python3 --version shows "NameError: name 'python3' is not defined"

When we type

python3 --version (or --V)

it is supposed to show us the version of the python right?

However, when I do this I get the following error:

NameError: name 'python3' is not defined

This is also the case when I tried to install the pip by using

>>> python3 get-pip.py
  File "<stdin>", line 1
    python3 get-pip.py
              ^
SyntaxError: invalid syntax