Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1 | :mod:`sys` --- System-specific parameters and functions |
| 2 | ======================================================= |
| 3 | |
| 4 | .. module:: sys |
| 5 | :synopsis: Access system-specific parameters and functions. |
| 6 | |
Terry Jan Reedy | fa089b9 | 2016-06-11 15:02:54 -0400 | [diff] [blame] | 7 | -------------- |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 8 | |
| 9 | This module provides access to some variables used or maintained by the |
| 10 | interpreter and to functions that interact strongly with the interpreter. It is |
| 11 | always available. |
| 12 | |
| 13 | |
Barry Warsaw | a40453d | 2010-10-16 14:17:50 +0000 | [diff] [blame] | 14 | .. data:: abiflags |
| 15 | |
Georg Brandl | df48b97 | 2014-03-24 09:06:18 +0100 | [diff] [blame] | 16 | On POSIX systems where Python was built with the standard ``configure`` |
Barry Warsaw | a40453d | 2010-10-16 14:17:50 +0000 | [diff] [blame] | 17 | script, this contains the ABI flags as specified by :pep:`3149`. |
| 18 | |
Victor Stinner | 7efc526 | 2019-06-15 03:24:41 +0200 | [diff] [blame] | 19 | .. versionchanged:: 3.8 |
| 20 | Default flags became an empty string (``m`` flag for pymalloc has been |
| 21 | removed). |
| 22 | |
Barry Warsaw | a40453d | 2010-10-16 14:17:50 +0000 | [diff] [blame] | 23 | .. versionadded:: 3.2 |
| 24 | |
Georg Brandl | df48b97 | 2014-03-24 09:06:18 +0100 | [diff] [blame] | 25 | |
Steve Dower | b82e17e | 2019-05-23 08:45:22 -0700 | [diff] [blame] | 26 | .. function:: addaudithook(hook) |
| 27 | |
| 28 | Adds the callable *hook* to the collection of active auditing hooks for the |
| 29 | current interpreter. |
| 30 | |
| 31 | When an auditing event is raised through the :func:`sys.audit` function, each |
| 32 | hook will be called in the order it was added with the event name and the |
| 33 | tuple of arguments. Native hooks added by :c:func:`PySys_AddAuditHook` are |
| 34 | called first, followed by hooks added in the current interpreter. |
| 35 | |
| 36 | Calling this function will trigger an event for all existing hooks, and if |
| 37 | any raise an exception derived from :class:`Exception`, the add will be |
| 38 | silently ignored. As a result, callers cannot assume that their hook has been |
| 39 | added unless they control all existing hooks. |
| 40 | |
| 41 | .. versionadded:: 3.8 |
| 42 | |
| 43 | .. impl-detail:: |
| 44 | |
| 45 | When tracing is enabled, Python hooks are only traced if the callable has |
| 46 | a ``__cantrace__`` member that is set to a true value. Otherwise, trace |
| 47 | functions will not see the hook. |
| 48 | |
| 49 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 50 | .. data:: argv |
| 51 | |
| 52 | The list of command line arguments passed to a Python script. ``argv[0]`` is the |
| 53 | script name (it is operating system dependent whether this is a full pathname or |
| 54 | not). If the command was executed using the :option:`-c` command line option to |
| 55 | the interpreter, ``argv[0]`` is set to the string ``'-c'``. If no script name |
| 56 | was passed to the Python interpreter, ``argv[0]`` is the empty string. |
| 57 | |
| 58 | To loop over the standard input, or the list of files given on the |
| 59 | command line, see the :mod:`fileinput` module. |
| 60 | |
Inada Naoki | 38f4e46 | 2019-03-30 14:32:08 +0900 | [diff] [blame] | 61 | .. note:: |
| 62 | On Unix, command line arguments are passed by bytes from OS. Python decodes |
| 63 | them with filesystem encoding and "surrogateescape" error handler. |
| 64 | When you need original bytes, you can get it by |
| 65 | ``[os.fsencode(arg) for arg in sys.argv]``. |
| 66 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 67 | |
Steve Dower | b82e17e | 2019-05-23 08:45:22 -0700 | [diff] [blame] | 68 | .. _auditing: |
| 69 | |
| 70 | .. function:: audit(event, *args) |
| 71 | |
| 72 | .. index:: single: auditing |
| 73 | |
| 74 | Raises an auditing event with any active hooks. The event name is a string |
| 75 | identifying the event and its associated schema, which is the number and |
| 76 | types of arguments. The schema for a given event is considered public and |
| 77 | stable API and should not be modified between releases. |
| 78 | |
| 79 | This function will raise the first exception raised by any hook. In general, |
| 80 | these errors should not be handled and should terminate the process as |
| 81 | quickly as possible. |
| 82 | |
| 83 | Hooks are added using the :func:`sys.addaudithook` or |
| 84 | :c:func:`PySys_AddAuditHook` functions. |
| 85 | |
| 86 | The native equivalent of this function is :c:func:`PySys_Audit`. Using the |
| 87 | native function is preferred when possible. |
| 88 | |
| 89 | .. versionadded:: 3.8 |
| 90 | |
| 91 | |
Vinay Sajip | 7ded1f0 | 2012-05-26 03:45:29 +0100 | [diff] [blame] | 92 | .. data:: base_exec_prefix |
| 93 | |
| 94 | Set during Python startup, before ``site.py`` is run, to the same value as |
Vinay Sajip | cd9b746 | 2012-07-09 10:37:01 +0100 | [diff] [blame] | 95 | :data:`exec_prefix`. If not running in a |
| 96 | :ref:`virtual environment <venv-def>`, the values will stay the same; if |
| 97 | ``site.py`` finds that a virtual environment is in use, the values of |
| 98 | :data:`prefix` and :data:`exec_prefix` will be changed to point to the |
| 99 | virtual environment, whereas :data:`base_prefix` and |
Vinay Sajip | 7ded1f0 | 2012-05-26 03:45:29 +0100 | [diff] [blame] | 100 | :data:`base_exec_prefix` will remain pointing to the base Python |
| 101 | installation (the one which the virtual environment was created from). |
| 102 | |
Georg Brandl | 039b01d | 2012-05-26 09:11:22 +0200 | [diff] [blame] | 103 | .. versionadded:: 3.3 |
| 104 | |
| 105 | |
Vinay Sajip | 7ded1f0 | 2012-05-26 03:45:29 +0100 | [diff] [blame] | 106 | .. data:: base_prefix |
| 107 | |
| 108 | Set during Python startup, before ``site.py`` is run, to the same value as |
Vinay Sajip | cd9b746 | 2012-07-09 10:37:01 +0100 | [diff] [blame] | 109 | :data:`prefix`. If not running in a :ref:`virtual environment <venv-def>`, the values |
Vinay Sajip | 7ded1f0 | 2012-05-26 03:45:29 +0100 | [diff] [blame] | 110 | will stay the same; if ``site.py`` finds that a virtual environment is in |
| 111 | use, the values of :data:`prefix` and :data:`exec_prefix` will be changed to |
| 112 | point to the virtual environment, whereas :data:`base_prefix` and |
| 113 | :data:`base_exec_prefix` will remain pointing to the base Python |
| 114 | installation (the one which the virtual environment was created from). |
| 115 | |
Georg Brandl | 039b01d | 2012-05-26 09:11:22 +0200 | [diff] [blame] | 116 | .. versionadded:: 3.3 |
| 117 | |
| 118 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 119 | .. data:: byteorder |
| 120 | |
| 121 | An indicator of the native byte order. This will have the value ``'big'`` on |
| 122 | big-endian (most-significant byte first) platforms, and ``'little'`` on |
| 123 | little-endian (least-significant byte first) platforms. |
| 124 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 125 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 126 | .. data:: builtin_module_names |
| 127 | |
| 128 | A tuple of strings giving the names of all modules that are compiled into this |
| 129 | Python interpreter. (This information is not available in any other way --- |
| 130 | ``modules.keys()`` only lists the imported modules.) |
| 131 | |
| 132 | |
Georg Brandl | 8527126 | 2010-10-17 11:06:14 +0000 | [diff] [blame] | 133 | .. function:: call_tracing(func, args) |
| 134 | |
| 135 | Call ``func(*args)``, while tracing is enabled. The tracing state is saved, |
| 136 | and restored afterwards. This is intended to be called from a debugger from |
| 137 | a checkpoint, to recursively debug some other code. |
| 138 | |
| 139 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 140 | .. data:: copyright |
| 141 | |
| 142 | A string containing the copyright pertaining to the Python interpreter. |
| 143 | |
| 144 | |
Christian Heimes | 15ebc88 | 2008-02-04 18:48:49 +0000 | [diff] [blame] | 145 | .. function:: _clear_type_cache() |
| 146 | |
| 147 | Clear the internal type cache. The type cache is used to speed up attribute |
| 148 | and method lookups. Use the function *only* to drop unnecessary references |
| 149 | during reference leak debugging. |
| 150 | |
| 151 | This function should be used for internal and specialized purposes only. |
Christian Heimes | 2685563 | 2008-01-27 23:50:43 +0000 | [diff] [blame] | 152 | |
Christian Heimes | 2685563 | 2008-01-27 23:50:43 +0000 | [diff] [blame] | 153 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 154 | .. function:: _current_frames() |
| 155 | |
| 156 | Return a dictionary mapping each thread's identifier to the topmost stack frame |
| 157 | currently active in that thread at the time the function is called. Note that |
| 158 | functions in the :mod:`traceback` module can build the call stack given such a |
| 159 | frame. |
| 160 | |
| 161 | This is most useful for debugging deadlock: this function does not require the |
| 162 | deadlocked threads' cooperation, and such threads' call stacks are frozen for as |
| 163 | long as they remain deadlocked. The frame returned for a non-deadlocked thread |
| 164 | may bear no relationship to that thread's current activity by the time calling |
| 165 | code examines the frame. |
| 166 | |
| 167 | This function should be used for internal and specialized purposes only. |
| 168 | |
Steve Dower | b82e17e | 2019-05-23 08:45:22 -0700 | [diff] [blame] | 169 | .. audit-event:: sys._current_frames |
| 170 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 171 | |
Barry Warsaw | 36c1d1f | 2017-10-05 12:11:18 -0400 | [diff] [blame] | 172 | .. function:: breakpointhook() |
| 173 | |
| 174 | This hook function is called by built-in :func:`breakpoint`. By default, |
| 175 | it drops you into the :mod:`pdb` debugger, but it can be set to any other |
| 176 | function so that you can choose which debugger gets used. |
| 177 | |
| 178 | The signature of this function is dependent on what it calls. For example, |
| 179 | the default binding (e.g. ``pdb.set_trace()``) expects no arguments, but |
| 180 | you might bind it to a function that expects additional arguments |
| 181 | (positional and/or keyword). The built-in ``breakpoint()`` function passes |
| 182 | its ``*args`` and ``**kws`` straight through. Whatever |
| 183 | ``breakpointhooks()`` returns is returned from ``breakpoint()``. |
| 184 | |
| 185 | The default implementation first consults the environment variable |
| 186 | :envvar:`PYTHONBREAKPOINT`. If that is set to ``"0"`` then this function |
| 187 | returns immediately; i.e. it is a no-op. If the environment variable is |
| 188 | not set, or is set to the empty string, ``pdb.set_trace()`` is called. |
| 189 | Otherwise this variable should name a function to run, using Python's |
| 190 | dotted-import nomenclature, e.g. ``package.subpackage.module.function``. |
| 191 | In this case, ``package.subpackage.module`` would be imported and the |
| 192 | resulting module must have a callable named ``function()``. This is run, |
| 193 | passing in ``*args`` and ``**kws``, and whatever ``function()`` returns, |
| 194 | ``sys.breakpointhook()`` returns to the built-in :func:`breakpoint` |
| 195 | function. |
| 196 | |
| 197 | Note that if anything goes wrong while importing the callable named by |
| 198 | :envvar:`PYTHONBREAKPOINT`, a :exc:`RuntimeWarning` is reported and the |
| 199 | breakpoint is ignored. |
| 200 | |
| 201 | Also note that if ``sys.breakpointhook()`` is overridden programmatically, |
| 202 | :envvar:`PYTHONBREAKPOINT` is *not* consulted. |
| 203 | |
| 204 | .. versionadded:: 3.7 |
| 205 | |
David Malcolm | 49526f4 | 2012-06-22 14:55:41 -0400 | [diff] [blame] | 206 | .. function:: _debugmallocstats() |
| 207 | |
| 208 | Print low-level information to stderr about the state of CPython's memory |
| 209 | allocator. |
| 210 | |
| 211 | If Python is configured --with-pydebug, it also performs some expensive |
| 212 | internal consistency checks. |
| 213 | |
| 214 | .. versionadded:: 3.3 |
| 215 | |
| 216 | .. impl-detail:: |
| 217 | |
| 218 | This function is specific to CPython. The exact output format is not |
| 219 | defined here, and may change. |
| 220 | |
| 221 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 222 | .. data:: dllhandle |
| 223 | |
Cheryl Sabella | 2d6097d | 2018-10-12 10:55:20 -0400 | [diff] [blame] | 224 | Integer specifying the handle of the Python DLL. |
| 225 | |
| 226 | .. availability:: Windows. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 227 | |
| 228 | |
| 229 | .. function:: displayhook(value) |
| 230 | |
Victor Stinner | 13d49ee | 2010-12-04 17:24:33 +0000 | [diff] [blame] | 231 | If *value* is not ``None``, this function prints ``repr(value)`` to |
| 232 | ``sys.stdout``, and saves *value* in ``builtins._``. If ``repr(value)`` is |
| 233 | not encodable to ``sys.stdout.encoding`` with ``sys.stdout.errors`` error |
