python: 命令选项及归类

usage: python [option] ... [-c cmd | -m mod | file | -] [arg] ...

Options and arguments (and corresponding environment variables):

-B : don't write .py[co] 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

-m mod : run library module as a script (terminates option list)

-O : optimize generated bytecode slightly; also PYTHONOPTIMIZE=x

-OO : remove doc-strings in addition to the -O optimizations

-R : use a pseudo-random salt to make hash() values of various types be

         unpredictable between separate invocations of the interpreter, as

         a defense against denial-of-service attacks

-Q arg : division options: -Qold (default), -Qwarn, -Qwarnall, -Qnew

-s : don't add user site directory to sys.path; also PYTHONNOUSERSITE

-S : don't imply 'import site' on initialization

-t : issue warnings about inconsistent tab usage (-tt: issue errors)

-u : unbuffered binary stdout and stderr; also PYTHONUNBUFFERED=x

         see man page for details on internal buffering relating to '-u'

-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)

-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

-3 : warn about Python 3.x incompatibilities that 2to3 cannot trivially fix

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:]

Other environment variables:

PYTHONSTARTUP: file executed on interactive startup (no default)

PYTHONPATH : ':'-separated list of directories prefixed to the

               default module search path. The result is sys.path.

PYTHONHOME : alternate <prefix> directory (or <prefix>:<exec_prefix>).

               The default module search path uses <prefix>/pythonX.X.

PYTHONCASEOK : ignore case in 'import' statements (Windows).

PYTHONIOENCODING: Encoding[:errors] used for stdin/stdout/stderr.

PYTHONHASHSEED: if this variable is set to 'random', the effect is the same

   as specifying the -R option: a random value is used to seed the hashes of

   str, bytes and datetime objects. It can also be set to an integer

   in the range [0,4294967295] to get hash values with a predictable seed.

选项分类:

第一类: 执行方式

    (1) -c: command, 执行命令

    (2) -i: interactive, 执行交互

    (3) -m: module, 执行模块

    (4) file: 执行文件

    (5) -: 执行流

    (6) -d: debug模式

第二类: 源码编译

    (1) -B: PYTHONDONTWRITEBYTECODE, 不保存编译后的字节码.

    (2) -E: ignore PYTHON* environment.

    (3) -O, -OO: PYTHONOPTIMIZE, optimize

    (4) -s, -S: PYTHONNOUSERSITE, don't add user site, don't apply import site.

    (5) -t, -tt: Tab与空格共用

    (6) -x: skip x line

    (7) -3: 兼容python3的方式

    (8) -v:  PYTHONVERBOSE

第三类: 特性设置

    (1) -R: hash()方法

    (2) -Q: 除法

    (3) -u: PYTHONUNBUFFERED

第四类: 其他:

    (1) -h

    (2) -V