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`sys` — 特定系统参数和函数 ¶

此模块提供对由解释器使用或维护的一些变量的访问，及对与解释器强交互函数的访问。它始终可用。

sys. abiflags ¶

在 POSIX 系统构建 Python 采用标准 configure 脚本，这包含 ABI 标志作为指定通过 PEP 3149 .

Added in version 3.2.

3.8 版改变：默认标志变成空字符串 ( m 标志对于 pymalloc 已被移除)。

可用性：Unix。

sys. addaudithook ( hook ) ¶

追加可调用 hook 到当前 (子) 解释器的活动审计挂钩列表。

当审计事件被引发透过 sys.audit() 函数，每个挂钩将按添加事件名称和自变量元组的次序被调用。本机挂钩的添加通过 PySys_AddAuditHook() 被首先调用，紧接着是在当前 (子) 解释器中添加的挂钩。然后挂钩可以日志事件，引发异常中止操作 (或完全终止进程)。

Note that audit hooks are primarily for collecting information about internal or otherwise unobservable actions, whether by Python or libraries written in Python. They are not suitable for implementing a “sandbox”. In particular, malicious code can trivially disable or bypass hooks added using this function. At a minimum, any security-sensitive hooks must be added using the C API PySys_AddAuditHook() before initialising the runtime, and any modules allowing arbitrary memory modification (such as ctypes ) should be completely removed or closely monitored.

调用 sys.addaudithook() 自身会引发审计事件命名 sys.addaudithook 不带自变量。若任何现有挂钩引发的异常派生自 RuntimeError ，新的挂钩不会被添加且异常被抑制。因此，调用者不可以假定它们的挂钩已添加，除非控制所有现有挂钩。

见审计事件表了解由 CPython 引发的所有事件，和 PEP 578 了解原始设计讨论。

Added in version 3.8.

3.8.1 版改变：异常派生自 Exception 而非 RuntimeError 不再被抑制。

CPython 实现细节： 当跟踪被启用 (见 settrace() )，Python 挂钩才被跟踪若可调用拥有 __cantrace__ 成员 (被设为 True 值)。否则，跟踪函数将跳过挂钩。

sys. argv ¶

传递给 Python 脚本的命令行自变量列表。 argv[0] 是脚本名称 (它是否为完整路径名从属操作系统)。若命令的执行是使用 -c 命令行选项到解释器， argv[0] 被设为字符串 '-c' 。若脚本名称未被传递给 Python 解释器， argv[0] 是空字符串。

要循环标准输入或命令行中给出的文件列表，见 fileinput 模块。

另请参阅 sys.orig_argv .

注意

在 Unix，命令行自变量从 OS 按字节传递。Python 采用文件系统编码和 surrogateescape (替代转义) 错误处理程序解码它们。当需要原始字节时，可以获取它通过 [os.fsencode(arg) for arg in sys.argv] .

sys. audit ( event , * args ) ¶

引发审计事件并触发任何活动审计挂钩。 event 是标识事件的字符串，和 args 可能包含具有有关事件更多信息的可选自变量。给定事件的自变量数和类型被视为是公共且稳定的 API，和不应该在不同发行之间修改。

例如，某个审计事件名为 os.chdir 。此事件有一自变量称为 path 将包含请求的新工作目录。

sys.audit() 将调用现有审计挂钩，传递事件名称和自变量，并从任何挂钩重新引发第一个异常。一般而言，若异常被引发，则不应处理它且应尽快终止进程。这允许挂钩实现决定如何响应特定事件：它们只能日志事件，或通过引发异常中止操作。

添加挂钩使用 sys.addaudithook() or PySys_AddAuditHook() 函数。

此函数的本机等效为 PySys_Audit() 。首选使用本机函数，当可能时。

见审计事件表了解由 CPython 引发的所有事件。

Added in version 3.8.

sys. base_exec_prefix ¶

在 Python 启动期间设置，先于 site.py 的运行，到相同值如 exec_prefix 。若未运行在虚拟环境，值将保持不变；若 site.py finds that a virtual environment is in use, the values of prefix and exec_prefix will be changed to point to the virtual environment, whereas base_prefix and base_exec_prefix will remain pointing to the base Python installation (the one which the virtual environment was created from).

Added in version 3.3.

sys. base_prefix ¶

在 Python 启动期间设置，先于 site.py 的运行，到相同值如 prefix 。若未运行在虚拟环境，值将保持不变；若 site.py finds that a virtual environment is in use, the values of prefix and exec_prefix will be changed to point to the virtual environment, whereas base_prefix and base_exec_prefix will remain pointing to the base Python installation (the one which the virtual environment was created from).

Added in version 3.3.

sys. byteorder ¶: An indicator of the native byte order. This will have the value 'big' on big-endian (most-significant byte first) platforms, and 'little' on little-endian (least-significant byte first) platforms.

sys. builtin_module_names ¶

包含编译进此 Python 解释器的所有模块名称的字符串元组 (此信息不可用按任何其它方式 — modules.keys() 只列表导入模块)。

另请参阅 sys.stdlib_module_names 列表。

sys. call_tracing ( func , args ) ¶

调用 func(*args) , while tracing is enabled. The tracing state is saved, and restored afterwards. This is intended to be called from a debugger from a checkpoint, to recursively debug or profile some other code.

Tracing is suspended while calling a tracing function set by settrace() or setprofile() to avoid infinite recursion. call_tracing() enables explicit recursion of the tracing function.

sys. copyright ¶: 包含 Python 解释器版权归属的字符串。

sys. _clear_type_cache ( ) ¶

Clear the internal type cache. The type cache is used to speed up attribute and method lookups. Use the function only to drop unnecessary references during reference leak debugging.

此功能只应用于内部和专用目的。

sys. _current_frames ( ) ¶

返回将每个线程的标识符，映射到在该线程中目前处于活动状态 (当调用函数时) 的最顶层堆栈帧的字典。注意，该函数在 traceback 模块可以构建给出这样的帧的调用堆栈。

This is most useful for debugging deadlock: this function does not require the deadlocked threads’ cooperation, and such threads’ call stacks are frozen for as long as they remain deadlocked. The frame returned for a non-deadlocked thread may bear no relationship to that thread’s current activity by the time calling code examines the frame.

此功能只应用于内部和专用目的。

引发审计事件 sys._current_frames 不带自变量。

sys. _current_exceptions ( ) ¶

Return a dictionary mapping each thread’s identifier to the topmost exception currently active in that thread at the time the function is called. If a thread is not currently handling an exception, it is not included in the result dictionary.

This is most useful for statistical profiling.

此功能只应用于内部和专用目的。

引发审计事件 sys._current_exceptions 不带自变量。

Changed in version 3.12: Each value in the dictionary is now a single exception instance, rather than a 3-tuple as returned from sys.exc_info() .

sys. breakpointhook ( ) ¶

此挂钩函数被调用通过内置 breakpoint() . By default, it drops you into the pdb debugger, but it can be set to any other function so that you can choose which debugger gets used.