| 234 | handler (which is probably ``'strict'``), encode it to |
| 235 | ``sys.stdout.encoding`` with ``'backslashreplace'`` error handler. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 236 | |
Christian Heimes | d8654cf | 2007-12-02 15:22:16 +0000 | [diff] [blame] | 237 | ``sys.displayhook`` is called on the result of evaluating an :term:`expression` |
| 238 | entered in an interactive Python session. The display of these values can be |
| 239 | customized by assigning another one-argument function to ``sys.displayhook``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 240 | |
Victor Stinner | 13d49ee | 2010-12-04 17:24:33 +0000 | [diff] [blame] | 241 | Pseudo-code:: |
| 242 | |
| 243 | def displayhook(value): |
| 244 | if value is None: |
| 245 | return |
| 246 | # Set '_' to None to avoid recursion |
| 247 | builtins._ = None |
| 248 | text = repr(value) |
| 249 | try: |
| 250 | sys.stdout.write(text) |
| 251 | except UnicodeEncodeError: |
| 252 | bytes = text.encode(sys.stdout.encoding, 'backslashreplace') |
| 253 | if hasattr(sys.stdout, 'buffer'): |
| 254 | sys.stdout.buffer.write(bytes) |
| 255 | else: |
| 256 | text = bytes.decode(sys.stdout.encoding, 'strict') |
| 257 | sys.stdout.write(text) |
| 258 | sys.stdout.write("\n") |
| 259 | builtins._ = value |
| 260 | |
| 261 | .. versionchanged:: 3.2 |
| 262 | Use ``'backslashreplace'`` error handler on :exc:`UnicodeEncodeError`. |
| 263 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 264 | |
Éric Araujo | da27263 | 2011-10-05 01:17:38 +0200 | [diff] [blame] | 265 | .. data:: dont_write_bytecode |
| 266 | |
Brett Cannon | f299abd | 2015-04-13 14:21:02 -0400 | [diff] [blame] | 267 | If this is true, Python won't try to write ``.pyc`` files on the |
Éric Araujo | da27263 | 2011-10-05 01:17:38 +0200 | [diff] [blame] | 268 | import of source modules. This value is initially set to ``True`` or |
| 269 | ``False`` depending on the :option:`-B` command line option and the |
| 270 | :envvar:`PYTHONDONTWRITEBYTECODE` environment variable, but you can set it |
| 271 | yourself to control bytecode file generation. |
| 272 | |
| 273 | |
Carl Meyer | b193fa9 | 2018-06-15 22:40:56 -0600 | [diff] [blame] | 274 | .. data:: pycache_prefix |
| 275 | |
| 276 | If this is set (not ``None``), Python will write bytecode-cache ``.pyc`` |
| 277 | files to (and read them from) a parallel directory tree rooted at this |
| 278 | directory, rather than from ``__pycache__`` directories in the source code |
| 279 | tree. Any ``__pycache__`` directories in the source code tree will be ignored |
| 280 | and new `.pyc` files written within the pycache prefix. Thus if you use |
| 281 | :mod:`compileall` as a pre-build step, you must ensure you run it with the |
| 282 | same pycache prefix (if any) that you will use at runtime. |
| 283 | |
| 284 | A relative path is interpreted relative to the current working directory. |
| 285 | |
| 286 | This value is initially set based on the value of the :option:`-X` |
| 287 | ``pycache_prefix=PATH`` command-line option or the |
| 288 | :envvar:`PYTHONPYCACHEPREFIX` environment variable (command-line takes |
| 289 | precedence). If neither are set, it is ``None``. |
| 290 | |
| 291 | .. versionadded:: 3.8 |
| 292 | |
| 293 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 294 | .. function:: excepthook(type, value, traceback) |
| 295 | |
| 296 | This function prints out a given traceback and exception to ``sys.stderr``. |
| 297 | |
| 298 | When an exception is raised and uncaught, the interpreter calls |
| 299 | ``sys.excepthook`` with three arguments, the exception class, exception |
| 300 | instance, and a traceback object. In an interactive session this happens just |
| 301 | before control is returned to the prompt; in a Python program this happens just |
| 302 | before the program exits. The handling of such top-level exceptions can be |
| 303 | customized by assigning another three-argument function to ``sys.excepthook``. |
| 304 | |
Victor Stinner | cd590a7 | 2019-05-28 00:39:52 +0200 | [diff] [blame] | 305 | .. seealso:: |
| 306 | |
| 307 | The :func:`sys.unraisablehook` function handles unraisable exceptions |
| 308 | and the :func:`threading.excepthook` function handles exception raised |
| 309 | by :func:`threading.Thread.run`. |
Victor Stinner | ef9d9b6 | 2019-05-22 11:28:22 +0200 | [diff] [blame] | 310 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 311 | |
Barry Warsaw | 36c1d1f | 2017-10-05 12:11:18 -0400 | [diff] [blame] | 312 | .. data:: __breakpointhook__ |
| 313 | __displayhook__ |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 314 | __excepthook__ |
Victor Stinner | ef9d9b6 | 2019-05-22 11:28:22 +0200 | [diff] [blame] | 315 | __unraisablehook__ |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 316 | |
Barry Warsaw | 36c1d1f | 2017-10-05 12:11:18 -0400 | [diff] [blame] | 317 | These objects contain the original values of ``breakpointhook``, |
Victor Stinner | ef9d9b6 | 2019-05-22 11:28:22 +0200 | [diff] [blame] | 318 | ``displayhook``, ``excepthook``, and ``unraisablehook`` at the start of the |
| 319 | program. They are saved so that ``breakpointhook``, ``displayhook`` and |
| 320 | ``excepthook``, ``unraisablehook`` can be restored in case they happen to |
| 321 | get replaced with broken or alternative objects. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 322 | |
Barry Warsaw | 36c1d1f | 2017-10-05 12:11:18 -0400 | [diff] [blame] | 323 | .. versionadded:: 3.7 |
| 324 | __breakpointhook__ |
| 325 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 326 | |
| 327 | .. function:: exc_info() |
| 328 | |
| 329 | This function returns a tuple of three values that give information about the |
| 330 | exception that is currently being handled. The information returned is specific |
| 331 | both to the current thread and to the current stack frame. If the current stack |
| 332 | frame is not handling an exception, the information is taken from the calling |
| 333 | stack frame, or its caller, and so on until a stack frame is found that is |
| 334 | handling an exception. Here, "handling an exception" is defined as "executing |
Benjamin Peterson | eec3d71 | 2008-06-11 15:59:43 +0000 | [diff] [blame] | 335 | an except clause." For any stack frame, only information about the exception |
| 336 | being currently handled is accessible. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 337 | |
| 338 | .. index:: object: traceback |
| 339 | |
Georg Brandl | 482b151 | 2010-03-21 09:02:59 +0000 | [diff] [blame] | 340 | If no exception is being handled anywhere on the stack, a tuple containing |
| 341 | three ``None`` values is returned. Otherwise, the values returned are |
| 342 | ``(type, value, traceback)``. Their meaning is: *type* gets the type of the |
| 343 | exception being handled (a subclass of :exc:`BaseException`); *value* gets |
| 344 | the exception instance (an instance of the exception type); *traceback* gets |
| 345 | a traceback object (see the Reference Manual) which encapsulates the call |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 346 | stack at the point where the exception originally occurred. |
| 347 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 348 | |
| 349 | .. data:: exec_prefix |
| 350 | |
| 351 | A string giving the site-specific directory prefix where the platform-dependent |
| 352 | Python files are installed; by default, this is also ``'/usr/local'``. This can |
Éric Araujo | 713d303 | 2010-11-18 16:38:46 +0000 | [diff] [blame] | 353 | be set at build time with the ``--exec-prefix`` argument to the |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 354 | :program:`configure` script. Specifically, all configuration files (e.g. the |
Éric Araujo | 58a9153 | 2011-10-05 01:28:24 +0200 | [diff] [blame] | 355 | :file:`pyconfig.h` header file) are installed in the directory |
Georg Brandl | eb25fb7 | 2012-02-23 21:12:39 +0100 | [diff] [blame] | 356 | :file:`{exec_prefix}/lib/python{X.Y}/config`, and shared library modules are |
Éric Araujo | 58a9153 | 2011-10-05 01:28:24 +0200 | [diff] [blame] | 357 | installed in :file:`{exec_prefix}/lib/python{X.Y}/lib-dynload`, where *X.Y* |
| 358 | is the version number of Python, for example ``3.2``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 359 | |
Larry Hastings | 3732ed2 | 2014-03-15 21:13:56 -0700 | [diff] [blame] | 360 | .. note:: |
| 361 | |
| 362 | If a :ref:`virtual environment <venv-def>` is in effect, this |
Vinay Sajip | cd9b746 | 2012-07-09 10:37:01 +0100 | [diff] [blame] | 363 | value will be changed in ``site.py`` to point to the virtual environment. |
| 364 | The value for the Python installation will still be available, via |
| 365 | :data:`base_exec_prefix`. |
Vinay Sajip | 7ded1f0 | 2012-05-26 03:45:29 +0100 | [diff] [blame] | 366 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 367 | |
| 368 | .. data:: executable |
| 369 | |
Petri Lehtinen | 9713321 | 2012-02-02 20:59:48 +0200 | [diff] [blame] | 370 | A string giving the absolute path of the executable binary for the Python |
| 371 | interpreter, on systems where this makes sense. If Python is unable to retrieve |
| 372 | the real path to its executable, :data:`sys.executable` will be an empty string |
| 373 | or ``None``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 374 | |
| 375 | |
| 376 | .. function:: exit([arg]) |
| 377 | |
| 378 | Exit from Python. This is implemented by raising the :exc:`SystemExit` |
| 379 | exception, so cleanup actions specified by finally clauses of :keyword:`try` |
Georg Brandl | 6f4e68d | 2010-10-17 10:51:45 +0000 | [diff] [blame] | 380 | statements are honored, and it is possible to intercept the exit attempt at |
| 381 | an outer level. |
| 382 | |
| 383 | The optional argument *arg* can be an integer giving the exit status |
| 384 | (defaulting to zero), or another type of object. If it is an integer, zero |
| 385 | is considered "successful termination" and any nonzero value is considered |
| 386 | "abnormal termination" by shells and the like. Most systems require it to be |
Martin Panter | b4ce1fc | 2015-11-30 03:18:29 +0000 | [diff] [blame] | 387 | in the range 0--127, and produce undefined results otherwise. Some systems |
Georg Brandl | 6f4e68d | 2010-10-17 10:51:45 +0000 | [diff] [blame] | 388 | have a convention for assigning specific meanings to specific exit codes, but |
| 389 | these are generally underdeveloped; Unix programs generally use 2 for command |
| 390 | line syntax errors and 1 for all other kind of errors. If another type of |
| 391 | object is passed, ``None`` is equivalent to passing zero, and any other |
| 392 | object is printed to :data:`stderr` and results in an exit code of 1. In |
| 393 | particular, ``sys.exit("some error message")`` is a quick way to exit a |
| 394 | program when an error occurs. |
| 395 | |
| 396 | Since :func:`exit` ultimately "only" raises an exception, it will only exit |
| 397 | the process when called from the main thread, and the exception is not |
| 398 | intercepted. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 399 | |
Martin Panter | b4ce1fc | 2015-11-30 03:18:29 +0000 | [diff] [blame] | 400 | .. versionchanged:: 3.6 |
| 401 | If an error occurs in the cleanup after the Python interpreter |
| 402 | has caught :exc:`SystemExit` (such as an error flushing buffered data |
| 403 | in the standard streams), the exit status is changed to 120. |
| 404 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 405 | |
Christian Heimes | d32ed6f | 2008-01-14 18:49:24 +0000 | [diff] [blame] | 406 | .. data:: flags |
| 407 | |
Benjamin Peterson | 2b8ef2d | 2011-04-20 18:31:22 -0500 | [diff] [blame] | 408 | The :term:`struct sequence` *flags* exposes the status of command line |
| 409 | flags. The attributes are read only. |
Christian Heimes | d32ed6f | 2008-01-14 18:49:24 +0000 | [diff] [blame] | 410 | |
Éric Araujo | 5ab4776 | 2011-03-26 00:47:04 +0100 | [diff] [blame] | 411 | ============================= ============================= |
| 412 | attribute flag |
| 413 | ============================= ============================= |
| 414 | :const:`debug` :option:`-d` |
Éric Araujo | 5ab4776 | 2011-03-26 00:47:04 +0100 | [diff] [blame] | 415 | :const:`inspect` :option:`-i` |
| 416 | :const:`interactive` :option:`-i` |
Danish Prakash | 656d52d | 2018-10-07 16:12:31 +0000 | [diff] [blame] | 417 | :const:`isolated` :option:`-I` |
Éric Araujo | 5ab4776 | 2011-03-26 00:47:04 +0100 | [diff] [blame] | 418 | :const:`optimize` :option:`-O` or :option:`-OO` |
| 419 | :const:`dont_write_bytecode` :option:`-B` |
| 420 | :const:`no_user_site` :option:`-s` |
| 421 | :const:`no_site` :option:`-S` |
| 422 | :const:`ignore_environment` :option:`-E` |
| 423 | :const:`verbose` :option:`-v` |
| 424 | :const:`bytes_warning` :option:`-b` |
Éric Araujo | 722bec4 | 2011-03-26 01:59:47 +0100 | [diff] [blame] | 425 | :const:`quiet` :option:`-q` |
Georg Brandl | 2daf6ae | 2012-02-20 19:54:16 +0100 | [diff] [blame] | 426 | :const:`hash_randomization` :option:`-R` |
