CPython 解释器扫描命令行和各种设置的环境。
CPython 实现细节： 其它实现的命令行方案可能不同。见 替代实现 为进一步资源。
当援引 Python 时，可以指定这些任何选项：
python [-bBdEhiIOqsSuvVWx?] [-c command | -m module-name | script | - ] [args]
当然，最常见用例是简单援引脚本：
python myscript.py
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
命令
. Here
命令
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.
执行 Python 代码在 命令 . 命令 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
.
搜索
sys.path
for the named module and execute its contents as the
__main__
模块。
由于自变量是
module
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。
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
将是作为在命令行给出的脚本名称。
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
既不包含脚本目录，也不包含用户站点包目录。所有
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
).
另请参阅
3.4 版改变： 自动启用 Tab 补全和历史编辑。
Print a short description of all command line options and corresponding environment variables and exit.
Print a short description of Python-specific environment variables and exit.
3.11 版新增。
Print complete usage information and exit.
3.11 版新增。
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。
Issue a warning when comparing
bytes
or
bytearray
with
str
or
bytes
with
int
. Issue an error when the option is given twice (
-bb
).
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
.
Control the validation behavior of hash-based
.pyc
文件。见
缓存字节码无效
。当设为
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.
打开剖析器调试输出 (仅针对专家，从属编译选项)。另请参阅
PYTHONDEBUG
.
忽略所有
PYTHON*
环境变量，如
PYTHONPATH
and
PYTHONHOME
，可能有设置。
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
.
在隔离模式下运行 Python。这还隐含
-E
,
-P
and
-s
选项。
在隔离模式下
sys.path
既不包含脚本目录，也不包含用户站点包目录。所有
PYTHON*
环境变量也被忽略。可以施加进一步限定以阻止用户注入恶意代码。
3.4 版新增。
移除 assert 语句和任何代码，若代码条件值为
__debug__
。filename 自变量用于编译 (
bytecode
) 文件通过添加
.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
.
Do
-O
且还会丢弃 docstring (文档字符串)。filename 自变量用于编译 (
bytecode
) 文件通过添加
.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
.
不前置潜在不安全路径到
sys.path
:
python -m module
命令行：不前置当前工作目录。
python script.py
命令行：不前置脚本目录。若是符号链接，解析符号链接。
python -c code
and
python
(REPL) 命令行：前置空字符串，意味着当前工作目录。
另请参阅
PYTHONSAFEPATH
环境变量，及
-E
and
-I
(隔离) 选项。
3.11 版新增。
不显示版权和版本消息，即使在交互模式下。
3.2 版新增。
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
允许为哈希种子保密设置固定值。
3.7 版改变： 选项不再被忽略。
3.2.3 版新增。
不添加
user site-packages directory
to
sys.path
.
另请参阅
PEP 370 – 每用户站点包目录
禁用导入模块
site
和从属站点操纵
sys.path
牵涉的。还禁用这些操纵若
site
稍后被明确导入 (调用
site.main()
若想要触发它们)。
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。
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.
3.10 版改变：
site
module reports the site-specific paths and
.pth
files being processed.
另请参阅
PYTHONVERBOSE
.
Warning control. Python’s warning machinery by default prints warning messages to
sys.stderr
.
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 and the interpreter will resolve them to the appropriate action name. For example,
-Wi
如同
-Wignore
.
The full form of argument is:
action:message:category:module:lineno
Empty fields match all values; trailing empty fields may be omitted. For example
-W ignore::DeprecationWarning
ignores all DeprecationWarning warnings.
action field is as explained above but only applies to warnings that match the remaining fields.
message field must match the whole warning message; this match is case-insensitive.
category
field matches the warning category (ex:
DeprecationWarning
). This must be a class name; the match test whether the actual warning category of the message is a subclass of the specified warning category.
module field matches the (fully qualified) module name; this match is case-sensitive.
lineno field matches the line number, where zero matches all line numbers and is thus equivalent to an omitted line number.
多
-W
options can 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
module. For example, the
warnings.filterwarnings()
function can be used to use a regular expression on the warning message.
Skip the first line of the source, allowing use of non-Unix forms of
#!cmd
. This is intended for a DOS specific hack only.