The signature of this function is dependent on what it calls. For example, the default binding (e.g. pdb.set_trace() ) expects no arguments, but you might bind it to a function that expects additional arguments (positional and/or keyword). The built-in breakpoint() function passes its *args and **kws straight through. Whatever breakpointhooks() returns is returned from breakpoint() .

The default implementation first consults the environment variable PYTHONBREAKPOINT . If that is set to "0" then this function returns immediately; i.e. it is a no-op. If the environment variable is not set, or is set to the empty string, pdb.set_trace() is called. Otherwise this variable should name a function to run, using Python’s dotted-import nomenclature, e.g. package.subpackage.module.function 。在此情况下， package.subpackage.module would be imported and the resulting module must have a callable named function() . This is run, passing in *args and **kws , and whatever function() 返回， sys.breakpointhook() 返回到内置 breakpoint() 函数。

Note that if anything goes wrong while importing the callable named by PYTHONBREAKPOINT ， RuntimeWarning is reported and the breakpoint is ignored.

另请注意：若 sys.breakpointhook() 以编程方式覆写， PYTHONBREAKPOINT is not consulted.

Added in version 3.7.

sys. _debugmallocstats ( ) ¶

将 CPython 内存分配器状态的有关低级信息，打印到标 stderr。

If Python is built in debug mode ( configure --with-pydebug option ), it also performs some expensive internal consistency checks.

Added in version 3.3.

CPython 实现细节： This function is specific to CPython. The exact output format is not defined here, and may change.

sys. dllhandle ¶: 指定 Python DLL 句柄的整数。

可用性：Windows。

sys. displayhook ( value ) ¶

若 value 不是 None ，此函数打印 repr(value) to sys.stdout ，并保存 value in builtins._ 。若 repr(value) 不可编码成 sys.stdout.encoding with sys.stdout.errors 错误处理程序 (可能是 'strict' )，就将它编码成 sys.stdout.encoding with 'backslashreplace' 错误处理程序。

sys.displayhook 被调用当为结果估算表达式进入交互 Python 会话。可以定制这些值的显示，通过将另一 1 自变量函数赋值给 sys.displayhook .

伪代码：

def displayhook(value):
    if value is None:
        return
    # Set '_' to None to avoid recursion
    builtins._ = None
    text = repr(value)
    try:
        sys.stdout.write(text)
    except UnicodeEncodeError:
        bytes = text.encode(sys.stdout.encoding, 'backslashreplace')
        if hasattr(sys.stdout, 'buffer'):
            sys.stdout.buffer.write(bytes)
        else:
            text = bytes.decode(sys.stdout.encoding, 'strict')
            sys.stdout.write(text)
    sys.stdout.write("\n")
    builtins._ = value

3.2 版改变：使用 'backslashreplace' 错误处理程序当 UnicodeEncodeError .

sys. dont_write_bytecode ¶: 若这为 True，Python 不会试着写入 .pyc 文件当导入源模块时。此值最初被设为 True or False 从属 -B 命令行选项和 PYTHONDONTWRITEBYTECODE 环境变量，但自己可以设置它以控制字节码文件的生成。

sys. _emscripten_info ¶

A 命名元组 holding information about the environment on the wasm32-emscripten platform. The named tuple is provisional and may change in the future.

_emscripten_info. emscripten_version ¶: Emscripten version as tuple of ints (major, minor, micro), e.g. (3, 1, 8) .

_emscripten_info. runtime ¶: 运行时字符串，如浏览器用户代理 'Node.js v14.18.2' ，或 'UNKNOWN' .

_emscripten_info. pthreads ¶: True if Python is compiled with Emscripten pthreads support.

_emscripten_info. shared_memory ¶: True if Python is compiled with shared memory support.

可用性 : Emscripten.

Added in version 3.11.

sys. pycache_prefix ¶

若设置这 (非 None )，Python 将写入字节码缓存 .pyc 文件到 (和读取它们从) 根于此目录的平行目录树，而不是从 __pycache__ 目录在源代码树中。任何 __pycache__ 目录在源代码树中会被忽略且新 .pyc 文件会被写入在 pycache 前缀下。因此，若使用 compileall 作为预构建步骤，必须确保采用如运行时使用的相同 pycache 前缀 (若有的话) 来运行它。

相对路径的解释相对于当前工作目录。

此值的最初设置是基于值源于 -X pycache_prefix=PATH 命令行选项或 PYTHONPYCACHEPREFIX 环境变量 (命令行优先)。若两者均未设置，则为 None .

Added in version 3.8.

sys. excepthook ( type , value , traceback ) ¶

此函数将给定回溯和异常输出到 sys.stderr .

When an exception other than SystemExit is raised and uncaught, the interpreter calls sys.excepthook 采用异常类、异常实例和回溯对象 3 自变量。在交互会话中，这恰好发生在控制返回给提示之前；在 Python 程序中，这恰好发生在程序退出之前。这种顶层异常的处理可以定制，通过赋值另一 3 自变量函数给 sys.excepthook .

引发审计事件 sys.excepthook 采用自变量 hook , type , value , traceback 当出现未捕获异常时。若没有设置挂钩， hook 可以是 None 。若任何挂钩引发的异常派生自 RuntimeError 对挂钩的调用将被抑制。否则，审计挂钩异常将被报告为不可引发且 sys.excepthook 将被调用。

另请参阅

The sys.unraisablehook() 函数处理不可引发异常和 threading.excepthook() 函数处理的异常引发通过 threading.Thread.run() .

sys. __breakpointhook__ ¶

sys. __displayhook__ ¶

sys. __excepthook__ ¶

sys. __unraisablehook__ ¶

这些对象包含原始值的 breakpointhook , displayhook , excepthook ，和 unraisablehook 在程序启动时。保存它们以便 breakpointhook , displayhook and excepthook , unraisablehook 可以还原若发生以损坏 (或替代) 对象替换它们。

Added in version 3.7: __breakpointhook__

Added in version 3.8: __unraisablehook__

sys. exception ( ) ¶

This function, when called while an exception handler is executing (such as an except or except* clause), returns the exception instance that was caught by this handler. When exception handlers are nested within one another, only the exception handled by the innermost handler is accessible.

If no exception handler is executing, this function returns None .

Added in version 3.11.

sys. exc_info ( ) ¶

This function returns the old-style representation of the handled exception. If an exception e is currently handled (so exception() would return e ), exc_info() returns the tuple (type(e), e, e.__traceback__) . That is, a tuple containing the type of the exception (a subclass of BaseException ), the exception itself, and a 回溯对象 which typically encapsulates the call stack at the point where the exception last occurred.

If no exception is being handled anywhere on the stack, this function return a tuple containing three None 值。

3.11 版改变： The type and traceback fields are now derived from the value (the exception instance), so when an exception is modified while it is being handled, the changes are reflected in the results of subsequent calls to exc_info() .

sys. exec_prefix ¶

A string giving the site-specific directory prefix where the platform-dependent Python files are installed; by default, this is also '/usr/local' . This can be set at build time with the --exec-prefix 自变量到 configure script. Specifically, all configuration files (e.g. the pyconfig.h header file) are installed in the directory exec_prefix/lib/pythonX.Y/config , and shared library modules are installed in exec_prefix/lib/pythonX.Y/lib-dynload ，其中 X.Y is the version number of Python, for example 3.2 .