Victor Stinner | 5e3806f | 2017-11-30 11:40:24 +0100 | [diff] [blame] | 427 | :const:`dev_mode` :option:`-X` ``dev`` |
Victor Stinner | 91106cd | 2017-12-13 12:29:09 +0100 | [diff] [blame] | 428 | :const:`utf8_mode` :option:`-X` ``utf8`` |
Éric Araujo | 5ab4776 | 2011-03-26 00:47:04 +0100 | [diff] [blame] | 429 | ============================= ============================= |
Georg Brandl | 8aa7e99 | 2010-12-28 18:30:18 +0000 | [diff] [blame] | 430 | |
| 431 | .. versionchanged:: 3.2 |
| 432 | Added ``quiet`` attribute for the new :option:`-q` flag. |
Christian Heimes | d32ed6f | 2008-01-14 18:49:24 +0000 | [diff] [blame] | 433 | |
Georg Brandl | 09a7c72 | 2012-02-20 21:31:46 +0100 | [diff] [blame] | 434 | .. versionadded:: 3.2.3 |
Georg Brandl | 2daf6ae | 2012-02-20 19:54:16 +0100 | [diff] [blame] | 435 | The ``hash_randomization`` attribute. |
| 436 | |
Éric Araujo | 3e89870 | 2011-04-24 04:37:00 +0200 | [diff] [blame] | 437 | .. versionchanged:: 3.3 |
| 438 | Removed obsolete ``division_warning`` attribute. |
| 439 | |
Danish Prakash | 656d52d | 2018-10-07 16:12:31 +0000 | [diff] [blame] | 440 | .. versionchanged:: 3.4 |
| 441 | Added ``isolated`` attribute for :option:`-I` ``isolated`` flag. |
| 442 | |
Victor Stinner | 5e3806f | 2017-11-30 11:40:24 +0100 | [diff] [blame] | 443 | .. versionchanged:: 3.7 |
Victor Stinner | 91106cd | 2017-12-13 12:29:09 +0100 | [diff] [blame] | 444 | Added ``dev_mode`` attribute for the new :option:`-X` ``dev`` flag |
| 445 | and ``utf8_mode`` attribute for the new :option:`-X` ``utf8`` flag. |
Victor Stinner | 5e3806f | 2017-11-30 11:40:24 +0100 | [diff] [blame] | 446 | |
Christian Heimes | d32ed6f | 2008-01-14 18:49:24 +0000 | [diff] [blame] | 447 | |
Christian Heimes | 9385266 | 2007-12-01 12:22:32 +0000 | [diff] [blame] | 448 | .. data:: float_info |
| 449 | |
Benjamin Peterson | 2b8ef2d | 2011-04-20 18:31:22 -0500 | [diff] [blame] | 450 | A :term:`struct sequence` holding information about the float type. It |
| 451 | contains low level information about the precision and internal |
| 452 | representation. The values correspond to the various floating-point |
| 453 | constants defined in the standard header file :file:`float.h` for the 'C' |
| 454 | programming language; see section 5.2.4.2.2 of the 1999 ISO/IEC C standard |
| 455 | [C99]_, 'Characteristics of floating types', for details. |
Christian Heimes | 9385266 | 2007-12-01 12:22:32 +0000 | [diff] [blame] | 456 | |
Georg Brandl | 44ea77b | 2013-03-28 13:28:44 +0100 | [diff] [blame] | 457 | .. tabularcolumns:: |l|l|L| |
| 458 | |
Mark Dickinson | be5846b | 2010-07-02 20:26:07 +0000 | [diff] [blame] | 459 | +---------------------+----------------+--------------------------------------------------+ |
| 460 | | attribute | float.h macro | explanation | |
| 461 | +=====================+================+==================================================+ |
Mark Dickinson | 39af05f | 2010-07-03 09:17:16 +0000 | [diff] [blame] | 462 | | :const:`epsilon` | DBL_EPSILON | difference between 1 and the least value greater | |
Mark Dickinson | be5846b | 2010-07-02 20:26:07 +0000 | [diff] [blame] | 463 | | | | than 1 that is representable as a float | |
| 464 | +---------------------+----------------+--------------------------------------------------+ |
| 465 | | :const:`dig` | DBL_DIG | maximum number of decimal digits that can be | |
| 466 | | | | faithfully represented in a float; see below | |
| 467 | +---------------------+----------------+--------------------------------------------------+ |
| 468 | | :const:`mant_dig` | DBL_MANT_DIG | float precision: the number of base-``radix`` | |
| 469 | | | | digits in the significand of a float | |
| 470 | +---------------------+----------------+--------------------------------------------------+ |
| 471 | | :const:`max` | DBL_MAX | maximum representable finite float | |
| 472 | +---------------------+----------------+--------------------------------------------------+ |
| 473 | | :const:`max_exp` | DBL_MAX_EXP | maximum integer e such that ``radix**(e-1)`` is | |
| 474 | | | | a representable finite float | |
| 475 | +---------------------+----------------+--------------------------------------------------+ |
| 476 | | :const:`max_10_exp` | DBL_MAX_10_EXP | maximum integer e such that ``10**e`` is in the | |
| 477 | | | | range of representable finite floats | |
| 478 | +---------------------+----------------+--------------------------------------------------+ |
| 479 | | :const:`min` | DBL_MIN | minimum positive normalized float | |
| 480 | +---------------------+----------------+--------------------------------------------------+ |
| 481 | | :const:`min_exp` | DBL_MIN_EXP | minimum integer e such that ``radix**(e-1)`` is | |
| 482 | | | | a normalized float | |
| 483 | +---------------------+----------------+--------------------------------------------------+ |
| 484 | | :const:`min_10_exp` | DBL_MIN_10_EXP | minimum integer e such that ``10**e`` is a | |
| 485 | | | | normalized float | |
| 486 | +---------------------+----------------+--------------------------------------------------+ |
| 487 | | :const:`radix` | FLT_RADIX | radix of exponent representation | |
| 488 | +---------------------+----------------+--------------------------------------------------+ |
Mark Dickinson | b1e58fe | 2011-11-19 16:26:45 +0000 | [diff] [blame] | 489 | | :const:`rounds` | FLT_ROUNDS | integer constant representing the rounding mode | |
| 490 | | | | used for arithmetic operations. This reflects | |
| 491 | | | | the value of the system FLT_ROUNDS macro at | |
| 492 | | | | interpreter startup time. See section 5.2.4.2.2 | |
| 493 | | | | of the C99 standard for an explanation of the | |
| 494 | | | | possible values and their meanings. | |
Mark Dickinson | be5846b | 2010-07-02 20:26:07 +0000 | [diff] [blame] | 495 | +---------------------+----------------+--------------------------------------------------+ |
Christian Heimes | 9385266 | 2007-12-01 12:22:32 +0000 | [diff] [blame] | 496 | |
Mark Dickinson | be5846b | 2010-07-02 20:26:07 +0000 | [diff] [blame] | 497 | The attribute :attr:`sys.float_info.dig` needs further explanation. If |
| 498 | ``s`` is any string representing a decimal number with at most |
| 499 | :attr:`sys.float_info.dig` significant digits, then converting ``s`` to a |
| 500 | float and back again will recover a string representing the same decimal |
| 501 | value:: |
Christian Heimes | 9385266 | 2007-12-01 12:22:32 +0000 | [diff] [blame] | 502 | |
Mark Dickinson | be5846b | 2010-07-02 20:26:07 +0000 | [diff] [blame] | 503 | >>> import sys |
| 504 | >>> sys.float_info.dig |
| 505 | 15 |
| 506 | >>> s = '3.14159265358979' # decimal string with 15 significant digits |
| 507 | >>> format(float(s), '.15g') # convert to float and back -> same value |
| 508 | '3.14159265358979' |
Christian Heimes | 9385266 | 2007-12-01 12:22:32 +0000 | [diff] [blame] | 509 | |
Mark Dickinson | be5846b | 2010-07-02 20:26:07 +0000 | [diff] [blame] | 510 | But for strings with more than :attr:`sys.float_info.dig` significant digits, |
| 511 | this isn't always true:: |
| 512 | |
| 513 | >>> s = '9876543211234567' # 16 significant digits is too many! |
| 514 | >>> format(float(s), '.16g') # conversion changes value |
| 515 | '9876543211234568' |
Christian Heimes | 9385266 | 2007-12-01 12:22:32 +0000 | [diff] [blame] | 516 | |
Mark Dickinson | b08a53a | 2009-04-16 19:52:09 +0000 | [diff] [blame] | 517 | .. data:: float_repr_style |
| 518 | |
| 519 | A string indicating how the :func:`repr` function behaves for |
| 520 | floats. If the string has value ``'short'`` then for a finite |
| 521 | float ``x``, ``repr(x)`` aims to produce a short string with the |
| 522 | property that ``float(repr(x)) == x``. This is the usual behaviour |
| 523 | in Python 3.1 and later. Otherwise, ``float_repr_style`` has value |
| 524 | ``'legacy'`` and ``repr(x)`` behaves in the same way as it did in |
| 525 | versions of Python prior to 3.1. |
| 526 | |
| 527 | .. versionadded:: 3.1 |
| 528 | |
| 529 | |
Antoine Pitrou | f9d0b12 | 2012-12-09 14:28:26 +0100 | [diff] [blame] | 530 | .. function:: getallocatedblocks() |
| 531 | |
| 532 | Return the number of memory blocks currently allocated by the interpreter, |
Antoine Pitrou | 9284053 | 2012-12-17 23:05:59 +0100 | [diff] [blame] | 533 | regardless of their size. This function is mainly useful for tracking |
| 534 | and debugging memory leaks. Because of the interpreter's internal |
| 535 | caches, the result can vary from call to call; you may have to call |
| 536 | :func:`_clear_type_cache()` and :func:`gc.collect()` to get more |
| 537 | predictable results. |
| 538 | |
| 539 | If a Python build or implementation cannot reasonably compute this |
| 540 | information, :func:`getallocatedblocks()` is allowed to return 0 instead. |
Antoine Pitrou | f9d0b12 | 2012-12-09 14:28:26 +0100 | [diff] [blame] | 541 | |
| 542 | .. versionadded:: 3.4 |
| 543 | |
Antoine Pitrou | f9d0b12 | 2012-12-09 14:28:26 +0100 | [diff] [blame] | 544 | |
Victor Stinner | d6958ac | 2016-12-02 01:13:46 +0100 | [diff] [blame] | 545 | .. function:: getandroidapilevel() |
| 546 | |
| 547 | Return the build time API version of Android as an integer. |
| 548 | |
Cheryl Sabella | 2d6097d | 2018-10-12 10:55:20 -0400 | [diff] [blame] | 549 | .. availability:: Android. |
Victor Stinner | d6958ac | 2016-12-02 01:13:46 +0100 | [diff] [blame] | 550 | |
| 551 | .. versionadded:: 3.7 |
| 552 | |
| 553 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 554 | .. function:: getdefaultencoding() |
| 555 | |
| 556 | Return the name of the current default string encoding used by the Unicode |
| 557 | implementation. |
| 558 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 559 | |
| 560 | .. function:: getdlopenflags() |
| 561 | |
Andrew Kuchling | c61b913 | 2013-06-21 10:58:41 -0400 | [diff] [blame] | 562 | Return the current value of the flags that are used for |
| 563 | :c:func:`dlopen` calls. Symbolic names for the flag values can be |
| 564 | found in the :mod:`os` module (``RTLD_xxx`` constants, e.g. |
Cheryl Sabella | 2d6097d | 2018-10-12 10:55:20 -0400 | [diff] [blame] | 565 | :data:`os.RTLD_LAZY`). |
| 566 | |
| 567 | .. availability:: Unix. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 568 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 569 | |
| 570 | .. function:: getfilesystemencoding() |
| 571 | |
Steve Dower | cc16be8 | 2016-09-08 10:35:16 -0700 | [diff] [blame] | 572 | Return the name of the encoding used to convert between Unicode |
| 573 | filenames and bytes filenames. For best compatibility, str should be |
| 574 | used for filenames in all cases, although representing filenames as bytes |
| 575 | is also supported. Functions accepting or returning filenames should support |
| 576 | either str or bytes and internally convert to the system's preferred |
| 577 | representation. |
| 578 | |
| 579 | This encoding is always ASCII-compatible. |
| 580 | |
| 581 | :func:`os.fsencode` and :func:`os.fsdecode` should be used to ensure that |
| 582 | the correct encoding and errors mode are used. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 583 | |
Victor Stinner | 91106cd | 2017-12-13 12:29:09 +0100 | [diff] [blame] | 584 | * In the UTF-8 mode, the encoding is ``utf-8`` on any platform. |
| 585 | |
pxinwr | f4b0a1c | 2019-03-04 17:02:06 +0800 | [diff] [blame] | 586 | * On macOS, the encoding is ``'utf-8'``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 587 | |
Steve Dower | cc16be8 | 2016-09-08 10:35:16 -0700 | [diff] [blame] | 588 | * On Unix, the encoding is the locale encoding. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 589 | |
Steve Dower | cc16be8 | 2016-09-08 10:35:16 -0700 | [diff] [blame] | 590 | * On Windows, the encoding may be ``'utf-8'`` or ``'mbcs'``, depending |
| 591 | on user configuration. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 592 | |
pxinwr | f4b0a1c | 2019-03-04 17:02:06 +0800 | [diff] [blame] | 593 | * On Android, the encoding is ``'utf-8'``. |
| 594 | |
| 595 | * On VxWorks, the encoding is ``'utf-8'``. |
| 596 | |
Victor Stinner | b744ba1 | 2010-05-15 12:27:16 +0000 | [diff] [blame] | 597 | .. versionchanged:: 3.2 |
Victor Stinner | 22d0418 | 2013-12-02 12:16:46 +0100 | [diff] [blame] | 598 | :func:`getfilesystemencoding` result cannot be ``None`` anymore. |
Victor Stinner | b744ba1 | 2010-05-15 12:27:16 +0000 | [diff] [blame] | 599 | |
Steve Dower | cc16be8 | 2016-09-08 10:35:16 -0700 | [diff] [blame] | 600 | .. versionchanged:: 3.6 |
| 601 | Windows is no longer guaranteed to return ``'mbcs'``. See :pep:`529` |
| 602 | and :func:`_enablelegacywindowsfsencoding` for more information. |
| 603 | |
Victor Stinner | 91106cd | 2017-12-13 12:29:09 +0100 | [diff] [blame] | 604 | .. versionchanged:: 3.7 |
| 605 | Return 'utf-8' in the UTF-8 mode. |
| 606 | |
| 607 | |
Steve Dower | cc16be8 | 2016-09-08 10:35:16 -0700 | [diff] [blame] | 608 | .. function:: getfilesystemencodeerrors() |
