Command-line argument strings list: [command, arguments...]. Like C’s argv array.

Indicates the native byte-order (e.g., big for big-endian).

Tuple of string names of C modules compiled into this Python interpreter.

String containing the Python interpreter copyright.

Python DLL integer handle; Windows only (see the Python Library Reference).

Called by Python to display result values in interactive sessions; assign sys.displayhook to a one-argument function to customize output.

Called by Python to display uncaught exception details to stderr; assign sys.excepthook to a three-argument function to customize exception displays.

Returns tuple of three values describing the exception currently being handled (type, value, traceback), where type is the exception class, value is the instance of the exception class raised, and traceback is an object that gives access to the runtime call stack as it existed when the exception occurred. Specific to current thread. Subsumes exc_type, exc_value, and exc_traceback in Python 1.5 and later (all three of which are removed completely in Python 3.0). See the traceback module in the Python Library Reference for processing traceback objects, and The try Statement for more on exceptions.

Assign to a string giving the site-specific directory prefix where the platform-dependent Python files are installed; defaults to /usr/local or a build-time argument. Use this to locate shared library modules (in <exec_prefix>/lib/python<version>/lib-dynload) and configuration files.

String giving the full file pathname of the Python interpreter program running the caller.

Exits from a Python process with status N (default 0) by raising a SystemExit built-in exception (can be caught in a try statement and ignored). See also SystemExit (in Built-in Exceptions) and the os._exit() function (in The os System Module), which exits immediately without exception processing (useful in child processes after an os.fork()). Also see the atexit module for exit function specification.

Returns the interpreter’s “check interval”; see setcheckinterval, later in this list.

Returns the name of the current default string encoding used by the Unicode implementation.

Returns the name of the encoding used to convert Unicode filenames into system file names, or None if the system default encoding is used.

Returns object’s current reference count value (+1 for the call’s argument).

Returns the maximum depth limit of the Python call stack; see also setrecursionlimit, later in this list.

Returns the size of an object in bytes. The object can be any type of object. All built-in objects return correct results, but third-party extension results are implementation specific. default provides a value that will be returned if the object type does not implement the size retrieval interface.

Returns a frame object from the Python call stack (see the Python Library Reference).

Python version number, encoded as a single integer (viewed best with the hex() built-in function). Increases with each new release.

Enters string in the table of “interned” strings and returns the interned string—the string itself or a copy. Interning strings provides a small performance improvement for dictionary lookup: if both the keys in a dictionary and the lookup key are interned, key comparisons (after hashing) can be done by comparing pointers instead of strings. Normally, names used in Python programs are automatically interned, and the dictionaries used to hold module, class, and instance attributes have interned keys.

Type, value, and traceback objects of last uncaught exception (mostly for postmortem debugging).

An integer giving the maximum value a variable of type Py_ssize_t can take. It’s usually 2**31 − 1 on a 32-bit platform and 2**63 − 1 on a 64-bit platform.

An integer giving the largest supported code point for a Unicode character. The value of this depends on the configuration option that specifies whether Unicode characters are stored as UCS-2 or UCS-4.

Dictionary of modules that are already loaded; there is one name:object entry per module. Writable (for example, del sys.modules['name'] forces a module to be reloaded on next import).

List of strings specifying module import search path. Initialized from PYTHONPATH shell variable, .pth path files, and any installation-dependent defaults. Writable (e.g., sys.path.append('C:\dir') adds a directory to the search path within a script).

The first item, path[0], is the directory containing the script that was used to invoke the Python interpreter. If the script directory is not available (e.g., if the interpreter is invoked interactively or if the script is read from standard input), path[0] is the empty string, which directs Python to search modules in the current working directory first. The script directory is inserted before the entries inserted from PYTHONPATH.

String identifying the system on which Python is running: e.g., 'sunos5', 'darwin', 'linux2', 'win32', 'cygwin', 'PalmOS3'. Useful for tests in platform-dependent code. Hint: 'win32' means all current flavors of Windows, or test as sys.platform[:3]=='win' or sys.platform.startswith('win').

Assign to a string giving the site-specific directory prefix, where platform-independent Python files are installed; defaults to /usr/local or a build-time argument. Python library modules are installed in the directory <prefix>/lib/python<version>; platform-independent header files are stored in <prefix>/include/python<version>.

String specifying primary prompt in interactive mode; defaults to >>> unless assigned.

String specifying secondary prompt for compound statement continuations, in interactive mode; defaults to ... unless assigned.

If this is true, Python won’t try to write “.pyc” or “.pyo” files on the import of source modules (see also “-B” command-line option).

Call to set how often the interpreter checks for periodic tasks (e.g., thread switches, signal handlers) to reps. Measured in virtual machine instructions (default is 100). In general, a Python statement translates to multiple virtual machine instructions. Lower values maximize thread responsiveness but also maximize thread switch overhead.

Call to set the current default string encoding used by the Unicode implementation. Intended for use by the site module and is available during start-up only.

Call to set the system profile function to func: the profiler’s “hook” (not run for each line). See the Python Library Reference for details.

Call to set maximum depth of the Python call stack to depth. This limit prevents infinite recursion from causing an overflow of the C stack and crashing Python. The default is 1,000 on Windows, but this may vary.

Call to set the system trace function to func: the program location or state change callback “hook” used by debuggers, etc. See the Python Library Reference for details.

Standard input stream: a preopened file object. Can be assigned to any object with read methods to reset input within a script (e.g., sys.stdin=MyObj()). Used for interpreter input, including the input() built-in function (and raw_input() in Python 2).

Standard output stream: a preopened file object. Can be assigned to any object with write methods to reset output within a script (e.g., sys.stdout=open('log', 'a')). Used for some prompts and the print() built-in function (and print statement in Python 2).

Standard error stream: a preopened file object. Can be assigned to any object with write methods to reset stderr within a script (e.g., sys.stderr=wrappedsocket). Used for interpreter prompts/errors.

Original values of stdin, stderr, and stdout at program start (e.g., for restores as a last resort; normally, when assigning to sys.stdout, etc., save the old value and restore it in a finally clause). Can be None for GUI apps on Windows with no console.

Maximum number of traceback levels to print on uncaught exceptions; defaults to 1,000 unless assigned.

String containing the version number of the Python interpreter.

Tuple containing five version identification components: major, minor, micro, release level, and serial. For Python 3.0.1, this is (3, 0, 1, 'final', 0) (see the Python Library Reference).

Version number used to form registry keys on Windows platforms (available only on Windows; see the Python Library Reference).