Reserved for various implementation-specific options. CPython currently defines the following possible values:
-X faulthandler
以启用
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 int_max_str_digits
配置
整数字符串转换长度局限性
。另请参阅
PYTHONINTMAXSTRDIGITS
.
-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
：启用
Python 开发模式
，引入默认情况下，启用非常昂贵的额外运行时校验。
-X utf8
启用
Python UTF-8 模式
.
-X utf8=0
明确禁用
Python UTF-8 模式
(even when it would otherwise activate automatically).
-X pycache_prefix=PATH
启用写入
.pyc
files to a parallel tree rooted at the given directory instead of to the code tree. See also
PYTHONPYCACHEPREFIX
.
-X warn_default_encoding
发出
EncodingWarning
when the locale-specific default encoding is used for opening files. See also
PYTHONWARNDEFAULTENCODING
.
-X no_debug_ranges
disables the inclusion of the tables mapping extra location information (end line, start column offset and end column offset) to every instruction in code objects. This is useful when smaller code objects and pyc files are desired as well as suppressing the extra visual location indicators when the interpreter displays tracebacks. See also
PYTHONNODEBUGRANGES
.
-X frozen_modules
determines whether or not frozen modules are ignored by the import machinery. A value of “on” means they get imported and “off” means they are ignored. The default is “on” if this is an installed Python (the normal case). If it’s under development (running from the source tree) then the default is “off”. Note that the “importlib_bootstrap” and “importlib_bootstrap_external” frozen modules are always used, even if this flag is set to “off”.
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
选项现在日志
close()
异常在
io.IOBase
析构函数。
3.9 版改变：
使用
-X dev
选项，校验
encoding
and
errors
自变量在字符串编码和解码操作。
-X showalloccount
选项已被移除。
3.10 版新增：
-X warn_default_encoding
选项。
从 3.9 版起弃用，将在 3.10 版中移除：
-X oldparser
选项。
3.11 版新增：
-X no_debug_ranges
选项。
3.11 版新增：
-X frozen_modules
选项。
3.11 版新增：
-X int_max_str_digits
选项。
更改标准 Python 库的位置。默认情况下，库的搜索是在
prefix/lib/pythonversion
and
exec_prefix/lib/pythonversion
，其中
prefix
and
exec_prefix
安装依赖目录，两者默认为
/usr/local
.
当
PYTHONHOME
被设为单目录，它的值替换
prefix
and
exec_prefix
。要为这些指定不同值，设置
PYTHONHOME
to
prefix:exec_prefix
.
Augment the default search path for module files. The format is the same as the shell’s
PATH
: one or more directory pathnames separated by
os.pathsep
(e.g. colons on Unix or semicolons on Windows). Non-existent directories are silently ignored.
In addition to normal directories, individual
PYTHONPATH
entries may refer to zipfiles containing pure Python modules (in either source or compiled form). Extension modules cannot be imported from zipfiles.
The default search path is installation dependent, but generally begins with
prefix/lib/pythonversion
(见
PYTHONHOME
above). It is
always
appended to
PYTHONPATH
.
An additional directory will be inserted in the search path in front of
PYTHONPATH
as described above under
接口选项
. The search path can be manipulated from within a Python program as the variable
sys.path
.
若把这设为非空字符串，它将覆写
sys.platlibdir
值。
3.9 版新增。
If this is the name of a readable file, the Python commands in that file are executed before the first prompt is displayed in interactive mode. The file is executed in the same namespace where interactive commands are executed so that objects defined or imported in it can be used without qualification in the interactive session. You can also change the prompts
sys.ps1
and
sys.ps2
and the hook
sys.__interactivehook__
in this file.
引发
审计事件
cpython.run_startup
with the filename as the argument when called on startup.
If this is set, it names a callable using dotted-path notation. The module containing the callable will be imported and then the callable will be run by the default implementation of
sys.breakpointhook()
which itself is called by built-in
breakpoint()
. If not set, or set to the empty string, it is equivalent to the value “pdb.set_trace”. Setting this to the string “0” causes the default implementation of
sys.breakpointhook()
to do nothing but return immediately.
