python3 --version 显示“NameError: name 'python3' 未定义”

Question

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

Answer 1

python3 is not Python syntax , it is the Python binary itself , the thing you run to get to the interactive interpreter.

You are confusing the command line with the Python prompt. Open a console (Windows) or terminal (Linux, Mac), the same place you'd use dir or ls to explore your filesystem from the command line.

If you are typing at a >>> or In [number]: prompt you are in the wrong place, that's the Python interpreter itself and it only takes Python syntax. If you started the Python prompt from a command line, exit at this point and go back to the command line. If you started the interpreter from IDLE or in an IDE, then you need to open a terminal or console as a separate program.

Other programs that people often confuse for Python syntax; each of these is actually a program to run in your command prompt:

• python , python2.7 , python3.5 , etc.
• pip or pip3
• virtualenv
• ipython
• easy_install
• django-admin
• conda
• flask
• scrapy
• setup.py -- this is a script you need to run with python setup.py [...] .
• Any of the above together with sudo .

with many more variations possible depending on what tools and libraries you have installed and what you are trying to do.

If given arguments, you'll get a SyntaxError exception instead, but the underlying cause is the same:

>>> pip install foobar
  File "<stdin>", line 1
    pip install foobar
              ^
SyntaxError: invalid syntax

Answer 2

If you're using windows you can try in a Python prompt:

>>>>import pip
>>>>pip.main(['install', 'foobar'])