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.

• 当被调用采用 -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!

• 当被调用采用 -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)。

引发 审计事件 cpython.run_command 采用自变量 command .

-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 .

-I option can be used to run the script in isolated mode where sys.path contains neither the current directory nor the user’s site-packages directory. All PYTHON* environment variables are ignored, too.

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

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

引发 审计事件 cpython.run_module 采用自变量 module-name .

另请参阅

runpy.run_module()

等效功能可直接用于 Python 代码

PEP 338 – 将模块作为脚本执行

3.1 版改变： 提供包名称以运行 __main__ 子模块。

3.4 版改变： 还支持名称空间包

-

读取命令从标准输入 ( sys.stdin )。若标准输入是终端， -i 是隐含的。

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 .

引发 审计事件 cpython.run_stdin 不带自变量。

<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。

-I option can be used to run the script in isolated mode where sys.path contains neither the script’s directory nor the user’s site-packages directory. All PYTHON* environment variables are ignored, too.

引发 审计事件 cpython.run_file 采用自变量 filename .

另请参阅

runpy.run_path()

等效功能可直接用于 Python 代码

若未给出接口选项， -i 是隐含的， sys.argv[0] 为空字符串 ( "" ) 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 ¶

打印所有命令行选项的简短描述。

-V ¶

--version ¶

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

Python 3.8.0b2+
											

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

Python 3.8.0b2+ (3.8:0c076caaa8, Apr 20 2019, 21:55:00)
[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 ¶

若给定，Python 不会试着写入 .pyc 文件当导入源模块时。另请参阅 PYTHONDONTWRITEBYTECODE .

--check-hash-based-pycs default|always|never ¶

Control the validation behavior of hash-based .pyc 文件。见 缓存字节码无效 . When set to default , checked and unchecked hash-based bytecode cache files are validated according to their default semantics. When set to always , all hash-based .pyc files, whether checked or unchecked, are validated against their corresponding source file. When set to never , hash-based .pyc files are not validated against their corresponding source files.

The semantics of timestamp-based .pyc files are unaffected by this option.

-d ¶

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

-E ¶

忽略所有 PYTHON* 环境变量，如 PYTHONPATH and PYTHONHOME ，可能有设置。

-i ¶

当传递脚本作为第一自变量或 -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 先于 .pyc 扩展 (见 PEP 488 )。另请参阅 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 先于 .pyc 扩展 (见 PEP 488 ).

3.5 版改变： 修改 .pyc 文件名根据 PEP 488 .

-q ¶

不显示版权和版本消息，即使在交互模式下。

3.2 版新增。

-R ¶

Turn on hash randomization. This option only has an effect if the PYTHONHASHSEED environment variable is set to 0 , since hash randomization is enabled by default.

On previous versions of Python, this option turns on hash randomization, so that the __hash__() values of str and bytes objects 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.

3.7 版改变： 选项不再被忽略。

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 ¶

强制 stdout 和 stderr 流无缓冲。此选项不影响 stdin 流。

另请参阅 PYTHONUNBUFFERED .

3.7 版改变： stdout 和 stderr 流的文本层现在是无缓冲的。

-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 using the PYTHONWARNINGS environment variable and from within a Python program using the warnings 模块。

The simplest settings apply a particular action unconditionally to all warnings emitted by a process (even those that are otherwise ignored by default):

-Wdefault  # Warn once per call location
-Werror    # Convert to exceptions
-Walways   # Warn every time
-Wmodule   # Warn once per calling module
-Wonce     # Warn once per Python process
-Wignore   # Never warn
											

The action names can be abbreviated as desired (e.g. -Wi , -Wd , -Wa , -We ) and the interpreter will resolve them to the appropriate action name.

见 警告过滤 and 描述警告过滤 了解更多细节。

-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 以启用 faulthandler ;

• -X oldparser : enable the traditional LL(1) parser. See also PYTHONOLDPARSER and PEP 617 .

• -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 importtime to show how long each import takes. It shows module name, cumulative time (including nested imports) and self time (excluding nested imports). Note that its output may be broken in multi-threaded application. Typical usage is python3 -X importtime -c 'import asyncio' 。另请参阅 PYTHONPROFILEIMPORTTIME .

• -X dev : enable Python 开发模式 , introducing additional runtime checks that are too expensive to be enabled by default.

• -X utf8 enables UTF-8 mode for operating system interfaces, overriding the default locale-aware mode. -X utf8=0 explicitly disables UTF-8 mode (even when it would otherwise activate automatically). See PYTHONUTF8 了解更多细节。

• -X pycache_prefix=PATH enables writing .pyc files to a parallel tree rooted at the given directory instead of to the code tree. See also PYTHONPYCACHEPREFIX .

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。

3.7 版新增： -X importtime , -X dev and -X utf8 选项。

3.8 版新增： -X pycache_prefix 选项。 -X dev option now logs close() exceptions in io.IOBase 析构函数。

3.9 版改变： 使用 -X dev option, check encoding and errors arguments on string encoding and decoding operations.

-X showalloccount 选项已被移除。

从 3.9 版起弃用，将在 3.10 版中移除： -X oldparser 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 ¶

设置这些变量才有效当调试 Python 构建时。

PYTHONTHREADDEBUG ¶

若设置，Python 将打印线程调试信息。

需要配置 Python 采用 --with-pydebug 构建选项。

PYTHONDUMPREFS ¶

若设置，Python 将转储仍然存活的对象和引用计数在关闭解释器之后。

需要配置 Python 采用 --with-trace-refs 构建选项。