python安装以后输入显示是这样，求解
首先这个命令不是在python交互环境下运行的，其次需要使用python -V要大写的V才可以输出版本号，如下：
其它命令说明：
C:\>python --help
usage: python [option] ... [-c cmd | -m mod | file | -] [arg] ...
Options and arguments (and corresponding environment variables):
-b : issue warnings about str(bytes_instance), str(bytearray_instance)
and comparing bytes/bytearray with str. (-bb: issue errors)
-B : don't write .pyc files on import; also PYTHONDONTWRITEBYTECODE=x
-c cmd : program passed in as string (terminates option list)
-d : debug output from parser; also PYTHONDEBUG=x
-E : ignore PYTHON* environment variables (such as PYTHONPATH)
-h : print this help message and exit (also --help)
-i : inspect interactively after running script; forces a prompt even
if stdin does not appear to be a terminal; also PYTHONINSPECT=x
-I : isolate Python from the user's environment (implies -E and -s)
-m mod : run library module as a script (terminates option list)
-O : remove assert and __debug__-dependent statements; add .opt-1 before
.pyc extension; also PYTHONOPTIMIZE=x
-OO : do -O changes and also discard docstrings; add .opt-2 before
.pyc extension
-q : don't print version and copyright messages on interactive startup
-s : don't add user site directory to sys.path; also PYTHONNOUSERSITE
-S : don't imply 'import site' on initialization
-u : force the binary I/O layers of stdout and stderr to be unbuffered;
stdin is always buffered; text I/O layer will be line-buffered;
also PYTHONUNBUFFERED=x
-v : verbose (trace import statements); also PYTHONVERBOSE=x
can be supplied multiple times to increase verbosity
-V : print the Python version number and exit (also --version)
when given twice, print more information about the build
-W arg : warning control; arg is action:message:category:module:lineno
also PYTHONWARNINGS=arg
-x : skip first line of source, allowing use of non-Unix forms of #!cmd
-X opt : set implementation-specific option
file : program read from script file
- : program read from stdin (default; interactive mode if a tty)
arg ...: arguments passed to program in sys.argv[1:]
你输入了python-v，意思是变量python的值减去变量v的值，不过python并没有定义，因此报出错误。
要退出python交互式命令行，按ctrl + z，然后回车，或者输入exit()，然后回车。
要查看python -v的运行情况，请在command line提示符下输入（以C:\开头的这种），然后输入python -v，注意中间有个空格。
