1. 命令行和环境 ¶

1.1.1. 接口选项 ¶

The interpreter interface resembles that of the UNIX shell, but provides some additional methods of invocation:

• When called with standard input connected to a tty device, it prompts for commands and executes them until an EOF (an end-of-file character, you can produce that with Ctrl-D on UNIX or Ctrl-Z, Enter on Windows) is read.
• When called with a file name argument or with a file as standard input, it reads and executes a script from that file.
• When called with a directory name argument, it reads and executes an appropriately named script from that directory.
• 当调用采用 -c command , it executes the Python statement(s) given as command . Here command may contain multiple statements separated by newlines. Leading whitespace is significant in Python statements!
• 当调用采用 -m module-name , the given module is located on the Python module path and executed as a script.

In non-interactive mode, the entire input is parsed before it is executed.

An interface option terminates the list of options consumed by the interpreter, all consecutive arguments will end up in sys.argv – note that the first element, subscript zero ( sys.argv[0] ), is a string reflecting the program’s source.

-c <command> ¶

执行 Python 代码在 command . command 可以是由换行符分隔的一条或多条语句，采用如正常模块代码中的显著前导空格。

若给出此选项，第一元素对于 sys.argv 将是 "-c" 且当前目录将被添加到起始在 sys.path (允许该目录下的模块被导入作为顶层模块)。

-m <module-name> ¶

搜索 sys.path for the named module and execute its contents as the __main__ 模块。

由于自变量是 模块 name, you must not give a file extension ( .py ). The module name should be a valid absolute Python module name, but the implementation may not always enforce this (e.g. it may allow you to use a name that includes a hyphen).

Package names (including namespace packages) are also permitted. When a package name is supplied instead of a normal module, the interpreter will execute <pkg>.__main__ as the main module. This behaviour is deliberately similar to the handling of directories and zipfiles that are passed to the interpreter as the script argument.

注意

This option cannot be used with built-in modules and extension modules written in C, since they do not have Python module files. However, it can still be used for precompiled modules, even if the original source file is not available.

若给出此选项，第一元素对于 sys.argv will be the full path to the module file (while the module file is being located, the first element will be set to "-m" ). As with the -c option, the current directory will be added to the start of sys.path .

Many standard library modules contain code that is invoked on their execution as a script. An example is the timeit 模块：

python -mtimeit -s 'setup here' 'benchmarked code here'
python -mtimeit -h # for details
											

另请参阅

runpy.run_module()

Equivalent functionality directly available to Python code

PEP 338 – 将模块作为脚本执行

3.1 版改变： Supply the package name to run a __main__ 子模块。

3.4 版改变： 还支持名称空间包

-

Read commands from standard input ( sys.stdin ). If standard input is a terminal, -i is implied.

若给出此选项，第一元素对于 sys.argv 将是 "-" 且当前目录将被添加到起始在 sys.path .

<script>

Execute the Python code contained in script , which must be a filesystem path (absolute or relative) referring to either a Python file, a directory containing a __main__.py file, or a zipfile containing a __main__.py 文件。

若给出此选项，第一元素对于 sys.argv will be the script name as given on the command line.

If the script name refers directly to a Python file, the directory containing that file is added to the start of sys.path , and the file is executed as the __main__ 模块。

If the script name refers to a directory or zipfile, the script name is added to the start of sys.path 和 __main__.py file in that location is executed as the __main__ 模块。

另请参阅

runpy.run_path()

Equivalent functionality directly available to Python code

If no interface option is given, -i is implied, sys.argv[0] is an empty string ( "" ) and the current directory will be added to the start of sys.path . Also, tab-completion and history editing is automatically enabled, if available on your platform (see Readline 配置 ).

1.1.2. 一般选项 ¶

-? ¶

-h ¶

--help ¶

Print a short description of all command line options.

-V ¶

--version ¶

Print the Python version number and exit. Example output could be:

Python 3.6.0b2+
											

When given twice, print more information about the build, like:

Python 3.6.0b2+ (3.6:84a3c5003510+, Oct 26 2016, 02:33:55)
[GCC 6.2.0 20161005]
											

3.6 版新增： -VV 选项。

1.1.3. 杂项选项 ¶

-b ¶

Issue a warning when comparing bytes or bytearray with str or bytes with int . Issue an error when the option is given twice ( -bb ).

3.5 版改变： Affects comparisons of bytes with int .

-B ¶

If given, Python won’t try to write .pyc files on the import of source modules. See also PYTHONDONTWRITEBYTECODE .

-d ¶

Turn on parser debugging output (for wizards only, depending on compilation options). See also PYTHONDEBUG .

-E ¶

忽略所有 PYTHON* 环境变量，如 PYTHONPATH and PYTHONHOME , that might be set.

-i ¶

When a script is passed as first argument or the -c option is used, enter interactive mode after executing the script or the command, even when sys.stdin does not appear to be a terminal. The PYTHONSTARTUP file is not read.

This can be useful to inspect global variables or a stack trace when a script raises an exception. See also PYTHONINSPECT .

-I ¶

Run Python in isolated mode. This also implies -E and -s. In isolated mode sys.path contains neither the script’s directory nor the user’s site-packages directory. All PYTHON* environment variables are ignored, too. Further restrictions may be imposed to prevent the user from injecting malicious code.

