`sys` --- 系統特定的參數與函式¶

This module provides access to some variables used or maintained by the interpreter and to functions that interact strongly with the interpreter. It is always available. Unless explicitly noted otherwise, all variables are read-only.

sys.abiflags¶: On POSIX systems where Python was built with the standard configure script, this contains the ABI flags as specified by PEP 3149.

在 3.2 版被加入.

在 3.8 版的變更: Default flags became an empty string (m flag for pymalloc has been removed).

可用性: Unix.

sys.addaudithook(hook)¶

Append the callable hook to the list of active auditing hooks for the current (sub)interpreter.

When an auditing event is raised through the sys.audit() function, each hook will be called in the order it was added with the event name and the tuple of arguments. Native hooks added by PySys_AddAuditHook() are called first, followed by hooks added in the current (sub)interpreter. Hooks can then log the event, raise an exception to abort the operation, or terminate the process entirely.

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.

呼叫 sys.addaudithook() 本身會引發一個不帶任何引數、名為 sys.addaudithook 的稽核事件。如果任何現有的 hook 引發從 RuntimeError 衍生的例外，則不會添加新的 hook 並抑制異常。因此，除非呼叫者控制所有已存在的 hook，他們不能假設他們的 hook 已被添加。

所有會被 CPython 所引發的事件請參考稽核事件總表、設計相關討論請見 PEP 578。

在 3.8 版被加入.

在 3.8.1 版的變更: Exceptions derived from Exception but not RuntimeError are no longer suppressed.

CPython 實作細節： When tracing is enabled (see settrace()), Python hooks are only traced if the callable has a __cantrace__ member that is set to a true value. Otherwise, trace functions will skip the hook.

sys.argv¶

The list of command line arguments passed to a Python script. argv[0] is the script name (it is operating system dependent whether this is a full pathname or not). If the command was executed using the -c command line option to the interpreter, argv[0] is set to the string '-c'. If no script name was passed to the Python interpreter, argv[0] is the empty string.

To loop over the standard input, or the list of files given on the command line, see the fileinput module.

另請參閱 sys.orig_argv。

備註

On Unix, command line arguments are passed by bytes from OS. Python decodes them with filesystem encoding and "surrogateescape" error handler. When you need original bytes, you can get it by [os.fsencode(arg) for arg in sys.argv].

sys.audit(event, *args)¶

Raise an auditing event and trigger any active auditing hooks. event is a string identifying the event, and args may contain optional arguments with more information about the event. The number and types of arguments for a given event are considered a public and stable API and should not be modified between releases.

舉例來說，一個名為 os.chdir 的稽核事件擁有一個引數 path，其內容為所要求的新工作目錄。

sys.audit() will call the existing auditing hooks, passing the event name and arguments, and will re-raise the first exception from any hook. In general, if an exception is raised, it should not be handled and the process should be terminated as quickly as possible. This allows hook implementations to decide how to respond to particular events: they can merely log the event or abort the operation by raising an exception.

Hooks are added using the sys.addaudithook() or PySys_AddAuditHook() functions.

The native equivalent of this function is PySys_Audit(). Using the native function is preferred when possible.

所有會被 CPython 所引發的事件請參考稽核事件總表。

在 3.8 版被加入.

sys.base_exec_prefix¶

Equivalent to exec_prefix, but referring to the base Python installation.

When running under 虛擬環境, exec_prefix gets overwritten to the virtual environment prefix. base_exec_prefix, conversely, does not change, and always points to the base Python installation. Refer to 虛擬環境 for more information.

在 3.3 版被加入.

sys.base_prefix¶

Equivalent to prefix, but referring to the base Python installation.

When running under virtual environment, prefix gets overwritten to the virtual environment prefix. base_prefix, conversely, does not change, and always points to the base Python installation. Refer to 虛擬環境 for more information.

在 3.3 版被加入.

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¶

A tuple of strings containing the names of all modules that are compiled into this Python interpreter. (This information is not available in any other way --- modules.keys() only lists the imported modules.)

另請參閱 sys.stdlib_module_names 清單。

sys.call_tracing(func, args)¶

Call 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¶: A string containing the copyright pertaining to the Python interpreter.

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.

This function should be used for internal and specialized purposes only.

在 3.13 版之後被棄用: Use the more general _clear_internal_caches() function instead.

sys._clear_internal_caches()¶: Clear all internal performance-related caches. Use this function only to release unnecessary references and memory blocks when hunting for leaks.

在 3.13 版被加入.

sys._current_frames()¶

Return a dictionary mapping each thread's identifier to the topmost stack frame currently active in that thread at the time the function is called. Note that functions in the traceback module can build the call stack given such a frame.

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.

This function should be used for internal and specialized purposes only.

引發一個不附帶引數的稽核事件 sys._current_frames。

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.

This function should be used for internal and specialized purposes only.

引發一個不附帶引數的稽核事件 sys._current_exceptions。

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

sys.breakpointhook()¶

This hook function is called by built-in 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. In this case, 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() returns, sys.breakpointhook() returns to the built-in breakpoint() function.

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

Also note that if sys.breakpointhook() is overridden programmatically, PYTHONBREAKPOINT is not consulted.

在 3.7 版被加入.

sys._debugmallocstats()¶

Print low-level information to stderr about the state of CPython's memory allocator.

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

在 3.3 版被加入.

CPython 實作細節： This function is specific to CPython. The exact output format is not defined here, and may change.

sys.dllhandle¶: Integer specifying the handle of the Python DLL.

可用性: Windows.

sys.displayhook(value)¶

If value is not None, this function prints repr(value) to sys.stdout, and saves value in builtins._. If repr(value) is not encodable to sys.stdout.encoding with sys.stdout.errors error handler (which is probably 'strict'), encode it to sys.stdout.encoding with 'backslashreplace' error handler.

sys.displayhook is called on the result of evaluating an expression entered in an interactive Python session. The display of these values can be customized by assigning another one-argument function to sys.displayhook.

Pseudo-code:

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

在 3.2 版的變更: Use 'backslashreplace' error handler on

sys --- 系統特定的參數與函式¶

`sys` --- 系統特定的參數與函式¶