| 609 | |
| 610 | Return the name of the error mode used to convert between Unicode filenames |
| 611 | and bytes filenames. The encoding name is returned from |
| 612 | :func:`getfilesystemencoding`. |
| 613 | |
| 614 | :func:`os.fsencode` and :func:`os.fsdecode` should be used to ensure that |
| 615 | the correct encoding and errors mode are used. |
| 616 | |
| 617 | .. versionadded:: 3.6 |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 618 | |
| 619 | .. function:: getrefcount(object) |
| 620 | |
| 621 | Return the reference count of the *object*. The count returned is generally one |
| 622 | higher than you might expect, because it includes the (temporary) reference as |
| 623 | an argument to :func:`getrefcount`. |
| 624 | |
| 625 | |
| 626 | .. function:: getrecursionlimit() |
| 627 | |
| 628 | Return the current value of the recursion limit, the maximum depth of the Python |
| 629 | interpreter stack. This limit prevents infinite recursion from causing an |
| 630 | overflow of the C stack and crashing Python. It can be set by |
| 631 | :func:`setrecursionlimit`. |
| 632 | |
| 633 | |
Robert Schuppenies | fbe94c5 | 2008-07-14 10:13:31 +0000 | [diff] [blame] | 634 | .. function:: getsizeof(object[, default]) |
Martin v. Löwis | 00709aa | 2008-06-04 14:18:43 +0000 | [diff] [blame] | 635 | |
| 636 | Return the size of an object in bytes. The object can be any type of |
| 637 | object. All built-in objects will return correct results, but this |
Robert Schuppenies | fbe94c5 | 2008-07-14 10:13:31 +0000 | [diff] [blame] | 638 | does not have to hold true for third-party extensions as it is implementation |
Martin v. Löwis | 00709aa | 2008-06-04 14:18:43 +0000 | [diff] [blame] | 639 | specific. |
| 640 | |
Martin v. Löwis | 1e5d0ff | 2012-06-17 10:40:16 +0200 | [diff] [blame] | 641 | Only the memory consumption directly attributed to the object is |
| 642 | accounted for, not the memory consumption of objects it refers to. |
| 643 | |
Benjamin Peterson | 4ac9ce4 | 2009-10-04 14:49:41 +0000 | [diff] [blame] | 644 | If given, *default* will be returned if the object does not provide means to |
Georg Brandl | ef871f6 | 2010-03-12 10:06:40 +0000 | [diff] [blame] | 645 | retrieve the size. Otherwise a :exc:`TypeError` will be raised. |
Robert Schuppenies | fbe94c5 | 2008-07-14 10:13:31 +0000 | [diff] [blame] | 646 | |
Benjamin Peterson | 4ac9ce4 | 2009-10-04 14:49:41 +0000 | [diff] [blame] | 647 | :func:`getsizeof` calls the object's ``__sizeof__`` method and adds an |
| 648 | additional garbage collector overhead if the object is managed by the garbage |
| 649 | collector. |
Robert Schuppenies | fbe94c5 | 2008-07-14 10:13:31 +0000 | [diff] [blame] | 650 | |
Serhiy Storchaka | 6dff020 | 2016-05-07 10:49:07 +0300 | [diff] [blame] | 651 | See `recursive sizeof recipe <https://code.activestate.com/recipes/577504>`_ |
Raymond Hettinger | c539a2a | 2010-12-17 23:31:30 +0000 | [diff] [blame] | 652 | for an example of using :func:`getsizeof` recursively to find the size of |
| 653 | containers and all their contents. |
Martin v. Löwis | 00709aa | 2008-06-04 14:18:43 +0000 | [diff] [blame] | 654 | |
Antoine Pitrou | d42bc51 | 2009-11-10 23:18:31 +0000 | [diff] [blame] | 655 | .. function:: getswitchinterval() |
| 656 | |
| 657 | Return the interpreter's "thread switch interval"; see |
| 658 | :func:`setswitchinterval`. |
| 659 | |
Antoine Pitrou | 79707ca | 2009-11-11 22:03:32 +0000 | [diff] [blame] | 660 | .. versionadded:: 3.2 |
| 661 | |
Antoine Pitrou | d42bc51 | 2009-11-10 23:18:31 +0000 | [diff] [blame] | 662 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 663 | .. function:: _getframe([depth]) |
| 664 | |
| 665 | Return a frame object from the call stack. If optional integer *depth* is |
| 666 | given, return the frame object that many calls below the top of the stack. If |
| 667 | that is deeper than the call stack, :exc:`ValueError` is raised. The default |
| 668 | for *depth* is zero, returning the frame at the top of the call stack. |
| 669 | |
Steve Dower | b82e17e | 2019-05-23 08:45:22 -0700 | [diff] [blame] | 670 | .. audit-event:: sys._getframe |
| 671 | |
Georg Brandl | 495f7b5 | 2009-10-27 15:28:25 +0000 | [diff] [blame] | 672 | .. impl-detail:: |
| 673 | |
| 674 | This function should be used for internal and specialized purposes only. |
| 675 | It is not guaranteed to exist in all implementations of Python. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 676 | |
| 677 | |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 678 | .. function:: getprofile() |
| 679 | |
| 680 | .. index:: |
| 681 | single: profile function |
| 682 | single: profiler |
| 683 | |
| 684 | Get the profiler function as set by :func:`setprofile`. |
| 685 | |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 686 | |
| 687 | .. function:: gettrace() |
| 688 | |
| 689 | .. index:: |
| 690 | single: trace function |
| 691 | single: debugger |
| 692 | |
| 693 | Get the trace function as set by :func:`settrace`. |
| 694 | |
Georg Brandl | 495f7b5 | 2009-10-27 15:28:25 +0000 | [diff] [blame] | 695 | .. impl-detail:: |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 696 | |
| 697 | The :func:`gettrace` function is intended only for implementing debuggers, |
Georg Brandl | 495f7b5 | 2009-10-27 15:28:25 +0000 | [diff] [blame] | 698 | profilers, coverage tools and the like. Its behavior is part of the |
| 699 | implementation platform, rather than part of the language definition, and |
| 700 | thus may not be available in all Python implementations. |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 701 | |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 702 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 703 | .. function:: getwindowsversion() |
| 704 | |
Eric Smith | 7338a39 | 2010-01-27 00:56:30 +0000 | [diff] [blame] | 705 | Return a named tuple describing the Windows version |
Eric Smith | f7bb578 | 2010-01-27 00:44:57 +0000 | [diff] [blame] | 706 | currently running. The named elements are *major*, *minor*, |
| 707 | *build*, *platform*, *service_pack*, *service_pack_minor*, |
Steve Dower | 74f4af7 | 2016-09-17 17:27:48 -0700 | [diff] [blame] | 708 | *service_pack_major*, *suite_mask*, *product_type* and |
| 709 | *platform_version*. *service_pack* contains a string, |
| 710 | *platform_version* a 3-tuple and all other values are |
Eric Smith | f7bb578 | 2010-01-27 00:44:57 +0000 | [diff] [blame] | 711 | integers. The components can also be accessed by name, so |
| 712 | ``sys.getwindowsversion()[0]`` is equivalent to |
| 713 | ``sys.getwindowsversion().major``. For compatibility with prior |
| 714 | versions, only the first 5 elements are retrievable by indexing. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 715 | |
Steve Dower | 74f4af7 | 2016-09-17 17:27:48 -0700 | [diff] [blame] | 716 | *platform* will be :const:`2 (VER_PLATFORM_WIN32_NT)`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 717 | |
Eric Smith | f7bb578 | 2010-01-27 00:44:57 +0000 | [diff] [blame] | 718 | *product_type* may be one of the following values: |
| 719 | |
| 720 | +---------------------------------------+---------------------------------+ |
| 721 | | Constant | Meaning | |
| 722 | +=======================================+=================================+ |
| 723 | | :const:`1 (VER_NT_WORKSTATION)` | The system is a workstation. | |
| 724 | +---------------------------------------+---------------------------------+ |
| 725 | | :const:`2 (VER_NT_DOMAIN_CONTROLLER)` | The system is a domain | |
| 726 | | | controller. | |
| 727 | +---------------------------------------+---------------------------------+ |
| 728 | | :const:`3 (VER_NT_SERVER)` | The system is a server, but not | |
| 729 | | | a domain controller. | |
| 730 | +---------------------------------------+---------------------------------+ |
| 731 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 732 | This function wraps the Win32 :c:func:`GetVersionEx` function; see the |
| 733 | Microsoft documentation on :c:func:`OSVERSIONINFOEX` for more information |
Eric Smith | f7bb578 | 2010-01-27 00:44:57 +0000 | [diff] [blame] | 734 | about these fields. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 735 | |
Steve Dower | 74f4af7 | 2016-09-17 17:27:48 -0700 | [diff] [blame] | 736 | *platform_version* returns the accurate major version, minor version and |
| 737 | build number of the current operating system, rather than the version that |
| 738 | is being emulated for the process. It is intended for use in logging rather |
| 739 | than for feature detection. |
| 740 | |
Cheryl Sabella | 2d6097d | 2018-10-12 10:55:20 -0400 | [diff] [blame] | 741 | .. availability:: Windows. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 742 | |
Ezio Melotti | 83fc6dd | 2010-01-27 22:44:03 +0000 | [diff] [blame] | 743 | .. versionchanged:: 3.2 |
Eric Smith | f7bb578 | 2010-01-27 00:44:57 +0000 | [diff] [blame] | 744 | Changed to a named tuple and added *service_pack_minor*, |
| 745 | *service_pack_major*, *suite_mask*, and *product_type*. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 746 | |
Steve Dower | 74f4af7 | 2016-09-17 17:27:48 -0700 | [diff] [blame] | 747 | .. versionchanged:: 3.6 |
| 748 | Added *platform_version* |
Mark Dickinson | dc787d2 | 2010-05-23 13:33:13 +0000 | [diff] [blame] | 749 | |
Yury Selivanov | 0366004 | 2016-12-15 17:36:05 -0500 | [diff] [blame] | 750 | |
| 751 | .. function:: get_asyncgen_hooks() |
| 752 | |
| 753 | Returns an *asyncgen_hooks* object, which is similar to a |
| 754 | :class:`~collections.namedtuple` of the form `(firstiter, finalizer)`, |
| 755 | where *firstiter* and *finalizer* are expected to be either ``None`` or |
| 756 | functions which take an :term:`asynchronous generator iterator` as an |
Ville Skyttä | 49b2734 | 2017-08-03 09:00:59 +0300 | [diff] [blame] | 757 | argument, and are used to schedule finalization of an asynchronous |
Yury Selivanov | 0366004 | 2016-12-15 17:36:05 -0500 | [diff] [blame] | 758 | generator by an event loop. |
| 759 | |
| 760 | .. versionadded:: 3.6 |
| 761 | See :pep:`525` for more details. |
| 762 | |
| 763 | .. note:: |
| 764 | This function has been added on a provisional basis (see :pep:`411` |
| 765 | for details.) |
| 766 | |
| 767 | |
Nathaniel J. Smith | fc2f407 | 2018-01-21 06:44:07 -0800 | [diff] [blame] | 768 | .. function:: get_coroutine_origin_tracking_depth() |
| 769 | |
| 770 | Get the current coroutine origin tracking depth, as set by |
Jules Lasne (jlasne) | cb0f5e2 | 2018-12-14 12:28:44 +0100 | [diff] [blame] | 771 | :func:`set_coroutine_origin_tracking_depth`. |
Nathaniel J. Smith | fc2f407 | 2018-01-21 06:44:07 -0800 | [diff] [blame] | 772 | |
| 773 | .. versionadded:: 3.7 |
| 774 | |
| 775 | .. note:: |
| 776 | This function has been added on a provisional basis (see :pep:`411` |
| 777 | for details.) Use it only for debugging purposes. |
| 778 | |
| 779 | |
Mark Dickinson | dc787d2 | 2010-05-23 13:33:13 +0000 | [diff] [blame] | 780 | .. data:: hash_info |
| 781 | |
Benjamin Peterson | 2b8ef2d | 2011-04-20 18:31:22 -0500 | [diff] [blame] | 782 | A :term:`struct sequence` giving parameters of the numeric hash |
| 783 | implementation. For more details about hashing of numeric types, see |
| 784 | :ref:`numeric-hash`. |
Mark Dickinson | dc787d2 | 2010-05-23 13:33:13 +0000 | [diff] [blame] | 785 | |
| 786 | +---------------------+--------------------------------------------------+ |
| 787 | | attribute | explanation | |
| 788 | +=====================+==================================================+ |
| 789 | | :const:`width` | width in bits used for hash values | |
| 790 | +---------------------+--------------------------------------------------+ |
| 791 | | :const:`modulus` | prime modulus P used for numeric hash scheme | |
| 792 | +---------------------+--------------------------------------------------+ |
| 793 | | :const:`inf` | hash value returned for a positive infinity | |
| 794 | +---------------------+--------------------------------------------------+ |
| 795 | | :const:`nan` | hash value returned for a nan | |
| 796 | +---------------------+--------------------------------------------------+ |
| 797 | | :const:`imag` | multiplier used for the imaginary part of a | |
| 798 | | | complex number | |
| 799 | +---------------------+--------------------------------------------------+ |
Christian Heimes | 985ecdc | 2013-11-20 11:46:18 +0100 | [diff] [blame] | 800 | | :const:`algorithm` | name of the algorithm for hashing of str, bytes, | |
| 801 | | | and memoryview | |
| 802 | +---------------------+--------------------------------------------------+ |
| 803 | | :const:`hash_bits` | internal output size of the hash algorithm | |
| 804 | +---------------------+--------------------------------------------------+ |
| 805 | | :const:`seed_bits` | size of the seed key of the hash algorithm | |
| 806 | +---------------------+--------------------------------------------------+ |
| 807 | |
Mark Dickinson | dc787d2 | 2010-05-23 13:33:13 +0000 | [diff] [blame] | 808 | |