注意

若虚拟环境 is in effect, this value will be changed in site.py to point to the virtual environment. The value for the Python installation will still be available, via base_exec_prefix .

sys. executable ¶: 给出 Python 解释器可执行二进制文件绝对路径的字符串，若在系统中这有意义。若 Python 无法检索到其可执行文件的真实路径， sys.executable 将是空字符串或 None .

sys. exit ( [ arg ] ) ¶

引发 SystemExit exception, signaling an intention to exit the interpreter.

可选自变量 arg can be an integer giving the exit status (defaulting to zero), or another type of object. If it is an integer, zero is considered “successful termination” and any nonzero value is considered “abnormal termination” by shells and the like. Most systems require it to be in the range 0–127, and produce undefined results otherwise. Some systems have a convention for assigning specific meanings to specific exit codes, but these are generally underdeveloped; Unix programs generally use 2 for command line syntax errors and 1 for all other kind of errors. If another type of object is passed, None is equivalent to passing zero, and any other object is printed to stderr and results in an exit code of 1. In particular, sys.exit("some error message") is a quick way to exit a program when an error occurs.

由于 exit() ultimately “only” raises an exception, it will only exit the process when called from the main thread, and the exception is not intercepted. Cleanup actions specified by finally clauses of try 语句的承兑，且在外层拦截退出尝试是可能的。

3.6 版改变： If an error occurs in the cleanup after the Python interpreter has caught SystemExit (such as an error flushing buffered data in the standard streams), the exit status is changed to 120.

sys. flags ¶

The 命名元组 flags 暴露命令行标志状态。属性只读。

标志。 debug ¶	`-d`
标志。 inspect ¶	`-i`
标志。 interactive ¶	`-i`
标志。 isolated ¶	`-I`
标志。 optimize ¶	`-O` or `-OO`
标志。 dont_write_bytecode ¶	`-B`
标志。 no_user_site ¶	`-s`
标志。 no_site ¶	`-S`
标志。 ignore_environment ¶	`-E`
标志。 verbose ¶	`-v`
标志。 bytes_warning ¶	`-b`
标志。 quiet ¶	`-q`
标志。 hash_randomization ¶	`-R`
标志。 dev_mode ¶	`-X dev` ( Python 开发模式 )
标志。 utf8_mode ¶	`-X utf8`
标志。 safe_path ¶	`-P`
标志。 int_max_str_digits ¶	`-X int_max_str_digits` ( 整数字符串转换长度局限性 )
标志。 warn_default_encoding ¶	`-X warn_default_encoding`

3.2 版改变：添加 quiet 属性为新 -q 标志。

Added in version 3.2.3: The hash_randomization 属性。

3.3 版改变：移除过时 division_warning 属性。

3.4 版改变：添加 isolated 属性为 -I isolated 标志。

3.7 版改变：添加 dev_mode 属性为新 Python 开发模式和 utf8_mode 属性为新 -X utf8 标志。

3.10 版改变：添加 warn_default_encoding 属性为 -X warn_default_encoding 标志。

3.11 版改变：添加 safe_path 属性为 -P 选项。

3.11 版改变：添加 int_max_str_digits 属性。

sys. float_info ¶

A 命名元组 holding information about the float type. It contains low level information about the precision and internal representation. The values correspond to the various floating-point constants defined in the standard header file float.h for the ‘C’ programming language; see section 5.2.4.2.2 of the 1999 ISO/IEC C standard [C99] , ‘Characteristics of floating types’, for details.

Attributes of the `float_info` 命名元组 ¶
属性	float.h 宏	解释
float_info. epsilon ¶	`DBL_EPSILON`	difference between 1.0 and the least value greater than 1.0 that is representable as a float. 另请参阅 `math.ulp()` .
float_info. dig ¶	`DBL_DIG`	The maximum number of decimal digits that can be faithfully represented in a float; see below.
float_info. mant_dig ¶	`DBL_MANT_DIG`	Float precision: the number of base- `radix` digits in the significand of a float.
float_info. max ¶	`DBL_MAX`	The maximum representable positive finite float.
float_info. max_exp ¶	`DBL_MAX_EXP`	The maximum integer e 这样 `radix**(e-1)` is a representable finite float.
float_info. max_10_exp ¶	`DBL_MAX_10_EXP`	The maximum integer e 这样 `10**e` is in the range of representable finite floats.
float_info. min ¶	`DBL_MIN`	The minimum representable positive normalized float. 使用 `math.ulp(0.0)` to get the smallest positive denormalized representable float.
float_info. min_exp ¶	`DBL_MIN_EXP`	The minimum integer e 这样 `radix**(e-1)` is a normalized float.
float_info. min_10_exp ¶	`DBL_MIN_10_EXP`	The minimum integer e 这样 `10**e` is a normalized float.
float_info. radix ¶	`FLT_RADIX`	The radix of exponent representation.
float_info. rounds ¶	`FLT_ROUNDS`	An integer representing the rounding mode for floating-point arithmetic. This reflects the value of the system `FLT_ROUNDS` macro at interpreter startup time: `-1` : indeterminable `0` : toward zero `1` : to nearest `2` : toward positive infinity `3` : toward negative infinity All other values for `FLT_ROUNDS` characterize implementation-defined rounding behavior.

属性 sys.float_info.dig needs further explanation. If s is any string representing a decimal number with at most sys.float_info.dig significant digits, then converting s to a float and back again will recover a string representing the same decimal value:

>>> import sys
>>> sys.float_info.dig
15
>>> s = '3.14159265358979'    # decimal string with 15 significant digits
>>> format(float(s), '.15g')  # convert to float and back -> same value
'3.14159265358979'

But for strings with more than sys.float_info.dig significant digits, this isn’t always true:

>>> s = '9876543211234567'    # 16 significant digits is too many!
>>> format(float(s), '.16g')  # conversion changes value
'9876543211234568'

sys. float_repr_style ¶

A string indicating how the repr() function behaves for floats. If the string has value 'short' then for a finite float x , repr(x) aims to produce a short string with the property that float(repr(x)) == x . This is the usual behaviour in Python 3.1 and later. Otherwise, float_repr_style has value 'legacy' and repr(x) behaves in the same way as it did in versions of Python prior to 3.1.

Added in version 3.1.

sys. getallocatedblocks ( ) ¶

Return the number of memory blocks currently allocated by the interpreter, regardless of their size. This function is mainly useful for tracking and debugging memory leaks. Because of the interpreter’s internal caches, the result can vary from call to call; you may have to call _clear_type_cache() and gc.collect() to get more predictable results.

If a Python build or implementation cannot reasonably compute this information, getallocatedblocks() is allowed to return 0 instead.

