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  • python -O 有意思的一个信号,Python -的各种模式

    Python脚本中

    一个模块的属性为__debug__

    当python脚本直接运行时,输出为True

    当Python -O命令运行时运行,该参数输出为False。

    python -c参数,支持执行单行命令/脚本。

    python -i其实就是执行文件内容或者执行命令后再进入交互模式。

    python -m以模块方式启动

    有意思的玩意。

    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 stdout and stderr streams to be unbuffered;
             this option has no effect on stdin; 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
    --check-hash-based-pycs always|default|never:
        control how Python invalidates hash-based .pyc files
    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>/lib/pythonX.X.
    PYTHONCASEOK : ignore case in 'import' statements (Windows).
    PYTHONIOENCODING: Encoding[:errors] used for stdin/stdout/stderr.
    PYTHONFAULTHANDLER: dump the Python traceback on fatal errors.
    PYTHONHASHSEED: if this variable is set to 'random', 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.
    PYTHONMALLOC: set the Python memory allocators and/or install debug hooks
       on Python memory allocators. Use PYTHONMALLOC=debug to install debug
       hooks.
    PYTHONCOERCECLOCALE: if this variable is set to 0, it disables the locale
       coercion behavior. Use PYTHONCOERCECLOCALE=warn to request display of
       locale coercion and locale compatibility warnings on stderr.
    PYTHONBREAKPOINT: if this variable is set to 0, it disables the default
       debugger. It can be set to the callable of your debugger of choice.
    PYTHONDEVMODE: enable the development mode.

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  • 原文地址:https://www.cnblogs.com/sidianok/p/12328024.html
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