| 809 | .. versionadded:: 3.2 |
| 810 | |
R David Murray | f93d3df | 2014-03-17 11:20:29 -0400 | [diff] [blame] | 811 | .. versionchanged:: 3.4 |
Christian Heimes | 985ecdc | 2013-11-20 11:46:18 +0100 | [diff] [blame] | 812 | Added *algorithm*, *hash_bits* and *seed_bits* |
| 813 | |
Mark Dickinson | dc787d2 | 2010-05-23 13:33:13 +0000 | [diff] [blame] | 814 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 815 | .. data:: hexversion |
| 816 | |
| 817 | The version number encoded as a single integer. This is guaranteed to increase |
| 818 | with each version, including proper support for non-production releases. For |
| 819 | example, to test that the Python interpreter is at least version 1.5.2, use:: |
| 820 | |
| 821 | if sys.hexversion >= 0x010502F0: |
| 822 | # use some advanced feature |
| 823 | ... |
| 824 | else: |
| 825 | # use an alternative implementation or warn the user |
| 826 | ... |
| 827 | |
| 828 | This is called ``hexversion`` since it only really looks meaningful when viewed |
| 829 | as the result of passing it to the built-in :func:`hex` function. The |
Éric Araujo | 0abb8b7 | 2011-04-27 16:32:36 +0200 | [diff] [blame] | 830 | :term:`struct sequence` :data:`sys.version_info` may be used for a more |
| 831 | human-friendly encoding of the same information. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 832 | |
Martin Panter | d21e0b5 | 2015-10-10 10:36:22 +0000 | [diff] [blame] | 833 | More details of ``hexversion`` can be found at :ref:`apiabiversion`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 834 | |
Barry Warsaw | 409da15 | 2012-06-03 16:18:47 -0400 | [diff] [blame] | 835 | |
| 836 | .. data:: implementation |
| 837 | |
Barry Warsaw | 9b10e1f | 2012-06-04 11:06:45 -0400 | [diff] [blame] | 838 | An object containing information about the implementation of the |
| 839 | currently running Python interpreter. The following attributes are |
| 840 | required to exist in all Python implementations. |
Barry Warsaw | 409da15 | 2012-06-03 16:18:47 -0400 | [diff] [blame] | 841 | |
Barry Warsaw | 9b10e1f | 2012-06-04 11:06:45 -0400 | [diff] [blame] | 842 | *name* is the implementation's identifier, e.g. ``'cpython'``. The actual |
| 843 | string is defined by the Python implementation, but it is guaranteed to be |
| 844 | lower case. |
Barry Warsaw | 409da15 | 2012-06-03 16:18:47 -0400 | [diff] [blame] | 845 | |
| 846 | *version* is a named tuple, in the same format as |
| 847 | :data:`sys.version_info`. It represents the version of the Python |
| 848 | *implementation*. This has a distinct meaning from the specific |
| 849 | version of the Python *language* to which the currently running |
| 850 | interpreter conforms, which ``sys.version_info`` represents. For |
| 851 | example, for PyPy 1.8 ``sys.implementation.version`` might be |
| 852 | ``sys.version_info(1, 8, 0, 'final', 0)``, whereas ``sys.version_info`` |
Barry Warsaw | 9b10e1f | 2012-06-04 11:06:45 -0400 | [diff] [blame] | 853 | would be ``sys.version_info(2, 7, 2, 'final', 0)``. For CPython they |
Barry Warsaw | 409da15 | 2012-06-03 16:18:47 -0400 | [diff] [blame] | 854 | are the same value, since it is the reference implementation. |
| 855 | |
| 856 | *hexversion* is the implementation version in hexadecimal format, like |
| 857 | :data:`sys.hexversion`. |
| 858 | |
| 859 | *cache_tag* is the tag used by the import machinery in the filenames of |
| 860 | cached modules. By convention, it would be a composite of the |
| 861 | implementation's name and version, like ``'cpython-33'``. However, a |
| 862 | Python implementation may use some other value if appropriate. If |
| 863 | ``cache_tag`` is set to ``None``, it indicates that module caching should |
| 864 | be disabled. |
| 865 | |
Barry Warsaw | 9b10e1f | 2012-06-04 11:06:45 -0400 | [diff] [blame] | 866 | :data:`sys.implementation` may contain additional attributes specific to |
| 867 | the Python implementation. These non-standard attributes must start with |
| 868 | an underscore, and are not described here. Regardless of its contents, |
| 869 | :data:`sys.implementation` will not change during a run of the interpreter, |
| 870 | nor between implementation versions. (It may change between Python |
Georg Brandl | 93a56cd | 2014-10-30 22:25:41 +0100 | [diff] [blame] | 871 | language versions, however.) See :pep:`421` for more information. |
Barry Warsaw | 409da15 | 2012-06-03 16:18:47 -0400 | [diff] [blame] | 872 | |
| 873 | .. versionadded:: 3.3 |
| 874 | |
| 875 | |
Mark Dickinson | bd79264 | 2009-03-18 20:06:12 +0000 | [diff] [blame] | 876 | .. data:: int_info |
| 877 | |
Benjamin Peterson | 2b8ef2d | 2011-04-20 18:31:22 -0500 | [diff] [blame] | 878 | A :term:`struct sequence` that holds information about Python's internal |
| 879 | representation of integers. The attributes are read only. |
Mark Dickinson | bd79264 | 2009-03-18 20:06:12 +0000 | [diff] [blame] | 880 | |
Georg Brandl | 44ea77b | 2013-03-28 13:28:44 +0100 | [diff] [blame] | 881 | .. tabularcolumns:: |l|L| |
| 882 | |
Mark Dickinson | bd79264 | 2009-03-18 20:06:12 +0000 | [diff] [blame] | 883 | +-------------------------+----------------------------------------------+ |
R David Murray | 9beb34e | 2011-04-30 16:35:29 -0400 | [diff] [blame] | 884 | | Attribute | Explanation | |
Mark Dickinson | bd79264 | 2009-03-18 20:06:12 +0000 | [diff] [blame] | 885 | +=========================+==============================================+ |
| 886 | | :const:`bits_per_digit` | number of bits held in each digit. Python | |
| 887 | | | integers are stored internally in base | |
| 888 | | | ``2**int_info.bits_per_digit`` | |
| 889 | +-------------------------+----------------------------------------------+ |
| 890 | | :const:`sizeof_digit` | size in bytes of the C type used to | |
| 891 | | | represent a digit | |
| 892 | +-------------------------+----------------------------------------------+ |
| 893 | |
Mark Dickinson | d72c7b6 | 2009-03-20 16:00:49 +0000 | [diff] [blame] | 894 | .. versionadded:: 3.1 |
| 895 | |
Mark Dickinson | bd79264 | 2009-03-18 20:06:12 +0000 | [diff] [blame] | 896 | |
Antoine Pitrou | 1a6cb30 | 2013-05-04 20:08:35 +0200 | [diff] [blame] | 897 | .. data:: __interactivehook__ |
| 898 | |
Larry Hastings | 3732ed2 | 2014-03-15 21:13:56 -0700 | [diff] [blame] | 899 | When this attribute exists, its value is automatically called (with no |
| 900 | arguments) when the interpreter is launched in :ref:`interactive mode |
| 901 | <tut-interactive>`. This is done after the :envvar:`PYTHONSTARTUP` file is |
| 902 | read, so that you can set this hook there. The :mod:`site` module |
| 903 | :ref:`sets this <rlcompleter-config>`. |
Antoine Pitrou | 1a6cb30 | 2013-05-04 20:08:35 +0200 | [diff] [blame] | 904 | |
| 905 | .. versionadded:: 3.4 |
| 906 | |
| 907 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 908 | .. function:: intern(string) |
| 909 | |
| 910 | Enter *string* in the table of "interned" strings and return the interned string |
| 911 | -- which is *string* itself or a copy. Interning strings is useful to gain a |
| 912 | little performance on dictionary lookup -- if the keys in a dictionary are |
| 913 | interned, and the lookup key is interned, the key comparisons (after hashing) |
| 914 | can be done by a pointer compare instead of a string compare. Normally, the |
| 915 | names used in Python programs are automatically interned, and the dictionaries |
| 916 | used to hold module, class or instance attributes have interned keys. |
| 917 | |
Georg Brandl | 55ac8f0 | 2007-09-01 13:51:09 +0000 | [diff] [blame] | 918 | Interned strings are not immortal; you must keep a reference to the return |
| 919 | value of :func:`intern` around to benefit from it. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 920 | |
| 921 | |
Antoine Pitrou | 5db1bb8 | 2014-12-07 01:28:27 +0100 | [diff] [blame] | 922 | .. function:: is_finalizing() |
| 923 | |
| 924 | Return :const:`True` if the Python interpreter is |
| 925 | :term:`shutting down <interpreter shutdown>`, :const:`False` otherwise. |
| 926 | |
| 927 | .. versionadded:: 3.5 |
| 928 | |
| 929 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 930 | .. data:: last_type |
| 931 | last_value |
| 932 | last_traceback |
| 933 | |
| 934 | These three variables are not always defined; they are set when an exception is |
| 935 | not handled and the interpreter prints an error message and a stack traceback. |
| 936 | Their intended use is to allow an interactive user to import a debugger module |
| 937 | and engage in post-mortem debugging without having to re-execute the command |
| 938 | that caused the error. (Typical use is ``import pdb; pdb.pm()`` to enter the |
Alexander Belopolsky | f0a0d14 | 2010-10-27 03:06:43 +0000 | [diff] [blame] | 939 | post-mortem debugger; see :mod:`pdb` module for |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 940 | more information.) |
| 941 | |
| 942 | The meaning of the variables is the same as that of the return values from |
Georg Brandl | 482b151 | 2010-03-21 09:02:59 +0000 | [diff] [blame] | 943 | :func:`exc_info` above. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 944 | |
| 945 | |
Christian Heimes | a37d4c6 | 2007-12-04 23:02:19 +0000 | [diff] [blame] | 946 | .. data:: maxsize |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 947 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 948 | An integer giving the maximum value a variable of type :c:type:`Py_ssize_t` can |
Georg Brandl | 3377055 | 2007-12-15 09:55:35 +0000 | [diff] [blame] | 949 | take. It's usually ``2**31 - 1`` on a 32-bit platform and ``2**63 - 1`` on a |
| 950 | 64-bit platform. |
Christian Heimes | a37d4c6 | 2007-12-04 23:02:19 +0000 | [diff] [blame] | 951 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 952 | |
| 953 | .. data:: maxunicode |
| 954 | |
Ezio Melotti | 48a2f8f | 2011-09-29 00:18:19 +0300 | [diff] [blame] | 955 | An integer giving the value of the largest Unicode code point, |
| 956 | i.e. ``1114111`` (``0x10FFFF`` in hexadecimal). |
| 957 | |
| 958 | .. versionchanged:: 3.3 |
Éric Araujo | 525b1e9 | 2011-10-05 01:06:31 +0200 | [diff] [blame] | 959 | Before :pep:`393`, ``sys.maxunicode`` used to be either ``0xFFFF`` |
Ezio Melotti | 48a2f8f | 2011-09-29 00:18:19 +0300 | [diff] [blame] | 960 | or ``0x10FFFF``, depending on the configuration option that specified |
| 961 | whether Unicode characters were stored as UCS-2 or UCS-4. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 962 | |
| 963 | |
Brett Cannon | e43b060 | 2009-03-21 03:11:16 +0000 | [diff] [blame] | 964 | .. data:: meta_path |
| 965 | |
Brett Cannon | ccddbb1 | 2015-12-04 15:46:21 -0800 | [diff] [blame] | 966 | A list of :term:`meta path finder` objects that have their |
| 967 | :meth:`~importlib.abc.MetaPathFinder.find_spec` methods called to see if one |
| 968 | of the objects can find the module to be imported. The |
| 969 | :meth:`~importlib.abc.MetaPathFinder.find_spec` method is called with at |
| 970 | least the absolute name of the module being imported. If the module to be |
| 971 | imported is contained in a package, then the parent package's :attr:`__path__` |
| 972 | attribute is passed in as a second argument. The method returns a |
| 973 | :term:`module spec`, or ``None`` if the module cannot be found. |
Brett Cannon | e43b060 | 2009-03-21 03:11:16 +0000 | [diff] [blame] | 974 | |
Brett Cannon | ccddbb1 | 2015-12-04 15:46:21 -0800 | [diff] [blame] | 975 | .. seealso:: |
Brett Cannon | e43b060 | 2009-03-21 03:11:16 +0000 | [diff] [blame] | 976 | |
Brett Cannon | ccddbb1 | 2015-12-04 15:46:21 -0800 | [diff] [blame] | 977 | :class:`importlib.abc.MetaPathFinder` |
| 978 | The abstract base class defining the interface of finder objects on |
| 979 | :data:`meta_path`. |
| 980 | :class:`importlib.machinery.ModuleSpec` |
| 981 | The concrete class which |
| 982 | :meth:`~importlib.abc.MetaPathFinder.find_spec` should return |
| 983 | instances of. |
Brett Cannon | e43b060 | 2009-03-21 03:11:16 +0000 | [diff] [blame] | 984 | |
Brett Cannon | ccddbb1 | 2015-12-04 15:46:21 -0800 | [diff] [blame] | 985 | .. versionchanged:: 3.4 |
| 986 | |
| 987 | :term:`Module specs <module spec>` were introduced in Python 3.4, by |
| 988 | :pep:`451`. Earlier versions of Python looked for a method called |
| 989 | :meth:`~importlib.abc.MetaPathFinder.find_module`. |
| 990 | This is still called as a fallback if a :data:`meta_path` entry doesn't |
| 991 | have a :meth:`~importlib.abc.MetaPathFinder.find_spec` method. |
Brett Cannon | e43b060 | 2009-03-21 03:11:16 +0000 | [diff] [blame] | 992 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 993 | .. data:: modules |
| 994 | |
| 995 | This is a dictionary that maps module names to modules which have already been |
| 996 | loaded. This can be manipulated to force reloading of modules and other tricks. |
Brett Cannon | c3511c1 | 2013-05-24 08:05:07 -0400 | [diff] [blame] | 997 | However, replacing the dictionary will not necessarily work as expected and |