Added in version 3.4.

sys. getunicodeinternedsize ( ) ¶

Return the number of unicode objects that have been interned.

3.12 版添加。

sys. getandroidapilevel ( ) ¶: 以整数形式返回构建 Android 时的 API 版本。

可用性：Android。

Added in version 3.7.

sys. getdefaultencoding ( ) ¶: Return the name of the current default string encoding used by the Unicode implementation.

sys. getdlopenflags ( ) ¶: Return the current value of the flags that are used for dlopen() calls. Symbolic names for the flag values can be found in the os 模块 ( RTLD_xxx constants, e.g. os.RTLD_LAZY ).

可用性：Unix。

sys. getfilesystemencoding ( ) ¶

获取文件系统编码：编码用于文件系统错误处理程序以在 Unicode 文件名和 bytes 文件名之间转换。文件系统错误处理程序的返回来自 getfilesystemencodeerrors() .

为最佳兼容性，在所有情况下文件名应使用 str，尽管还支持将文件名表示成 bytes。接受 (或返回) 文件名的函数应支持 str 或 bytes，并在内部转换为系统的首选表示。

os.fsencode() and os.fsdecode() 应用于确保使用正确编码和错误模式。

The 文件系统编码和错误处理程序的配置是在 Python 启动时通过 PyConfig_Read() 函数：见 filesystem_encoding and filesystem_errors 成员对于 PyConfig .

3.2 版改变： getfilesystemencoding() 结果不可以是 None 不再。

3.6 版改变： Windows 不再保证返回 'mbcs' 。见 PEP 529 and _enablelegacywindowsfsencoding() 了解更多信息。

3.7 版改变：返回 'utf-8' 若 Python UTF-8 模式被启用。

sys. getfilesystemencodeerrors ( ) ¶

获取文件系统错误处理程序：错误处理程序用于文件系统编码在 Unicode 文件名和 bytes 文件名之间转换。文件系统编码的返回来自 getfilesystemencoding() .

os.fsencode() and os.fsdecode() 应用于确保使用正确编码和错误模式。

The 文件系统编码和错误处理程序的配置是在 Python 启动时通过 PyConfig_Read() 函数：见 filesystem_encoding and filesystem_errors 成员对于 PyConfig .

Added in version 3.6.

sys. get_int_max_str_digits ( ) ¶

返回当前值为整数字符串转换长度局限性。另请参阅 set_int_max_str_digits() .

Added in version 3.11.

sys. getrefcount ( object ) ¶

返回引用计数为 object 。一般来说，返回计数可能比期望大 1，因为它包含 (临时) 引用作为自变量在 getrefcount() .

Note that the returned value may not actually reflect how many references to the object are actually held. For example, some objects are “immortal” and have a very high refcount that does not reflect the actual number of references. Consequently, do not rely on the returned value to be accurate, other than a value of 0 or 1.

Changed in version 3.12: Immortal objects have very large refcounts that do not match the actual number of references to the object.

sys. getrecursionlimit ( ) ¶: 返回递归限制的当前值 (Python 解释器堆栈的最大深度)。此限制阻止导致 C 堆栈溢出和 Python 崩溃的无限递归。可以设置它通过 setrecursionlimit() .

sys. getsizeof ( object [ , default ] ) ¶

返回对象的大小，以字节为单位。对象可以是任何类型的对象。所有内置对象会返回正确结果，但对于第 3 方扩展而言这不一定正确，因为它是特定实现。

Only the memory consumption directly attributed to the object is accounted for, not the memory consumption of objects it refers to.

若给定， default will be returned if the object does not provide means to retrieve the size. Otherwise a TypeError 会被引发。

getsizeof() 调用对象的 __sizeof__ method and adds an additional garbage collector overhead if the object is managed by the garbage collector.

见递归大小配方例如使用 getsizeof() 递归查找容器大小及其所有内容。

sys. getswitchinterval ( ) ¶

返回解释器的 "线程切换间隔"；见 setswitchinterval() .

Added in version 3.2.

sys. _getframe ( [ depth ] ) ¶

从调用堆栈返回帧对象。若可选整数 depth 有给定，返回堆栈顶部下多个调用帧对象。若比调用堆栈更深， ValueError 被引发。默认 depth 为 0，返回调用堆栈顶部帧。

引发审计事件 sys._getframe 采用自变量 frame .

CPython 实现细节： 此函数只应用于内部和专用目的。它不保证在所有 Python 实现中均存在。

sys. _getframemodulename ( [ depth ] ) ¶

Return the name of a module from the call stack. If optional integer depth is given, return the module that many calls below the top of the stack. If that is deeper than the call stack, or if the module is unidentifiable, None is returned. The default for depth is zero, returning the module at the top of the call stack.

引发审计事件 sys._getframemodulename 采用自变量 depth .

CPython 实现细节： 此函数只应用于内部和专用目的。它不保证在所有 Python 实现中均存在。

sys. getprofile ( ) ¶: 获取剖分析器函数如设置通过 setprofile() .

sys. gettrace ( ) ¶

获取跟踪函数如设置通过 settrace() .

CPython 实现细节： The gettrace() function is intended only for implementing debuggers, profilers, coverage tools and the like. Its behavior is part of the implementation platform, rather than part of the language definition, and thus may not be available in all Python implementations.

sys. getwindowsversion ( ) ¶

Return a named tuple describing the Windows version currently running. The named elements are major , minor , build , platform , service_pack , service_pack_minor , service_pack_major , suite_mask , product_type and platform_version . service_pack contains a string, platform_version a 3-tuple and all other values are integers. The components can also be accessed by name, so sys.getwindowsversion()[0] 相当于 sys.getwindowsversion().major . For compatibility with prior versions, only the first 5 elements are retrievable by indexing.

platform 将是 2 (VER_PLATFORM_WIN32_NT).

product_type may be one of the following values:

常量	含义
`1` (VER_NT_WORKSTATION)	系统是工作站。
`2` (VER_NT_DOMAIN_CONTROLLER)	系统是域控制器。
`3` (VER_NT_SERVER)	系统是服务器，但不是域控制器。

此函数包裹 Win32 GetVersionEx() function; see the Microsoft documentation on OSVERSIONINFOEX() for more information about these fields.

platform_version returns the major version, minor version and build number of the current operating system, rather than the version that is being emulated for the process. It is intended for use in logging rather than for feature detection.

注意

platform_version derives the version from kernel32.dll which can be of a different version than the OS version. Please use platform module for achieving accurate OS version.

可用性：Windows。

3.2 版改变： Changed to a named tuple and added service_pack_minor , service_pack_major , suite_mask ，和 product_type .

3.6 版改变：添加 platform_version

sys. get_asyncgen_hooks ( ) ¶

返回 asyncgen_hooks object, which is similar to a namedtuple of the form (firstiter, finalizer) ，其中 firstiter and finalizer are expected to be either None or functions which take an 异步生成器迭代器 as an argument, and are used to schedule finalization of an asynchronous generator by an event loop.