3.7 版新增。
若将这设为非空字符串，相当于指定
-i
选项。
此变量也可以被修改通过 Python 代码使用
os.environ
以强制审查模式，当程序终止时。
If this is set to a non-empty string, Python won’t try to write
.pyc
files on the import of source modules. This is equivalent to specifying the
-B
选项。
若设置这，Python 将写入
.pyc
files in a mirror directory tree at this path, instead of in
__pycache__
directories within the source tree. This is equivalent to specifying the
-X
pycache_prefix=PATH
选项。
3.8 版新增。
若此变量未设置或被设为
random
, a random value is used to seed the hashes of str and bytes objects.
若
PYTHONHASHSEED
is set to an integer value, it is used as a fixed seed for generating the hash() of the types covered by the hash randomization.
Its purpose is to allow repeatable hashing, such as for selftests for the interpreter itself, or to allow a cluster of python processes to share hash values.
The integer must be a decimal number in the range [0,4294967295]. Specifying the value 0 will disable hash randomization.
3.2.3 版新增。
If this variable is set to an integer, it is used to configure the interpreter’s global 整数字符串转换长度局限性 .
3.11 版新增。
若在运行解释器之前设置，这会覆盖用于 stdin/stdout/stderr 的编码，按句法
encodingname:errorhandler
。两者
encodingname
和
:errorhandler
部件是可选的，且拥有相同含义如在
str.encode()
.
对于 stderr，
:errorhandler
部分被忽略；处理程序将始终为
'backslashreplace'
.
3.4 版改变：
encodingname
部分现在是可选的。
3.6 版改变：
在 Windows，交互控制台缓冲忽略由此变量指定的编码，除非
PYTHONLEGACYWINDOWSSTDIO
也有指定。透过标准流重定向的文件和管道不受影响。
若设置这，Python 将不添加
user site-packages directory
to
sys.path
.
另请参阅
PEP 370 – 每用户站点包目录
定义
user base directory
, which is used to compute the path of the
user site-packages directory
and
distutils 安装路径
for
python setup.py install --user
.
另请参阅
PEP 370 – 每用户站点包目录
若此环境变量有设置，
sys.argv[0]
will be set to its value instead of the value got through the C runtime. Only works on macOS.
这相当于
-W
option. If set to a comma separated string, it is equivalent to specifying
-W
multiple times, with filters later in the list taking precedence over those earlier in the list.
The simplest settings apply a particular action unconditionally to all warnings emitted by a process (even those that are otherwise ignored by default):
PYTHONWARNINGS=default # Warn once per call location PYTHONWARNINGS=error # Convert to exceptions PYTHONWARNINGS=always # Warn every time PYTHONWARNINGS=module # Warn once per calling module PYTHONWARNINGS=once # Warn once per Python process PYTHONWARNINGS=ignore # Never warn
若此环境变量被设为非空字符串，
faulthandler.enable()
被调用在启动时：安装处理程序为
SIGSEGV
,
SIGFPE
,
SIGABRT
,
SIGBUS
and
SIGILL
信号以转储 Python 回溯。这相当于
-X
faulthandler
选项。
3.3 版新增。
若此环境变量被设为非空字符串，开始跟踪 Python 内存分配使用
tracemalloc
模块。变量的值是存储在跟踪回溯中的最大帧数。例如，
PYTHONTRACEMALLOC=1
仅存储最近帧。见
tracemalloc.start()
了解更多信息。
3.4 版新增。
若此环境变量被设为非空字符串，Python 将展示每次导入花费的时间。这准确相当于设置
-X importtime
在命令行。
3.7 版新增。
设置 Python 内存分配器和/或安装调试挂钩。
设置 Python 使用的内存分配器系列：
default
：使用
默认内存分配器
.
malloc
：使用
malloc()
C 库函数为所有域 （
PYMEM_DOMAIN_RAW
,
PYMEM_DOMAIN_MEM
,
PYMEM_DOMAIN_OBJ
).
pymalloc
：使用
pymalloc 分配器
for
PYMEM_DOMAIN_MEM
and
PYMEM_DOMAIN_OBJ
domains and use the
malloc()
function for the
PYMEM_DOMAIN_RAW
domain.