| 998 | deleting essential items from the dictionary may cause Python to fail. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 999 | |
| 1000 | |
| 1001 | .. data:: path |
| 1002 | |
| 1003 | .. index:: triple: module; search; path |
| 1004 | |
| 1005 | A list of strings that specifies the search path for modules. Initialized from |
| 1006 | the environment variable :envvar:`PYTHONPATH`, plus an installation-dependent |
| 1007 | default. |
| 1008 | |
| 1009 | As initialized upon program startup, the first item of this list, ``path[0]``, |
| 1010 | is the directory containing the script that was used to invoke the Python |
| 1011 | interpreter. If the script directory is not available (e.g. if the interpreter |
| 1012 | is invoked interactively or if the script is read from standard input), |
| 1013 | ``path[0]`` is the empty string, which directs Python to search modules in the |
| 1014 | current directory first. Notice that the script directory is inserted *before* |
| 1015 | the entries inserted as a result of :envvar:`PYTHONPATH`. |
| 1016 | |
Barry Warsaw | 82c1c78 | 2012-11-20 15:22:51 -0500 | [diff] [blame] | 1017 | A program is free to modify this list for its own purposes. Only strings |
| 1018 | and bytes should be added to :data:`sys.path`; all other data types are |
| 1019 | ignored during import. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1020 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1021 | |
Benjamin Peterson | 058e31e | 2009-01-16 03:54:08 +0000 | [diff] [blame] | 1022 | .. seealso:: |
| 1023 | Module :mod:`site` This describes how to use .pth files to extend |
| 1024 | :data:`sys.path`. |
| 1025 | |
| 1026 | |
Brett Cannon | e43b060 | 2009-03-21 03:11:16 +0000 | [diff] [blame] | 1027 | .. data:: path_hooks |
| 1028 | |
| 1029 | A list of callables that take a path argument to try to create a |
| 1030 | :term:`finder` for the path. If a finder can be created, it is to be |
| 1031 | returned by the callable, else raise :exc:`ImportError`. |
| 1032 | |
| 1033 | Originally specified in :pep:`302`. |
| 1034 | |
| 1035 | |
| 1036 | .. data:: path_importer_cache |
| 1037 | |
| 1038 | A dictionary acting as a cache for :term:`finder` objects. The keys are |
| 1039 | paths that have been passed to :data:`sys.path_hooks` and the values are |
| 1040 | the finders that are found. If a path is a valid file system path but no |
Brett Cannon | 2514b48 | 2013-03-13 10:46:22 -0700 | [diff] [blame] | 1041 | finder is found on :data:`sys.path_hooks` then ``None`` is |
| 1042 | stored. |
Brett Cannon | e43b060 | 2009-03-21 03:11:16 +0000 | [diff] [blame] | 1043 | |
| 1044 | Originally specified in :pep:`302`. |
| 1045 | |
Brett Cannon | 2514b48 | 2013-03-13 10:46:22 -0700 | [diff] [blame] | 1046 | .. versionchanged:: 3.3 |
| 1047 | ``None`` is stored instead of :class:`imp.NullImporter` when no finder |
| 1048 | is found. |
| 1049 | |
Brett Cannon | e43b060 | 2009-03-21 03:11:16 +0000 | [diff] [blame] | 1050 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1051 | .. data:: platform |
| 1052 | |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 1053 | This string contains a platform identifier that can be used to append |
| 1054 | platform-specific components to :data:`sys.path`, for instance. |
| 1055 | |
Michael Felt | 9d949f7 | 2019-04-12 16:15:32 +0200 | [diff] [blame] | 1056 | For Unix systems, except on Linux and AIX, this is the lowercased OS name as |
Victor Stinner | 795eaeb | 2011-08-21 12:08:11 +0200 | [diff] [blame] | 1057 | returned by ``uname -s`` with the first part of the version as returned by |
| 1058 | ``uname -r`` appended, e.g. ``'sunos5'`` or ``'freebsd8'``, *at the time |
| 1059 | when Python was built*. Unless you want to test for a specific system |
| 1060 | version, it is therefore recommended to use the following idiom:: |
Antoine Pitrou | a83cdaa | 2011-07-09 15:54:23 +0200 | [diff] [blame] | 1061 | |
Victor Stinner | 795eaeb | 2011-08-21 12:08:11 +0200 | [diff] [blame] | 1062 | if sys.platform.startswith('freebsd'): |
| 1063 | # FreeBSD-specific code here... |
Georg Brandl | a47e53e | 2011-09-03 09:26:09 +0200 | [diff] [blame] | 1064 | elif sys.platform.startswith('linux'): |
Antoine Pitrou | a83cdaa | 2011-07-09 15:54:23 +0200 | [diff] [blame] | 1065 | # Linux-specific code here... |
Michael Felt | 9d949f7 | 2019-04-12 16:15:32 +0200 | [diff] [blame] | 1066 | elif sys.platform.startswith('aix'): |
| 1067 | # AIX-specific code here... |
Antoine Pitrou | a83cdaa | 2011-07-09 15:54:23 +0200 | [diff] [blame] | 1068 | |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 1069 | For other systems, the values are: |
| 1070 | |
| 1071 | ================ =========================== |
Éric Araujo | 3f7c0e4 | 2012-12-08 22:53:43 -0500 | [diff] [blame] | 1072 | System ``platform`` value |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 1073 | ================ =========================== |
Michael Felt | 9d949f7 | 2019-04-12 16:15:32 +0200 | [diff] [blame] | 1074 | AIX ``'aix'`` |
Victor Stinner | 795eaeb | 2011-08-21 12:08:11 +0200 | [diff] [blame] | 1075 | Linux ``'linux'`` |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 1076 | Windows ``'win32'`` |
| 1077 | Windows/Cygwin ``'cygwin'`` |
pxinwr | f4b0a1c | 2019-03-04 17:02:06 +0800 | [diff] [blame] | 1078 | macOS ``'darwin'`` |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 1079 | ================ =========================== |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1080 | |
Victor Stinner | 795eaeb | 2011-08-21 12:08:11 +0200 | [diff] [blame] | 1081 | .. versionchanged:: 3.3 |
| 1082 | On Linux, :attr:`sys.platform` doesn't contain the major version anymore. |
Georg Brandl | fbd1e04 | 2011-09-04 08:42:26 +0200 | [diff] [blame] | 1083 | It is always ``'linux'``, instead of ``'linux2'`` or ``'linux3'``. Since |
| 1084 | older Python versions include the version number, it is recommended to |
| 1085 | always use the ``startswith`` idiom presented above. |
Victor Stinner | 795eaeb | 2011-08-21 12:08:11 +0200 | [diff] [blame] | 1086 | |
Michael Felt | 9d949f7 | 2019-04-12 16:15:32 +0200 | [diff] [blame] | 1087 | .. versionchanged:: 3.8 |
| 1088 | On AIX, :attr:`sys.platform` doesn't contain the major version anymore. |
| 1089 | It is always ``'aix'``, instead of ``'aix5'`` or ``'aix7'``. Since |
| 1090 | older Python versions include the version number, it is recommended to |
| 1091 | always use the ``startswith`` idiom presented above. |
| 1092 | |
Antoine Pitrou | a83cdaa | 2011-07-09 15:54:23 +0200 | [diff] [blame] | 1093 | .. seealso:: |
Georg Brandl | eb25fb7 | 2012-02-23 21:12:39 +0100 | [diff] [blame] | 1094 | |
Antoine Pitrou | a83cdaa | 2011-07-09 15:54:23 +0200 | [diff] [blame] | 1095 | :attr:`os.name` has a coarser granularity. :func:`os.uname` gives |
| 1096 | system-dependent version information. |
| 1097 | |
| 1098 | The :mod:`platform` module provides detailed checks for the |
| 1099 | system's identity. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1100 | |
Georg Brandl | fbd1e04 | 2011-09-04 08:42:26 +0200 | [diff] [blame] | 1101 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1102 | .. data:: prefix |
| 1103 | |
| 1104 | A string giving the site-specific directory prefix where the platform |
| 1105 | independent Python files are installed; by default, this is the string |
Éric Araujo | 713d303 | 2010-11-18 16:38:46 +0000 | [diff] [blame] | 1106 | ``'/usr/local'``. This can be set at build time with the ``--prefix`` |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1107 | argument to the :program:`configure` script. The main collection of Python |
Georg Brandl | a673eb8 | 2012-03-04 16:17:05 +0100 | [diff] [blame] | 1108 | library modules is installed in the directory :file:`{prefix}/lib/python{X.Y}` |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1109 | while the platform independent header files (all except :file:`pyconfig.h`) are |
Georg Brandl | eb25fb7 | 2012-02-23 21:12:39 +0100 | [diff] [blame] | 1110 | stored in :file:`{prefix}/include/python{X.Y}`, where *X.Y* is the version |
Éric Araujo | 58a9153 | 2011-10-05 01:28:24 +0200 | [diff] [blame] | 1111 | number of Python, for example ``3.2``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1112 | |
Vinay Sajip | cd9b746 | 2012-07-09 10:37:01 +0100 | [diff] [blame] | 1113 | .. note:: If a :ref:`virtual environment <venv-def>` is in effect, this |
| 1114 | value will be changed in ``site.py`` to point to the virtual |
| 1115 | environment. The value for the Python installation will still be |
| 1116 | available, via :data:`base_prefix`. |
Vinay Sajip | 7ded1f0 | 2012-05-26 03:45:29 +0100 | [diff] [blame] | 1117 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1118 | |
| 1119 | .. data:: ps1 |
| 1120 | ps2 |
| 1121 | |
| 1122 | .. index:: |
| 1123 | single: interpreter prompts |
| 1124 | single: prompts, interpreter |
Serhiy Storchaka | ddb961d | 2018-10-26 09:00:49 +0300 | [diff] [blame] | 1125 | single: >>>; interpreter prompt |
| 1126 | single: ...; interpreter prompt |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1127 | |
| 1128 | Strings specifying the primary and secondary prompt of the interpreter. These |
| 1129 | are only defined if the interpreter is in interactive mode. Their initial |
| 1130 | values in this case are ``'>>> '`` and ``'... '``. If a non-string object is |
| 1131 | assigned to either variable, its :func:`str` is re-evaluated each time the |
| 1132 | interpreter prepares to read a new interactive command; this can be used to |
| 1133 | implement a dynamic prompt. |
| 1134 | |
| 1135 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1136 | .. function:: setdlopenflags(n) |
| 1137 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1138 | Set the flags used by the interpreter for :c:func:`dlopen` calls, such as when |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1139 | the interpreter loads extension modules. Among other things, this will enable a |
| 1140 | lazy resolving of symbols when importing a module, if called as |
| 1141 | ``sys.setdlopenflags(0)``. To share symbols across extension modules, call as |
Andrew Kuchling | c61b913 | 2013-06-21 10:58:41 -0400 | [diff] [blame] | 1142 | ``sys.setdlopenflags(os.RTLD_GLOBAL)``. Symbolic names for the flag values |
Victor Stinner | 8b905bd | 2011-10-25 13:34:04 +0200 | [diff] [blame] | 1143 | can be found in the :mod:`os` module (``RTLD_xxx`` constants, e.g. |
| 1144 | :data:`os.RTLD_LAZY`). |
| 1145 | |
Cheryl Sabella | 2d6097d | 2018-10-12 10:55:20 -0400 | [diff] [blame] | 1146 | .. availability:: Unix. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1147 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1148 | .. function:: setprofile(profilefunc) |
| 1149 | |
| 1150 | .. index:: |
| 1151 | single: profile function |
| 1152 | single: profiler |
| 1153 | |
| 1154 | Set the system's profile function, which allows you to implement a Python source |
| 1155 | code profiler in Python. See chapter :ref:`profile` for more information on the |
| 1156 | Python profiler. The system's profile function is called similarly to the |
Pablo Galindo | 131fd7f | 2018-01-24 12:57:49 +0000 | [diff] [blame] | 1157 | system's trace function (see :func:`settrace`), but it is called with different events, |
| 1158 | for example it isn't called for each executed line of code (only on call and return, |
| 1159 | but the return event is reported even when an exception has been set). The function is |
| 1160 | thread-specific, but there is no way for the profiler to know about context switches between |
| 1161 | threads, so it does not make sense to use this in the presence of multiple threads. Also, |
Xiang Zhang | 60da99b | 2018-01-27 23:04:47 +0800 | [diff] [blame] | 1162 | its return value is not used, so it can simply return ``None``. Error in the profile |
| 1163 | function will cause itself unset. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1164 | |
Pablo Galindo | 131fd7f | 2018-01-24 12:57:49 +0000 | [diff] [blame] | 1165 | Profile functions should have three arguments: *frame*, *event*, and |
| 1166 | *arg*. *frame* is the current stack frame. *event* is a string: ``'call'``, |
| 1167 | ``'return'``, ``'c_call'``, ``'c_return'``, or ``'c_exception'``. *arg* depends |
| 1168 | on the event type. |
| 1169 | |
Steve Dower | b82e17e | 2019-05-23 08:45:22 -0700 | [diff] [blame] | 1170 | .. audit-event:: sys.setprofile |
| 1171 | |
Pablo Galindo | 131fd7f | 2018-01-24 12:57:49 +0000 | [diff] [blame] | 1172 | The events have the following meaning: |
| 1173 | |
| 1174 | ``'call'`` |
| 1175 | A function is called (or some other code block entered). The |
| 1176 | profile function is called; *arg* is ``None``. |
| 1177 | |
| 1178 | ``'return'`` |
| 1179 | A function (or other code block) is about to return. The profile |
| 1180 | function is called; *arg* is the value that will be returned, or ``None`` |
| 1181 | if the event is caused by an exception being raised. |
| 1182 | |