Added in version 3.6: 见 PEP 525 了解更多细节。

注意

此函数已添加到暂行基础 (见 PEP 411 了解细节。)

sys. get_coroutine_origin_tracking_depth ( ) ¶

Get the current coroutine origin tracking depth, as set by set_coroutine_origin_tracking_depth() .

Added in version 3.7.

注意

此函数已添加到暂行基础 (见 PEP 411 了解细节)。仅用于调试目的。

sys. hash_info ¶

A 命名元组 giving parameters of the numeric hash implementation. For more details about hashing of numeric types, see 数值类型的哈希 .

hash_info. width ¶: The width in bits used for hash values

hash_info. modulus ¶: The prime modulus P used for numeric hash scheme

hash_info. inf ¶: The hash value returned for a positive infinity

hash_info. nan ¶: (This attribute is no longer used)

hash_info. imag ¶: The multiplier used for the imaginary part of a complex number

hash_info. algorithm ¶: The name of the algorithm for hashing of str, bytes, and memoryview

hash_info. hash_bits ¶: The internal output size of the hash algorithm

hash_info. seed_bits ¶: The size of the seed key of the hash algorithm

Added in version 3.2.

3.4 版改变：添加 algorithm , hash_bits and seed_bits

sys. hexversion ¶

The version number encoded as a single integer. This is guaranteed to increase with each version, including proper support for non-production releases. For example, to test that the Python interpreter is at least version 1.5.2, use:

if sys.hexversion >= 0x010502F0:
    # use some advanced feature
    ...
else:
    # use an alternative implementation or warn the user
    ...

This is called hexversion since it only really looks meaningful when viewed as the result of passing it to the built-in hex() 函数。命名元组 sys.version_info may be used for a more human-friendly encoding of the same information.

更多细节对于 hexversion 可以找到在 API 和 ABI 版本控制 .

sys. 实现 ¶

包含目前运行 Python 解释器实现有关信息的对象。下列属性被要求存在于所有 Python 实现中。

name 是实现的标识符，如 'cpython' 。实际字符串由 Python 实现定义，但它保证是小写。

version is a named tuple, in the same format as sys.version_info . It represents the version of the Python 实现 . This has a distinct meaning from the specific version of the Python 语言 to which the currently running interpreter conforms, which sys.version_info represents. For example, for PyPy 1.8 sys.implementation.version 可以是 sys.version_info(1, 8, 0, 'final', 0) ，而 sys.version_info 将为 sys.version_info(2, 7, 2, 'final', 0) . For CPython they are the same value, since it is the reference implementation.

hexversion is the implementation version in hexadecimal format, like sys.hexversion .

cache_tag is the tag used by the import machinery in the filenames of cached modules. By convention, it would be a composite of the implementation’s name and version, like 'cpython-33' . However, a Python implementation may use some other value if appropriate. If cache_tag 被设为 None , it indicates that module caching should be disabled.

sys.implementation may contain additional attributes specific to the Python implementation. These non-standard attributes must start with an underscore, and are not described here. Regardless of its contents, sys.implementation will not change during a run of the interpreter, nor between implementation versions. (It may change between Python language versions, however.) See PEP 421 了解更多信息。

Added in version 3.3.

注意

The addition of new required attributes must go through the normal PEP process. See PEP 421 了解更多信息。

sys. int_info ¶

A 命名元组 that holds information about Python’s internal representation of integers. The attributes are read only.

int_info. bits_per_digit ¶: The number of bits held in each digit. Python integers are stored internally in base 2**int_info.bits_per_digit .

int_info. sizeof_digit ¶: The size in bytes of the C type used to represent a digit.

int_info. default_max_str_digits ¶: 默认值对于 sys.get_int_max_str_digits() when it is not otherwise explicitly configured.

int_info. str_digits_check_threshold ¶: The minimum non-zero value for sys.set_int_max_str_digits() , PYTHONINTMAXSTRDIGITS ，或 -X int_max_str_digits .

Added in version 3.1.

3.11 版改变：添加 default_max_str_digits and str_digits_check_threshold .

sys. __interactivehook__ ¶

When this attribute exists, its value is automatically called (with no arguments) when the interpreter is launched in 交互模式 . This is done after the PYTHONSTARTUP file is read, so that you can set this hook there. The site 模块 sets this .

引发审计事件 cpython.run_interactivehook with the hook object as the argument when the hook is called on startup.

Added in version 3.4.

sys. intern ( string ) ¶

Enter string in the table of “interned” strings and return the interned string – which is string itself or a copy. Interning strings is useful to gain a little performance on dictionary lookup – if the keys in a dictionary are interned, and the lookup key is interned, the key comparisons (after hashing) can be done by a pointer compare instead of a string compare. Normally, the names used in Python programs are automatically interned, and the dictionaries used to hold module, class or instance attributes have interned keys.

Interned strings are not immortal; you must keep a reference to the return value of intern() around to benefit from it.

sys. is_finalizing ( ) ¶

返回 True 若 Python 解释器是关闭 , False 否则。

Added in version 3.5.

sys. last_exc ¶

This variable is not always defined; it is set to the exception instance when an exception is not handled and the interpreter prints an error message and a stack traceback. Its intended use is to allow an interactive user to import a debugger module and engage in post-mortem debugging without having to re-execute the command that caused the error. (Typical use is import pdb; pdb.pm() to enter the post-mortem debugger; see pdb module for more information.)

3.12 版添加。

sys. last_type ¶
sys. last_value ¶
sys. last_traceback ¶: These three variables are deprecated; use sys.last_exc instead. They hold the legacy representation of sys.last_exc , as returned from exc_info() above.

sys. maxsize ¶: An integer giving the maximum value a variable of type Py_ssize_t can take. It’s usually 2**31 - 1 在 32 位平台和 2**63 - 1 在 64 位平台。

sys. maxunicode ¶

An integer giving the value of the largest Unicode code point, i.e. 1114111 ( 0x10FFFF in hexadecimal).

3.3 版改变： Before PEP 393 , sys.maxunicode used to be either 0xFFFF or 0x10FFFF , depending on the configuration option that specified whether Unicode characters were stored as UCS-2 or UCS-4.

sys. meta_path ¶

列表化的元路径查找器对象拥有 find_spec() methods called to see if one of the objects can find the module to be imported. By default, it holds entries that implement Python’s default import semantics. The find_spec() method is called with at least the absolute name of the module being imported. If the module to be imported is contained in a package, then the parent package’s __path__ attribute is passed in as a second argument. The method returns a 模块特定，或 None if the module cannot be found.

另请参阅

importlib.abc.MetaPathFinder: The abstract base class defining the interface of finder objects on meta_path .
importlib.machinery.ModuleSpec: 具体类 find_spec() 应返回实例。

3.4 版改变：模块特定在 Python 3.4 引入，由 PEP 451 .

