")
                                   ^
SyntaxError: invalid syntax

And:

masoud@masoud-ThinkPad-E550:~$ pip3 --version
Traceback (most recent call last):
  File "/home/masoud/.local/bin/pip3", line 7, in <module>
    from pip._internal.cli.main import main
  File "/home/masoud/.local/lib/python3.5/site-packages/pip/_internal/cli/main.py", line 60
    sys.stderr.write(f"ERROR: {exc}")
                                   ^
SyntaxError: invalid syntax

How can I fix this? I have seen some fixes by removing some files but I am not sure which directory I need to remove.