| 1183 | ``'c_call'`` |
| 1184 | A C function is about to be called. This may be an extension function or |
| 1185 | a built-in. *arg* is the C function object. |
| 1186 | |
| 1187 | ``'c_return'`` |
| 1188 | A C function has returned. *arg* is the C function object. |
| 1189 | |
| 1190 | ``'c_exception'`` |
| 1191 | A C function has raised an exception. *arg* is the C function object. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1192 | |
| 1193 | .. function:: setrecursionlimit(limit) |
| 1194 | |
| 1195 | Set the maximum depth of the Python interpreter stack to *limit*. This limit |
| 1196 | prevents infinite recursion from causing an overflow of the C stack and crashing |
| 1197 | Python. |
| 1198 | |
| 1199 | The highest possible limit is platform-dependent. A user may need to set the |
Georg Brandl | 5166375 | 2011-05-13 06:55:28 +0200 | [diff] [blame] | 1200 | limit higher when they have a program that requires deep recursion and a platform |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1201 | that supports a higher limit. This should be done with care, because a too-high |
| 1202 | limit can lead to a crash. |
| 1203 | |
Victor Stinner | 50856d5 | 2015-10-13 00:11:21 +0200 | [diff] [blame] | 1204 | If the new limit is too low at the current recursion depth, a |
| 1205 | :exc:`RecursionError` exception is raised. |
| 1206 | |
| 1207 | .. versionchanged:: 3.5.1 |
| 1208 | A :exc:`RecursionError` exception is now raised if the new limit is too |
| 1209 | low at the current recursion depth. |
| 1210 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1211 | |
Antoine Pitrou | d42bc51 | 2009-11-10 23:18:31 +0000 | [diff] [blame] | 1212 | .. function:: setswitchinterval(interval) |
| 1213 | |
| 1214 | Set the interpreter's thread switch interval (in seconds). This floating-point |
| 1215 | value determines the ideal duration of the "timeslices" allocated to |
| 1216 | concurrently running Python threads. Please note that the actual value |
| 1217 | can be higher, especially if long-running internal functions or methods |
| 1218 | are used. Also, which thread becomes scheduled at the end of the interval |
| 1219 | is the operating system's decision. The interpreter doesn't have its |
| 1220 | own scheduler. |
| 1221 | |
Antoine Pitrou | 79707ca | 2009-11-11 22:03:32 +0000 | [diff] [blame] | 1222 | .. versionadded:: 3.2 |
| 1223 | |
Antoine Pitrou | d42bc51 | 2009-11-10 23:18:31 +0000 | [diff] [blame] | 1224 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1225 | .. function:: settrace(tracefunc) |
| 1226 | |
| 1227 | .. index:: |
| 1228 | single: trace function |
| 1229 | single: debugger |
| 1230 | |
| 1231 | Set the system's trace function, which allows you to implement a Python |
Amaury Forgeot d'Arc | b0c2916 | 2008-11-22 22:18:04 +0000 | [diff] [blame] | 1232 | source code debugger in Python. The function is thread-specific; for a |
Stefan Hoelzl | 245f528 | 2019-05-17 10:50:03 +0200 | [diff] [blame] | 1233 | debugger to support multiple threads, it must register a trace function using |
| 1234 | :func:`settrace` for each thread being debugged or use :func:`threading.settrace`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1235 | |
Amaury Forgeot d'Arc | b0c2916 | 2008-11-22 22:18:04 +0000 | [diff] [blame] | 1236 | Trace functions should have three arguments: *frame*, *event*, and |
| 1237 | *arg*. *frame* is the current stack frame. *event* is a string: ``'call'``, |
Pablo Galindo | 131fd7f | 2018-01-24 12:57:49 +0000 | [diff] [blame] | 1238 | ``'line'``, ``'return'``, ``'exception'`` or ``'opcode'``. *arg* depends on |
| 1239 | the event type. |
Amaury Forgeot d'Arc | b0c2916 | 2008-11-22 22:18:04 +0000 | [diff] [blame] | 1240 | |
| 1241 | The trace function is invoked (with *event* set to ``'call'``) whenever a new |
| 1242 | local scope is entered; it should return a reference to a local trace |
| 1243 | function to be used that scope, or ``None`` if the scope shouldn't be traced. |
| 1244 | |
| 1245 | The local trace function should return a reference to itself (or to another |
| 1246 | function for further tracing in that scope), or ``None`` to turn off tracing |
| 1247 | in that scope. |
| 1248 | |
Xiang Zhang | 60da99b | 2018-01-27 23:04:47 +0800 | [diff] [blame] | 1249 | If there is any error occurred in the trace function, it will be unset, just |
| 1250 | like ``settrace(None)`` is called. |
| 1251 | |
Amaury Forgeot d'Arc | b0c2916 | 2008-11-22 22:18:04 +0000 | [diff] [blame] | 1252 | The events have the following meaning: |
| 1253 | |
Georg Brandl | 48310cd | 2009-01-03 21:18:54 +0000 | [diff] [blame] | 1254 | ``'call'`` |
Amaury Forgeot d'Arc | b0c2916 | 2008-11-22 22:18:04 +0000 | [diff] [blame] | 1255 | A function is called (or some other code block entered). The |
| 1256 | global trace function is called; *arg* is ``None``; the return value |
| 1257 | specifies the local trace function. |
| 1258 | |
| 1259 | ``'line'`` |
Alexandre Vassalotti | 7b82b40 | 2009-07-21 04:30:03 +0000 | [diff] [blame] | 1260 | The interpreter is about to execute a new line of code or re-execute the |
| 1261 | condition of a loop. The local trace function is called; *arg* is |
| 1262 | ``None``; the return value specifies the new local trace function. See |
| 1263 | :file:`Objects/lnotab_notes.txt` for a detailed explanation of how this |
| 1264 | works. |
Nick Coghlan | 5a85167 | 2017-09-08 10:14:16 +1000 | [diff] [blame] | 1265 | Per-line events may be disabled for a frame by setting |
| 1266 | :attr:`f_trace_lines` to :const:`False` on that frame. |
Amaury Forgeot d'Arc | b0c2916 | 2008-11-22 22:18:04 +0000 | [diff] [blame] | 1267 | |
| 1268 | ``'return'`` |
| 1269 | A function (or other code block) is about to return. The local trace |
Georg Brandl | d0b0e1d | 2010-10-15 16:42:37 +0000 | [diff] [blame] | 1270 | function is called; *arg* is the value that will be returned, or ``None`` |
| 1271 | if the event is caused by an exception being raised. The trace function's |
| 1272 | return value is ignored. |
Amaury Forgeot d'Arc | b0c2916 | 2008-11-22 22:18:04 +0000 | [diff] [blame] | 1273 | |
| 1274 | ``'exception'`` |
| 1275 | An exception has occurred. The local trace function is called; *arg* is a |
| 1276 | tuple ``(exception, value, traceback)``; the return value specifies the |
| 1277 | new local trace function. |
| 1278 | |
Nick Coghlan | 5a85167 | 2017-09-08 10:14:16 +1000 | [diff] [blame] | 1279 | ``'opcode'`` |
| 1280 | The interpreter is about to execute a new opcode (see :mod:`dis` for |
| 1281 | opcode details). The local trace function is called; *arg* is |
| 1282 | ``None``; the return value specifies the new local trace function. |
| 1283 | Per-opcode events are not emitted by default: they must be explicitly |
| 1284 | requested by setting :attr:`f_trace_opcodes` to :const:`True` on the |
| 1285 | frame. |
| 1286 | |
Amaury Forgeot d'Arc | b0c2916 | 2008-11-22 22:18:04 +0000 | [diff] [blame] | 1287 | Note that as an exception is propagated down the chain of callers, an |
| 1288 | ``'exception'`` event is generated at each level. |
| 1289 | |
| 1290 | For more information on code and frame objects, refer to :ref:`types`. |
| 1291 | |
Steve Dower | b82e17e | 2019-05-23 08:45:22 -0700 | [diff] [blame] | 1292 | .. audit-event:: sys.settrace |
| 1293 | |
Georg Brandl | 495f7b5 | 2009-10-27 15:28:25 +0000 | [diff] [blame] | 1294 | .. impl-detail:: |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1295 | |
| 1296 | The :func:`settrace` function is intended only for implementing debuggers, |
Georg Brandl | 495f7b5 | 2009-10-27 15:28:25 +0000 | [diff] [blame] | 1297 | profilers, coverage tools and the like. Its behavior is part of the |
| 1298 | implementation platform, rather than part of the language definition, and |
| 1299 | thus may not be available in all Python implementations. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1300 | |
Nick Coghlan | 5a85167 | 2017-09-08 10:14:16 +1000 | [diff] [blame] | 1301 | .. versionchanged:: 3.7 |
| 1302 | |
| 1303 | ``'opcode'`` event type added; :attr:`f_trace_lines` and |
| 1304 | :attr:`f_trace_opcodes` attributes added to frames |
| 1305 | |
Yury Selivanov | 0366004 | 2016-12-15 17:36:05 -0500 | [diff] [blame] | 1306 | .. function:: set_asyncgen_hooks(firstiter, finalizer) |
| 1307 | |
| 1308 | Accepts two optional keyword arguments which are callables that accept an |
| 1309 | :term:`asynchronous generator iterator` as an argument. The *firstiter* |
| 1310 | callable will be called when an asynchronous generator is iterated for the |
| 1311 | first time. The *finalizer* will be called when an asynchronous generator |
| 1312 | is about to be garbage collected. |
| 1313 | |
Steve Dower | b82e17e | 2019-05-23 08:45:22 -0700 | [diff] [blame] | 1314 | .. audit-event:: sys.set_asyncgen_hooks_firstiter |
| 1315 | |
| 1316 | .. audit-event:: sys.set_asyncgen_hooks_finalizer |
| 1317 | |
| 1318 | Two auditing events are raised because the underlying API consists of two |
| 1319 | calls, each of which must raise its own event. |
| 1320 | |
Yury Selivanov | 0366004 | 2016-12-15 17:36:05 -0500 | [diff] [blame] | 1321 | .. versionadded:: 3.6 |
| 1322 | See :pep:`525` for more details, and for a reference example of a |
| 1323 | *finalizer* method see the implementation of |
| 1324 | ``asyncio.Loop.shutdown_asyncgens`` in |
| 1325 | :source:`Lib/asyncio/base_events.py` |
| 1326 | |
| 1327 | .. note:: |
| 1328 | This function has been added on a provisional basis (see :pep:`411` |
| 1329 | for details.) |
| 1330 | |
Nathaniel J. Smith | fc2f407 | 2018-01-21 06:44:07 -0800 | [diff] [blame] | 1331 | .. function:: set_coroutine_origin_tracking_depth(depth) |
| 1332 | |
| 1333 | Allows enabling or disabling coroutine origin tracking. When |
| 1334 | enabled, the ``cr_origin`` attribute on coroutine objects will |
| 1335 | contain a tuple of (filename, line number, function name) tuples |
| 1336 | describing the traceback where the coroutine object was created, |
| 1337 | with the most recent call first. When disabled, ``cr_origin`` will |
| 1338 | be None. |
| 1339 | |
| 1340 | To enable, pass a *depth* value greater than zero; this sets the |
| 1341 | number of frames whose information will be captured. To disable, |
| 1342 | pass set *depth* to zero. |
| 1343 | |
| 1344 | This setting is thread-specific. |
| 1345 | |
| 1346 | .. versionadded:: 3.7 |
| 1347 | |
| 1348 | .. note:: |
| 1349 | This function has been added on a provisional basis (see :pep:`411` |
| 1350 | for details.) Use it only for debugging purposes. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1351 | |
Steve Dower | cc16be8 | 2016-09-08 10:35:16 -0700 | [diff] [blame] | 1352 | .. function:: _enablelegacywindowsfsencoding() |
| 1353 | |
| 1354 | Changes the default filesystem encoding and errors mode to 'mbcs' and |
| 1355 | 'replace' respectively, for consistency with versions of Python prior to 3.6. |
| 1356 | |
| 1357 | This is equivalent to defining the :envvar:`PYTHONLEGACYWINDOWSFSENCODING` |
| 1358 | environment variable before launching Python. |
| 1359 | |
Cheryl Sabella | 2d6097d | 2018-10-12 10:55:20 -0400 | [diff] [blame] | 1360 | .. availability:: Windows. |
Steve Dower | cc16be8 | 2016-09-08 10:35:16 -0700 | [diff] [blame] | 1361 | |
| 1362 | .. versionadded:: 3.6 |
| 1363 | See :pep:`529` for more details. |
Yury Selivanov | d4cbbeb | 2015-05-31 17:13:08 -0400 | [diff] [blame] | 1364 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1365 | .. data:: stdin |
| 1366 | stdout |
| 1367 | stderr |
| 1368 | |
Antoine Pitrou | 7158e06 | 2011-12-15 16:25:34 +0100 | [diff] [blame] | 1369 | :term:`File objects <file object>` used by the interpreter for standard |
| 1370 | input, output and errors: |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1371 | |
Antoine Pitrou | 7158e06 | 2011-12-15 16:25:34 +0100 | [diff] [blame] | 1372 | * ``stdin`` is used for all interactive input (including calls to |
| 1373 | :func:`input`); |
| 1374 | * ``stdout`` is used for the output of :func:`print` and :term:`expression` |
| 1375 | statements and for the prompts of :func:`input`; |
| 1376 | * The interpreter's own prompts and its error messages go to ``stderr``. |
| 1377 | |
Antoine Pitrou | 2d1ec06 | 2014-05-15 22:38:56 +0200 | [diff] [blame] | 1378 | These streams are regular :term:`text files <text file>` like those |
| 1379 | returned by the :func:`open` function. Their parameters are chosen as |
| 1380 | follows: |
Antoine Pitrou | 7158e06 | 2011-12-15 16:25:34 +0100 | [diff] [blame] | 1381 | |
Lysandros Nikolaou | 5723263 | 2019-02-15 00:35:25 +0100 | [diff] [blame] | 1382 | * The character encoding is platform-dependent. Non-Windows |
| 1383 | platforms use the locale encoding (see |
| 1384 | :meth:`locale.getpreferredencoding()`). |
Antoine Pitrou | 7158e06 | 2011-12-15 16:25:34 +0100 | [diff] [blame] | 1385 | |
Lysandros Nikolaou | 5723263 | 2019-02-15 00:35:25 +0100 | [diff] [blame] | 1386 | On Windows, UTF-8 is used for the console device. Non-character |