Changed in version 3.12: Removed the fallback that looked for a find_module() method if a meta_path entry didn’t have a find_spec() 方法。

sys. 模块 ¶: 这是将模块名映射到已加载模块的字典。可以操纵这以强制重新加载模块及其它技巧。不管怎样，替换字典不一定如期望般工作且从字典删除必需项可能导致 Python 失败。若想要遍历此全局字典，始终使用 sys.modules.copy() or tuple(sys.modules) 以避免异常，由于其大小可能在迭代期间因其它线程中的代码 (或活动) 的副作用而改变。

sys. orig_argv ¶

The list of the original command line arguments passed to the Python executable.

The elements of sys.orig_argv are the arguments to the Python interpreter, while the elements of sys.argv are the arguments to the user’s program. Arguments consumed by the interpreter itself will be present in sys.orig_argv and missing from sys.argv .

Added in version 3.10.

sys. path ¶

指定模块搜索路径的字符串列表。初始化自环境变量 PYTHONPATH ，加从属安装默认。

默认情况下，程序启动时如初始化，前置潜在不安全路径到 sys.path ( before 插入条目作为结果对于 PYTHONPATH ):

python -m module 命令行：前置当前工作目录。
python script.py 命令行：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。

为不前置这种潜在不安全路径，使用 -P 命令行选项或 PYTHONSAFEPATH 环境变量。

A program is free to modify this list for its own purposes. Only strings should be added to sys.path ; all other data types are ignored during import.

另请参阅

模块 site 这描述如何使用 .pth 文件扩展 sys.path .

sys. path_hooks ¶

A list of callables that take a path argument to try to create a finder for the path. If a finder can be created, it is to be returned by the callable, else raise ImportError .

最初的指定在 PEP 302 .

sys. path_importer_cache ¶

字典充当缓存对于 finder objects. The keys are paths that have been passed to sys.path_hooks and the values are the finders that are found. If a path is a valid file system path but no finder is found on sys.path_hooks then None 是存储。

最初的指定在 PEP 302 .

sys. platform ¶

This string contains a platform identifier that can be used to append platform-specific components to sys.path ，例如。

For Unix systems, except on Linux and AIX, this is the lowercased OS name as returned by uname -s with the first part of the version as returned by uname -r appended, e.g. 'sunos5' or 'freebsd8' , at the time when Python was built . Unless you want to test for a specific system version, it is therefore recommended to use the following idiom:

if sys.platform.startswith('freebsd'):
    # FreeBSD-specific code here...
elif sys.platform.startswith('linux'):
    # Linux-specific code here...
elif sys.platform.startswith('aix'):
    # AIX-specific code here...

对于其它系统，值是：

系统	`platform` 值
AIX	`'aix'`
Emscripten	`'emscripten'`
Linux	`'linux'`
WASI	`'wasi'`
Windows	`'win32'`
Windows/Cygwin	`'cygwin'`
macOS	`'darwin'`

3.3 版改变：在 Linux， sys.platform 不再包含主要版本。它始终是 'linux' ，而不是 'linux2' or 'linux3' . Since older Python versions include the version number, it is recommended to always use the startswith idiom presented above.

3.8 版改变： On AIX, sys.platform 不再包含主要版本。它始终是 'aix' ，而不是 'aix5' or 'aix7' . Since older Python versions include the version number, it is recommended to always use the startswith idiom presented above.

另请参阅

os.name 拥有更粗的粒度。 os.uname() 给出系统从属版本信息。

The platform 模块提供系统身份的详细校验。

sys. platlibdir ¶

Name of the platform-specific library directory. It is used to build the path of standard library and the paths of installed extension modules.

它等于 "lib" on most platforms. On Fedora and SuSE, it is equal to "lib64" on 64-bit platforms which gives the following sys.path paths (where X.Y is the Python major.minor version):

/usr/lib64/pythonX.Y/ ：标准库 (像 os.py 的 os 模块)
/usr/lib64/pythonX.Y/lib-dynload/ ：标准库的 C 扩展模块 (像 errno module, the exact filename is platform specific)
/usr/lib/pythonX.Y/site-packages/ (始终使用 lib , not sys.platlibdir )：第 3 方模块
/usr/lib64/pythonX.Y/site-packages/ ：第 3 方包的 C 扩展模块

Added in version 3.9.

sys. prefix ¶

A string giving the site-specific directory prefix where the platform independent Python files are installed; on Unix, the default is /usr/local . This can be set at build time with the --prefix 自变量到 configure 脚本。见安装路径对于派生路径。

注意

若虚拟环境 is in effect, this value will be changed in site.py to point to the virtual environment. The value for the Python installation will still be available, via base_prefix .

sys. ps1 ¶
sys. ps2 ¶: Strings specifying the primary and secondary prompt of the interpreter. These are only defined if the interpreter is in interactive mode. Their initial values in this case are '>>> ' and '... ' . If a non-string object is assigned to either variable, its str() is re-evaluated each time the interpreter prepares to read a new interactive command; this can be used to implement a dynamic prompt.

sys. setdlopenflags ( n ) ¶: Set the flags used by the interpreter for dlopen() calls, such as when the interpreter loads extension modules. Among other things, this will enable a lazy resolving of symbols when importing a module, if called as sys.setdlopenflags(0) . To share symbols across extension modules, call as sys.setdlopenflags(os.RTLD_GLOBAL) . Symbolic names for the flag values can be found in the os 模块 ( RTLD_xxx constants, e.g. os.RTLD_LAZY ).

可用性：Unix。

sys. set_int_max_str_digits ( maxdigits ) ¶

设置整数字符串转换长度局限性用于此解释器。另请参阅 get_int_max_str_digits() .

Added in version 3.11.

sys. setprofile ( profilefunc ) ¶

Set the system’s profile function, which allows you to implement a Python source code profiler in Python. See chapter Python 剖分析器 for more information on the Python profiler. The system’s profile function is called similarly to the system’s trace function (see settrace() ), but it is called with different events, for example it isn’t called for each executed line of code (only on call and return, but the return event is reported even when an exception has been set). The function is thread-specific, but there is no way for the profiler to know about context switches between threads, so it does not make sense to use this in the presence of multiple threads. Also, its return value is not used, so it can simply return None . Error in the profile function will cause itself unset.

注意

The same tracing mechanism is used for setprofile() as settrace() . To trace calls with setprofile() inside a tracing function (e.g. in a debugger breakpoint), see call_tracing() .

Profile functions should have three arguments: frame , event ，和 arg . frame is the current stack frame. event is a string: 'call' , 'return' , 'c_call' , 'c_return' ，或 'c_exception' . arg depends on the event type.