3.4 版新增。

-O ¶

Remove assert statements and any code conditional on the value of __debug__ . Augment the filename for compiled ( bytecode ) files by adding .opt-1 before the .pyc 扩展 (见 PEP 488 ). See also PYTHONOPTIMIZE .

3.5 版改变： 修改 .pyc 文件名根据 PEP 488 .

-OO ¶

Do -O and also discard docstrings. Augment the filename for compiled ( bytecode ) files by adding .opt-2 before the .pyc 扩展 (见 PEP 488 ).

3.5 版改变： 修改 .pyc 文件名根据 PEP 488 .

-q ¶

Don’t display the copyright and version messages even in interactive mode.

3.2 版新增。

-R ¶

Kept for compatibility. On Python 3.3 and greater, hash randomization is turned on by default.

On previous versions of Python, this option turns on hash randomization, so that the __hash__() values of str, bytes and datetime are “salted” with an unpredictable random value. Although they remain constant within an individual Python process, they are not predictable between repeated invocations of Python.

Hash randomization is intended to provide protection against a denial-of-service caused by carefully-chosen inputs that exploit the worst case performance of a dict construction, O(n^2) complexity. See http://www.ocert.org/advisories/ocert-2011-003.html 了解细节。

PYTHONHASHSEED allows you to set a fixed value for the hash seed secret.

3.2.3 版新增。

-s ¶

不添加 user site-packages directory to sys.path .

另请参阅

PEP 370 – 每用户站点包目录

-S ¶

Disable the import of the module site and the site-dependent manipulations of sys.path that it entails. Also disable these manipulations if site is explicitly imported later (call site.main() if you want them to be triggered).

-u ¶

Force the binary layer of the stdout and stderr streams (which is available as their buffer attribute) to be unbuffered. The text I/O layer will still be line-buffered if writing to the console, or block-buffered if redirected to a non-interactive file.

另请参阅 PYTHONUNBUFFERED .

-v ¶

Print a message each time a module is initialized, showing the place (filename or built-in module) from which it is loaded. When given twice ( -vv ), print a message for each file that is checked for when searching for a module. Also provides information on module cleanup at exit. See also PYTHONVERBOSE .

-W arg ¶

Warning control. Python’s warning machinery by default prints warning messages to sys.stderr . A typical warning message has the following form:

file:line: category: message
											

By default, each warning is printed once for each source line where it occurs. This option controls how often warnings are printed.

Multiple -W options may be given; when a warning matches more than one option, the action for the last matching option is performed. Invalid -W options are ignored (though, a warning message is printed about invalid options when the first warning is issued).

Warnings can also be controlled from within a Python program using the warnings 模块。

The simplest form of argument is one of the following action strings (or a unique abbreviation):

ignore

忽略所有警告。

default

Explicitly request the default behavior (printing each warning once per source line).

all

Print a warning each time it occurs (this may generate many messages if a warning is triggered repeatedly for the same source line, such as inside a loop).

模块

Print each warning only the first time it occurs in each module.

once

Print each warning only the first time it occurs in the program.

error

Raise an exception instead of printing a warning message.

The full form of argument is:

action:message:category:module:line
											

Here, action is as explained above but only applies to messages that match the remaining fields. Empty fields match all values; trailing empty fields may be omitted. The message field matches the start of the warning message printed; this match is case-insensitive. The category field matches the warning category. This must be a class name; the match tests whether the actual warning category of the message is a subclass of the specified warning category. The full class name must be given. The 模块 field matches the (fully-qualified) module name; this match is case-sensitive. The line field matches the line number, where zero matches all line numbers and is thus equivalent to an omitted line number.

另请参阅

warnings – the warnings module

PEP 230 – Warning framework

PYTHONWARNINGS

-x ¶

Skip the first line of the source, allowing use of non-Unix forms of #!cmd . This is intended for a DOS specific hack only.

-X ¶

Reserved for various implementation-specific options. CPython currently defines the following possible values:

• -X faulthandler to enable faulthandler ;
• -X showrefcount to output the total reference count and number of used memory blocks when the program finishes or after each statement in the interactive interpreter. This only works on debug builds.
• -X tracemalloc to start tracing Python memory allocations using the tracemalloc module. By default, only the most recent frame is stored in a traceback of a trace. Use -X tracemalloc=NFRAME to start tracing with a traceback limit of NFRAME frames. See the tracemalloc.start() 了解更多信息。
• -X showalloccount to output the total count of allocated objects for each type when the program finishes. This only works when Python was built with COUNT_ALLOCS defined.

It also allows passing arbitrary values and retrieving them through the sys._xoptions 字典。

3.2 版改变： -X 选项被添加。

3.3 版新增： -X faulthandler 选项。

3.4 版新增： -X showrefcount and -X tracemalloc 选项。

3.6 版新增： -X showalloccount 选项。

1.1.4. 不应该使用的选项 ¶

-J ¶

Reserved for use by Jython .

1.2.1. 调试模式变量 ¶

Setting these variables only has an effect in a debug build of Python, that is, if Python was configured with the --with-pydebug build option.

PYTHONTHREADDEBUG ¶

If set, Python will print threading debug info.

PYTHONDUMPREFS ¶

If set, Python will dump objects and reference counts still alive after shutting down the interpreter.