| 1387 | devices such as disk files and pipes use the system locale |
| 1388 | encoding (i.e. the ANSI codepage). Non-console character |
| 1389 | devices such as NUL (i.e. where isatty() returns True) use the |
| 1390 | value of the console input and output codepages at startup, |
| 1391 | respectively for stdin and stdout/stderr. This defaults to the |
| 1392 | system locale encoding if the process is not initially attached |
| 1393 | to a console. |
| 1394 | |
| 1395 | The special behaviour of the console can be overridden |
| 1396 | by setting the environment variable PYTHONLEGACYWINDOWSSTDIO |
| 1397 | before starting Python. In that case, the console codepages are |
| 1398 | used as for any other character device. |
| 1399 | |
| 1400 | Under all platforms, you can override the character encoding by |
| 1401 | setting the :envvar:`PYTHONIOENCODING` environment variable before |
| 1402 | starting Python or by using the new :option:`-X` ``utf8`` command |
| 1403 | line option and :envvar:`PYTHONUTF8` environment variable. However, |
| 1404 | for the Windows console, this only applies when |
| 1405 | :envvar:`PYTHONLEGACYWINDOWSSTDIO` is also set. |
Antoine Pitrou | 7158e06 | 2011-12-15 16:25:34 +0100 | [diff] [blame] | 1406 | |
Berker Peksag | 7f58097 | 2017-10-13 15:16:31 +0300 | [diff] [blame] | 1407 | * When interactive, ``stdout`` and ``stderr`` streams are line-buffered. |
| 1408 | Otherwise, they are block-buffered like regular text files. You can |
| 1409 | override this value with the :option:`-u` command-line option. |
Antoine Pitrou | 7158e06 | 2011-12-15 16:25:34 +0100 | [diff] [blame] | 1410 | |
Antoine Pitrou | 2d1ec06 | 2014-05-15 22:38:56 +0200 | [diff] [blame] | 1411 | .. note:: |
Benjamin Peterson | 4199d60 | 2009-05-12 20:47:57 +0000 | [diff] [blame] | 1412 | |
Antoine Pitrou | 2d1ec06 | 2014-05-15 22:38:56 +0200 | [diff] [blame] | 1413 | To write or read binary data from/to the standard streams, use the |
| 1414 | underlying binary :data:`~io.TextIOBase.buffer` object. For example, to |
| 1415 | write bytes to :data:`stdout`, use ``sys.stdout.buffer.write(b'abc')``. |
Benjamin Peterson | 995bb47 | 2009-06-14 18:41:18 +0000 | [diff] [blame] | 1416 | |
Antoine Pitrou | 2d1ec06 | 2014-05-15 22:38:56 +0200 | [diff] [blame] | 1417 | However, if you are writing a library (and do not control in which |
| 1418 | context its code will be executed), be aware that the standard streams |
| 1419 | may be replaced with file-like objects like :class:`io.StringIO` which |
| 1420 | do not support the :attr:`~io.BufferedIOBase.buffer` attribute. |
Benjamin Peterson | eb9fc52 | 2008-12-07 14:58:03 +0000 | [diff] [blame] | 1421 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1422 | |
| 1423 | .. data:: __stdin__ |
| 1424 | __stdout__ |
| 1425 | __stderr__ |
| 1426 | |
| 1427 | These objects contain the original values of ``stdin``, ``stderr`` and |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 1428 | ``stdout`` at the start of the program. They are used during finalization, |
| 1429 | and could be useful to print to the actual standard stream no matter if the |
| 1430 | ``sys.std*`` object has been redirected. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1431 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 1432 | It can also be used to restore the actual files to known working file objects |
| 1433 | in case they have been overwritten with a broken object. However, the |
| 1434 | preferred way to do this is to explicitly save the previous stream before |
| 1435 | replacing it, and restore the saved object. |
Christian Heimes | 58cb1b8 | 2007-11-13 02:19:40 +0000 | [diff] [blame] | 1436 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 1437 | .. note:: |
| 1438 | Under some conditions ``stdin``, ``stdout`` and ``stderr`` as well as the |
| 1439 | original values ``__stdin__``, ``__stdout__`` and ``__stderr__`` can be |
Serhiy Storchaka | ecf41da | 2016-10-19 16:29:26 +0300 | [diff] [blame] | 1440 | ``None``. It is usually the case for Windows GUI apps that aren't connected |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 1441 | to a console and Python apps started with :program:`pythonw`. |
Christian Heimes | 58cb1b8 | 2007-11-13 02:19:40 +0000 | [diff] [blame] | 1442 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1443 | |
Victor Stinner | d5c355c | 2011-04-30 14:53:09 +0200 | [diff] [blame] | 1444 | .. data:: thread_info |
| 1445 | |
| 1446 | A :term:`struct sequence` holding information about the thread |
| 1447 | implementation. |
| 1448 | |
Georg Brandl | 44ea77b | 2013-03-28 13:28:44 +0100 | [diff] [blame] | 1449 | .. tabularcolumns:: |l|p{0.7\linewidth}| |
| 1450 | |
Victor Stinner | d5c355c | 2011-04-30 14:53:09 +0200 | [diff] [blame] | 1451 | +------------------+---------------------------------------------------------+ |
| 1452 | | Attribute | Explanation | |
| 1453 | +==================+=========================================================+ |
| 1454 | | :const:`name` | Name of the thread implementation: | |
| 1455 | | | | |
| 1456 | | | * ``'nt'``: Windows threads | |
Victor Stinner | d5c355c | 2011-04-30 14:53:09 +0200 | [diff] [blame] | 1457 | | | * ``'pthread'``: POSIX threads | |
| 1458 | | | * ``'solaris'``: Solaris threads | |
| 1459 | +------------------+---------------------------------------------------------+ |
| 1460 | | :const:`lock` | Name of the lock implementation: | |
| 1461 | | | | |
| 1462 | | | * ``'semaphore'``: a lock uses a semaphore | |
| 1463 | | | * ``'mutex+cond'``: a lock uses a mutex | |
| 1464 | | | and a condition variable | |
| 1465 | | | * ``None`` if this information is unknown | |
| 1466 | +------------------+---------------------------------------------------------+ |
| 1467 | | :const:`version` | Name and version of the thread library. It is a string, | |
luzpaz | a5293b4 | 2017-11-05 07:37:50 -0600 | [diff] [blame] | 1468 | | | or ``None`` if this information is unknown. | |
Victor Stinner | d5c355c | 2011-04-30 14:53:09 +0200 | [diff] [blame] | 1469 | +------------------+---------------------------------------------------------+ |
| 1470 | |
| 1471 | .. versionadded:: 3.3 |
| 1472 | |
| 1473 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1474 | .. data:: tracebacklimit |
| 1475 | |
| 1476 | When this variable is set to an integer value, it determines the maximum number |
| 1477 | of levels of traceback information printed when an unhandled exception occurs. |
| 1478 | The default is ``1000``. When set to ``0`` or less, all traceback information |
| 1479 | is suppressed and only the exception type and value are printed. |
| 1480 | |
| 1481 | |
Victor Stinner | ef9d9b6 | 2019-05-22 11:28:22 +0200 | [diff] [blame] | 1482 | .. function:: unraisablehook(unraisable, /) |
| 1483 | |
| 1484 | Handle an unraisable exception. |
| 1485 | |
| 1486 | Called when an exception has occurred but there is no way for Python to |
| 1487 | handle it. For example, when a destructor raises an exception or during |
| 1488 | garbage collection (:func:`gc.collect`). |
| 1489 | |
| 1490 | The *unraisable* argument has the following attributes: |
| 1491 | |
| 1492 | * *exc_type*: Exception type. |
| 1493 | * *exc_value*: Exception value, can be ``None``. |
| 1494 | * *exc_traceback*: Exception traceback, can be ``None``. |
Victor Stinner | 71c52e3 | 2019-05-27 08:57:14 +0200 | [diff] [blame] | 1495 | * *err_msg*: Error message, can be ``None``. |
Victor Stinner | ef9d9b6 | 2019-05-22 11:28:22 +0200 | [diff] [blame] | 1496 | * *object*: Object causing the exception, can be ``None``. |
| 1497 | |
Victor Stinner | 71c52e3 | 2019-05-27 08:57:14 +0200 | [diff] [blame] | 1498 | The default hook formats *err_msg* and *object* as: |
| 1499 | ``f'{err_msg}: {object!r}'``; use "Exception ignored in" error message |
| 1500 | if *err_msg* is ``None``. |
| 1501 | |
Victor Stinner | 212646c | 2019-06-14 18:03:22 +0200 | [diff] [blame] | 1502 | :func:`sys.unraisablehook` can be overridden to control how unraisable |
| 1503 | exceptions are handled. |
| 1504 | |
| 1505 | Storing *exc_value* using a custom hook can create a reference cycle. It |
| 1506 | should be cleared explicitly to break the reference cycle when the |
| 1507 | exception is no longer needed. |
| 1508 | |
| 1509 | Storing *object* using a custom hook can resurrect it if it is set to an |
| 1510 | object which is being finalized. Avoid storing *object* after the custom |
| 1511 | hook completes to avoid resurrecting objects. |
| 1512 | |
Victor Stinner | ef9d9b6 | 2019-05-22 11:28:22 +0200 | [diff] [blame] | 1513 | See also :func:`excepthook` which handles uncaught exceptions. |
| 1514 | |
| 1515 | .. versionadded:: 3.8 |
| 1516 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1517 | .. data:: version |
| 1518 | |
| 1519 | A string containing the version number of the Python interpreter plus additional |
Georg Brandl | e42a59d | 2010-07-31 20:05:31 +0000 | [diff] [blame] | 1520 | information on the build number and compiler used. This string is displayed |
| 1521 | when the interactive interpreter is started. Do not extract version information |
| 1522 | out of it, rather, use :data:`version_info` and the functions provided by the |
| 1523 | :mod:`platform` module. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1524 | |
| 1525 | |
| 1526 | .. data:: api_version |
| 1527 | |
| 1528 | The C API version for this interpreter. Programmers may find this useful when |
| 1529 | debugging version conflicts between Python and extension modules. |
| 1530 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1531 | |
| 1532 | .. data:: version_info |
| 1533 | |
| 1534 | A tuple containing the five components of the version number: *major*, *minor*, |
| 1535 | *micro*, *releaselevel*, and *serial*. All values except *releaselevel* are |
| 1536 | integers; the release level is ``'alpha'``, ``'beta'``, ``'candidate'``, or |
| 1537 | ``'final'``. The ``version_info`` value corresponding to the Python version 2.0 |
Eric Smith | 0e5b562 | 2009-02-06 01:32:42 +0000 | [diff] [blame] | 1538 | is ``(2, 0, 0, 'final', 0)``. The components can also be accessed by name, |
| 1539 | so ``sys.version_info[0]`` is equivalent to ``sys.version_info.major`` |
| 1540 | and so on. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1541 | |
Raymond Hettinger | 35a8836 | 2009-04-09 00:08:24 +0000 | [diff] [blame] | 1542 | .. versionchanged:: 3.1 |
Georg Brandl | 67b21b7 | 2010-08-17 15:07:14 +0000 | [diff] [blame] | 1543 | Added named component attributes. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1544 | |
| 1545 | .. data:: warnoptions |
| 1546 | |
| 1547 | This is an implementation detail of the warnings framework; do not modify this |
| 1548 | value. Refer to the :mod:`warnings` module for more information on the warnings |
| 1549 | framework. |
| 1550 | |
| 1551 | |
| 1552 | .. data:: winver |
| 1553 | |
| 1554 | The version number used to form registry keys on Windows platforms. This is |
| 1555 | stored as string resource 1000 in the Python DLL. The value is normally the |
| 1556 | first three characters of :const:`version`. It is provided in the :mod:`sys` |
| 1557 | module for informational purposes; modifying this value has no effect on the |
Cheryl Sabella | 2d6097d | 2018-10-12 10:55:20 -0400 | [diff] [blame] | 1558 | registry keys used by Python. |
| 1559 | |
| 1560 | .. availability:: Windows. |
Mark Dickinson | be5846b | 2010-07-02 20:26:07 +0000 | [diff] [blame] | 1561 | |
Antoine Pitrou | 9583cac | 2010-10-21 13:42:28 +0000 | [diff] [blame] | 1562 | |
| 1563 | .. data:: _xoptions |
| 1564 | |
| 1565 | A dictionary of the various implementation-specific flags passed through |
| 1566 | the :option:`-X` command-line option. Option names are either mapped to |
Martin Panter | 1050d2d | 2016-07-26 11:18:21 +0200 | [diff] [blame] | 1567 | their values, if given explicitly, or to :const:`True`. Example: |
| 1568 | |
| 1569 | .. code-block:: shell-session |
Antoine Pitrou | 9583cac | 2010-10-21 13:42:28 +0000 | [diff] [blame] | 1570 | |
| 1571 | $ ./python -Xa=b -Xc |
| 1572 | Python 3.2a3+ (py3k, Oct 16 2010, 20:14:50) |
| 1573 | [GCC 4.4.3] on linux2 |
| 1574 | Type "help", "copyright", "credits" or "license" for more information. |
| 1575 | >>> import sys |
| 1576 | >>> sys._xoptions |
| 1577 | {'a': 'b', 'c': True} |
| 1578 | |
| 1579 | .. impl-detail:: |
| 1580 | |
| 1581 | This is a CPython-specific way of accessing options passed through |
| 1582 | :option:`-X`. Other implementations may export them through other |
| 1583 | means, or not at all. |
| 1584 | |
| 1585 | .. versionadded:: 3.2 |
| 1586 | |
| 1587 | |
Mark Dickinson | be5846b | 2010-07-02 20:26:07 +0000 | [diff] [blame] | 1588 | .. rubric:: Citations |
| 1589 | |
Serhiy Storchaka | a4d170d | 2013-12-23 18:20:51 +0200 | [diff] [blame] | 1590 | .. [C99] ISO/IEC 9899:1999. "Programming languages -- C." A public draft of this standard is available at http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf\ . |