事件拥有下列含义：

'call': A function is called (or some other code block entered). The profile function is called; arg is None .
'return': A function (or other code block) is about to return. The profile function is called; arg is the value that will be returned, or None if the event is caused by an exception being raised.
'c_call': A C function is about to be called. This may be an extension function or a built-in. arg 是 C 函数对象。
'c_return': A C function has returned. arg 是 C 函数对象。
'c_exception': C 函数引发异常。 arg 是 C 函数对象。

引发审计事件 sys.setprofile 不带自变量。

sys. setrecursionlimit ( limit ) ¶

将 Python 解释器堆栈的最大深度设为 limit 。此限制阻止导致 C 堆栈溢出和 Python 崩溃的无限递归。

可能的最高限制从属平台。用户可能需要将限制设置得更高，当程序要求深入递归且平台支持更高限制时。应该小心这样做，因为过高的限制可能导致崩溃。

若当前递归深度的新限制过低， RecursionError 异常被引发。

3.5.1 版改变： A RecursionError 异常现在引发，若新限制在当前递归深度处太低。

sys. setswitchinterval ( interval ) ¶

设置解释器的线程切换间隔 (以秒为单位)。此浮点值确定分配给并发运行 Python 线程的 "时间切片" 的理想持续时间。请注意，实际值可以更高，尤其是使用长时间运行内部函数或方法。另外，间隔结束时变为调度哪个线程，由操作系统决策。解释器没有自己的调度器。

Added in version 3.2.

sys. settrace ( tracefunc ) ¶

Set the system’s trace function, which allows you to implement a Python source code debugger in Python. The function is thread-specific; for a debugger to support multiple threads, it must register a trace function using settrace() for each thread being debugged or use threading.settrace() .

Trace functions should have three arguments: frame , event ，和 arg . frame is the current stack frame. event is a string: 'call' , 'line' , 'return' , 'exception' or 'opcode' . arg depends on the event type.

跟踪函数是援引 (采用 event 设为 'call' ) whenever a new local scope is entered; it should return a reference to a local trace function to be used for the new scope, or None if the scope shouldn’t be traced.

The local trace function should return a reference to itself, or to another function which would then be used as the local trace function for the scope.

If there is any error occurred in the trace function, it will be unset, just like settrace(None) 被调用。

注意

Tracing is disabled while calling the trace function (e.g. a function set by settrace() ). For recursive tracing see call_tracing() .

事件拥有下列含义：

'call': A function is called (or some other code block entered). The global trace function is called; arg is None ; the return value specifies the local trace function.
'line': The interpreter is about to execute a new line of code or re-execute the condition of a loop. The local trace function is called; arg is None ; the return value specifies the new local trace function. See Objects/lnotab_notes.txt for a detailed explanation of how this works. Per-line events may be disabled for a frame by setting f_trace_lines to False on that frame .
'return': A function (or other code block) is about to return. The local trace function is called; arg is the value that will be returned, or None if the event is caused by an exception being raised. The trace function’s return value is ignored.
'exception': 出现异常。调用局部跟踪函数； arg 是元组 (exception, value, traceback) ；返回值指定新的本地跟踪函数。
'opcode': The interpreter is about to execute a new opcode (see dis for opcode details). The local trace function is called; arg is None ; the return value specifies the new local trace function. Per-opcode events are not emitted by default: they must be explicitly requested by setting f_trace_opcodes to True 在 frame .

注意，由于异常沿调用者链向下传播， 'exception' 事件会在每级生成。

For more fine-grained usage, it’s possible to set a trace function by assigning frame.f_trace = tracefunc explicitly, rather than relying on it being set indirectly via the return value from an already installed trace function. This is also required for activating the trace function on the current frame, which settrace() doesn’t do. Note that in order for this to work, a global tracing function must have been installed with settrace() in order to enable the runtime tracing machinery, but it doesn’t need to be the same tracing function (e.g. it could be a low overhead tracing function that simply returns None to disable itself immediately on each frame).

For more information on code and frame objects, refer to 标准类型层次结构 .

引发审计事件 sys.settrace 不带自变量。

CPython 实现细节： The settrace() function is intended only for implementing debuggers, profilers, coverage tools and the like. Its behavior is part of the implementation platform, rather than part of the language definition, and thus may not be available in all Python implementations.

3.7 版改变： 'opcode' 事件类型被添加； f_trace_lines and f_trace_opcodes 属性被添加到帧

Changed in version 3.12: 'opcode' event will only be emitted if f_trace_opcodes of at least one frame has been set to True before settrace() is called. This behavior will be changed back in 3.13 to be consistent with previous versions.

sys. set_asyncgen_hooks ( [firstiter] [, finalizer] ) ¶

Accepts two optional keyword arguments which are callables that accept an 异步生成器迭代器作为自变量。 firstiter callable will be called when an asynchronous generator is iterated for the first time. The finalizer will be called when an asynchronous generator is about to be garbage collected.

引发审计事件 sys.set_asyncgen_hooks_firstiter 不带自变量。

引发审计事件 sys.set_asyncgen_hooks_finalizer 不带自变量。

Two auditing events are raised because the underlying API consists of two calls, each of which must raise its own event.

Added in version 3.6: 见 PEP 525 for more details, and for a reference example of a finalizer method see the implementation of asyncio.Loop.shutdown_asyncgens in Lib/asyncio/base_events.py

注意

此函数已添加到暂行基础 (见 PEP 411 了解细节。)

sys. set_coroutine_origin_tracking_depth ( depth ) ¶

Allows enabling or disabling coroutine origin tracking. When enabled, the cr_origin attribute on coroutine objects will contain a tuple of (filename, line number, function name) tuples describing the traceback where the coroutine object was created, with the most recent call first. When disabled, cr_origin 将是 None .

To enable, pass a depth value greater than zero; this sets the number of frames whose information will be captured. To disable, pass set depth to zero.

此设置是线程特定的。

Added in version 3.7.

注意

此函数已添加到暂行基础 (见 PEP 411 了解细节)。仅用于调试目的。

sys. activate_stack_trampoline ( backend , / ) ¶

Activate the stack profiler trampoline backend . The only supported backend is "perf" .

可用性：Linux。

3.12 版添加。

另请参阅

sys. deactivate_stack_trampoline ( ) ¶

Deactivate the current stack profiler trampoline backend.

If no stack profiler is activated, this function has no effect.

可用性：Linux。

3.12 版添加。

sys. is_stack_trampoline_active ( ) ¶: 返回 True if a stack profiler trampoline is active.

可用性：Linux。

3.12 版添加。

sys. _enablelegacywindowsfsencoding ( ) ¶

更改文件系统编码和错误处理程序 to ‘mbcs’ and ‘replace’ respectively, for consistency with versions of Python prior to 3.6.

这相当于定义 PYTHONLEGACYWINDOWSFSENCODING 环境变量在启动 Python 之前。

另请参阅 sys.getfilesystemencoding() and sys.getfilesystemencodeerrors() .

可用性：Windows。

Added in version 3.6: 见 PEP 529 了解更多细节。

sys. stdin ¶

sys. stdout ¶

sys. stderr ¶

文件对象用于解释器为标准输入、标准输出及标准错误：

stdin 用于所有交互输入 (包括调用 input() );
stdout 用于输出源自 print() and 表达式语句及提示对于 input() ;
解释器自己的提示及其错误消息转到 stderr .

这些流是常规文本文件像那些返回通过 open() 函数。它们参数的选取如下：

编码和错误处理的初始化是从 PyConfig.stdio_encoding and PyConfig.stdio_errors .