安装 debug hooks :
debug
：将调试挂钩安装在顶部为
默认内存分配器
.
malloc_debug
：如同
malloc
但还安装调试挂钩。
pymalloc_debug
：如同
pymalloc
但还安装调试挂钩。
3.7 版改变：
添加
"default"
分配器。
3.6 版新增。
If set to a non-empty string, Python will print statistics of the pymalloc 内存分配器 每次创建新 pymalloc 对象 arena 时和关闭时。
This variable is ignored if the
PYTHONMALLOC
environment variable is used to force the
malloc()
allocator of the C library, or if Python is configured without
pymalloc
支持。
3.6 版改变： This variable can now also be used on Python compiled in release mode. It now has no effect if set to an empty string.
If set to a non-empty string, the default 文件系统编码和错误处理程序 mode will revert to their pre-3.6 values of ‘mbcs’ and ‘replace’, respectively. Otherwise, the new defaults ‘utf-8’ and ‘surrogatepass’ are used.
这也可以在运行时被启用采用
sys._enablelegacywindowsfsencoding()
.
可用性 ：Windows。
3.6 版新增： 见 PEP 529 了解更多细节。
若设为非空字符串，不使用新的控制台读取器和写入器。这意味着 Unicode 字符将根据活动控制台代码页编码，而不是使用 UTF-8。
此变量被忽略，若标准流被重定向 (到文件或管道) 而不是引用控制台缓冲。
可用性 ：Windows。
3.6 版新增。
若设为值
0
，导致主 Python 命令行应用程序跳过将传统基于 ASCII 的 C 和 POSIX 区域设置强制转换为能力更强基于 UTF-8 的替代。
若此变量
not
set (or is set to a value other than
0
)，
LC_ALL
locale override environment variable is also not set, and the current locale reported for the
LC_CTYPE
category is either the default
C
locale, or else the explicitly ASCII-based
POSIX
locale, then the Python CLI will attempt to configure the following locales for the
LC_CTYPE
category in the order listed before loading the interpreter runtime:
C.UTF-8
C.utf8
UTF-8
If setting one of these locale categories succeeds, then the
LC_CTYPE
environment variable will also be set accordingly in the current process environment before the Python runtime is initialized. This ensures that in addition to being seen by both the interpreter itself and other locale-aware components running in the same process (such as the GNU
readline
library), the updated setting is also seen in subprocesses (regardless of whether or not those processes are running a Python interpreter), as well as in operations that query the environment rather than the current C locale (such as Python’s own
locale.getdefaultlocale()
).
Configuring one of these locales (either explicitly or via the above implicit locale coercion) automatically enables the
surrogateescape
错误处理程序
for
sys.stdin
and
sys.stdout
(
sys.stderr
继续使用
backslashreplace
as it does in any other locale). This stream handling behavior can be overridden using
PYTHONIOENCODING
as usual.
For debugging purposes, setting
PYTHONCOERCECLOCALE=warn
will cause Python to emit warning messages on
stderr
if either the locale coercion activates, or else if a locale that
would
have triggered coercion is still active when the Python runtime is initialized.
Also note that even when locale coercion is disabled, or when it fails to find a suitable target locale,
PYTHONUTF8
will still activate by default in legacy ASCII-based locales. Both features must be disabled in order to force the interpreter to use
ASCII
而不是
UTF-8
for system interfaces.
可用性 ：Unix。
3.7 版新增： 见 PEP 538 了解更多细节。
若此环境变量被设为非空字符串，启用 Python 开发模式 ，引入默认情况下，启用非常昂贵的额外运行时校验。
3.7 版新增。
若设为
1
，启用
Python UTF-8 模式
.
若设为
0
，禁用
Python UTF-8 模式
.
Setting any other non-empty string causes an error during interpreter initialisation.
3.7 版新增。
If this environment variable is set to a non-empty string, issue a
EncodingWarning
when the locale-specific default encoding is used.
见 选择加入 EncodingWarning 了解细节。
3.10 版新增。
If this variable is set, it disables the inclusion of the tables mapping extra location information (end line, start column offset and end column offset) to every instruction in code objects. This is useful when smaller code objects and pyc files are desired as well as suppressing the extra visual location indicators when the interpreter displays tracebacks.
3.11 版新增。
If set, Python will print threading debug info into stdout.
Deprecated since version 3.10, will be removed in version 3.12.
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。
If set, Python will dump objects and reference counts still alive after shutting down the interpreter into a file called FILENAME .
需要配置 Python 采用
--with-trace-refs
构建选项。
3.11 版新增。