在 Windows，控制台设备使用 UTF-8。非字符设备，如磁盘文件和管道使用系统区域设置编码 (即 ANSI 代码页)。非控制台字符设备，如 NUL (即 isatty() 返回 True ) 在启动时使用控制台 "输入/输出" 代码页的值，分别用于 stdin 和 stdout/stderr。这默认为系统区域设置编码若进程最初没有附加到控制台。

可以覆盖控制台的特殊行为，通过在启动 Python 之前设置 PYTHONLEGACYWINDOWSSTDIO 环境变量。在此情况下，任何其它字符设备将使用控制台代码页。

在所有平台，可以覆盖字符编码通过设置 PYTHONIOENCODING 环境变量在启动 Python 之前，或通过使用新的 -X utf8 命令行选项和 PYTHONUTF8 环境变量。不管怎样，对于 Windows 控制台，这才应用当 PYTHONLEGACYWINDOWSSTDIO 也有设置。
当交互时， stdout 流为行缓冲。否则，像常规文本文件块缓冲。 stderr 流在这两种情况下都是行缓冲。可以使这 2 种流无缓冲通过传递 -u 命令行选项或设置 PYTHONUNBUFFERED 环境变量。

3.9 版改变：非交互 stderr 现在是行缓冲而不是完全缓冲。

注意

要写入 (或读取) 二进制数据从/到标准流，使用底层二进制 buffer 对象。例如：要写入 bytes 到 stdout ，使用 sys.stdout.buffer.write(b'abc') .

不管怎样，若正编写库 (且不控制其代码在上下文中的执行)，注意，标准流可能被替换为像文件对象，如 io.StringIO 不支持 buffer 属性。

sys. __stdin__ ¶

sys. __stdout__ ¶

sys. __stderr__ ¶

这些对象包含原始值的 stdin , stderr and stdout 当程序启动时。在定稿期间使用它们，可以打印到实际标准流不管是否 sys.std* 对象已被重定向。

还可以用于将实际文件还原到已知工作文件对象，若它们被破坏对象所覆写。不管怎样，首选方式是在替换它之前明确保存先前流，再还原保存对象。

注意

在某些条件下 stdin , stdout and stderr 及原始值 __stdin__ , __stdout__ and __stderr__ 可以是 None 。通常是这种情况，对于未连接到控制台的 Windows GUI APP 和 Python APP 启动采用 pythonw .

sys. stdlib_module_names ¶

包含标准库模块名称的字符串冻结集。

在所有平台是一样的。还会列出在某些平台不可用的模块和 Python 构建时的禁用模块。列出所有模块种类：纯 Python、内置、冻结及扩展模块。排除测试模块。

对于包，只列出主包：不会列出子包和子模块。例如， email 包会列出，但 email.mime 子包和 email.message 子模块不列出。

另请参阅 sys.builtin_module_names 列表。

Added in version 3.10.

sys. thread_info ¶

A 命名元组保持线程实现的有关信息。

thread_info. name ¶

The name of the thread implementation:

"nt" ：Windows 线程
"pthread" ：POSIX 线程
"pthread-stubs" ：stub POSIX 线程 (在不支持线程的 WebAssembly 平台)
"solaris" ：Solaris 线程

thread_info. lock ¶

The name of the lock implementation:

"semaphore" ：锁使用信号量
"mutex+cond" ：锁使用互斥和条件变量
None 如果此信息未知

thread_info. version ¶: The name and version of the thread library. It is a string, or None 若此信息未知。

Added in version 3.3.

sys. tracebacklimit ¶: 当设为整数值时，此变量确定打印回溯信息的最大级数，当发生未处理异常时。默认为 1000 。当设为 0 或更少，所有回溯信息被抑制且只打印异常类型和值。

sys. unraisablehook ( unraisable , / ) ¶

处理不可引发异常。

被调用当发生异常但 Python 没有办法处理它时。例如，当析构函数引发异常或在垃圾收集期间 ( gc.collect() ).

The unraisable 自变量拥有下列属性：

exc_type ：异常类型。
exc_value ：异常值，可以是 None .
exc_traceback ：异常回溯，可以是 None .
err_msg ：错误消息，可以是 None .
object ：导致异常的对象，可以是 None .

默认挂钩格式 err_msg and object as: f'{err_msg}: {object!r}' ；使用 "Exception ignored in" 错误消息若 err_msg is None .

sys.unraisablehook() 可以被覆盖以控制如何处理不可引发异常。

另请参阅

excepthook() 处理未捕获异常。

警告

存储 exc_value 使用自定义挂钩可以创建引用循环。应明确清零以中断引用循环，当不再需要异常时。

存储 object 使用自定义挂钩可以复活它，若它被设为正定稿对象。避免存储 object 在自定义挂钩完成后以避免复活对象。

引发审计事件 sys.unraisablehook 采用自变量 hook , unraisable 当出现无法处理的异常时。 unraisable 是传递给挂钩的同一对象。若没有设置挂钩， hook 可以是 None .

Added in version 3.8.

sys. version ¶: A string containing the version number of the Python interpreter plus additional information on the build number and compiler used. This string is displayed when the interactive interpreter is started. Do not extract version information out of it, rather, use version_info and the functions provided by the platform 模块。

sys. api_version ¶: The C API version for this interpreter. Programmers may find this useful when debugging version conflicts between Python and extension modules.

sys. version_info ¶

包含版本编号 5 分量的元组： major , minor , micro , releaselevel ，和 serial 。所有值除了 releaselevel 都是整数；releaselevel 为 'alpha' , 'beta' , 'candidate' ，或 'final' 。 version_info value corresponding to the Python version 2.0 is (2, 0, 0, 'final', 0) . The components can also be accessed by name, so sys.version_info[0] 相当于 sys.version_info.major 依此类推。

3.1 版改变：添加命名组件属性。

sys. warnoptions ¶: This is an implementation detail of the warnings framework; do not modify this value. Refer to the warnings module for more information on the warnings framework.

sys. winver ¶: The version number used to form registry keys on Windows platforms. This is stored as string resource 1000 in the Python DLL. The value is normally the major and minor versions of the running Python interpreter. It is provided in the sys module for informational purposes; modifying this value has no effect on the registry keys used by Python.

可用性：Windows。

sys. monitoring: Namespace containing functions and constants for register callbacks and controlling monitoring events. See sys.monitoring 了解细节。

sys. _xoptions ¶

各种特定实现标志的字典传递透过 -X 命令行选项。选项名要么映射到它们的值 (若明确给定)，要么映射到 True 。范例：

$ ./python -Xa=b -Xc
Python 3.2a3+ (py3k, Oct 16 2010, 20:14:50)
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys._xoptions
{'a': 'b', 'c': True}

CPython 实现细节： This is a CPython-specific way of accessing options passed through -X . Other implementations may export them through other means, or not at all.

Added in version 3.2.

引文

[ C99 ]

ISO/IEC 9899:1999. “Programming languages – C.” A public draft of this standard is available at https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf .

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