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 | |
| 19 | .. versionadded:: 3.2 |
| 20 | |
Georg Brandl | df48b97 | 2014-03-24 09:06:18 +0100 | [diff] [blame] | 21 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 22 | .. data:: argv |
| 23 | |
| 24 | The list of command line arguments passed to a Python script. ``argv[0]`` is the |
| 25 | script name (it is operating system dependent whether this is a full pathname or |
| 26 | not). If the command was executed using the :option:`-c` command line option to |
| 27 | the interpreter, ``argv[0]`` is set to the string ``'-c'``. If no script name |
| 28 | was passed to the Python interpreter, ``argv[0]`` is the empty string. |
| 29 | |
| 30 | To loop over the standard input, or the list of files given on the |
| 31 | command line, see the :mod:`fileinput` module. |
| 32 | |
| 33 | |
Vinay Sajip | 7ded1f0 | 2012-05-26 03:45:29 +0100 | [diff] [blame] | 34 | .. data:: base_exec_prefix |
| 35 | |
| 36 | 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] | 37 | :data:`exec_prefix`. If not running in a |
| 38 | :ref:`virtual environment <venv-def>`, the values will stay the same; if |
| 39 | ``site.py`` finds that a virtual environment is in use, the values of |
| 40 | :data:`prefix` and :data:`exec_prefix` will be changed to point to the |
| 41 | virtual environment, whereas :data:`base_prefix` and |
Vinay Sajip | 7ded1f0 | 2012-05-26 03:45:29 +0100 | [diff] [blame] | 42 | :data:`base_exec_prefix` will remain pointing to the base Python |
| 43 | installation (the one which the virtual environment was created from). |
| 44 | |
Georg Brandl | 039b01d | 2012-05-26 09:11:22 +0200 | [diff] [blame] | 45 | .. versionadded:: 3.3 |
| 46 | |
| 47 | |
Vinay Sajip | 7ded1f0 | 2012-05-26 03:45:29 +0100 | [diff] [blame] | 48 | .. data:: base_prefix |
| 49 | |
| 50 | 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] | 51 | :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] | 52 | will stay the same; if ``site.py`` finds that a virtual environment is in |
| 53 | use, the values of :data:`prefix` and :data:`exec_prefix` will be changed to |
| 54 | point to the virtual environment, whereas :data:`base_prefix` and |
| 55 | :data:`base_exec_prefix` will remain pointing to the base Python |
| 56 | installation (the one which the virtual environment was created from). |
| 57 | |
Georg Brandl | 039b01d | 2012-05-26 09:11:22 +0200 | [diff] [blame] | 58 | .. versionadded:: 3.3 |
| 59 | |
| 60 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 61 | .. data:: byteorder |
| 62 | |
| 63 | An indicator of the native byte order. This will have the value ``'big'`` on |
| 64 | big-endian (most-significant byte first) platforms, and ``'little'`` on |
| 65 | little-endian (least-significant byte first) platforms. |
| 66 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 67 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 68 | .. data:: builtin_module_names |
| 69 | |
| 70 | A tuple of strings giving the names of all modules that are compiled into this |
| 71 | Python interpreter. (This information is not available in any other way --- |
| 72 | ``modules.keys()`` only lists the imported modules.) |
| 73 | |
| 74 | |
Georg Brandl | 8527126 | 2010-10-17 11:06:14 +0000 | [diff] [blame] | 75 | .. function:: call_tracing(func, args) |
| 76 | |
| 77 | Call ``func(*args)``, while tracing is enabled. The tracing state is saved, |
| 78 | and restored afterwards. This is intended to be called from a debugger from |
| 79 | a checkpoint, to recursively debug some other code. |
| 80 | |
| 81 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 82 | .. data:: copyright |
| 83 | |
| 84 | A string containing the copyright pertaining to the Python interpreter. |
| 85 | |
| 86 | |
Christian Heimes | 15ebc88 | 2008-02-04 18:48:49 +0000 | [diff] [blame] | 87 | .. function:: _clear_type_cache() |
| 88 | |
| 89 | Clear the internal type cache. The type cache is used to speed up attribute |
| 90 | and method lookups. Use the function *only* to drop unnecessary references |
| 91 | during reference leak debugging. |
| 92 | |
| 93 | This function should be used for internal and specialized purposes only. |
Christian Heimes | 2685563 | 2008-01-27 23:50:43 +0000 | [diff] [blame] | 94 | |
Christian Heimes | 2685563 | 2008-01-27 23:50:43 +0000 | [diff] [blame] | 95 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 96 | .. function:: _current_frames() |
| 97 | |
| 98 | Return a dictionary mapping each thread's identifier to the topmost stack frame |
| 99 | currently active in that thread at the time the function is called. Note that |
| 100 | functions in the :mod:`traceback` module can build the call stack given such a |
| 101 | frame. |
| 102 | |
| 103 | This is most useful for debugging deadlock: this function does not require the |
| 104 | deadlocked threads' cooperation, and such threads' call stacks are frozen for as |
| 105 | long as they remain deadlocked. The frame returned for a non-deadlocked thread |
| 106 | may bear no relationship to that thread's current activity by the time calling |
| 107 | code examines the frame. |
| 108 | |
| 109 | This function should be used for internal and specialized purposes only. |
| 110 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 111 | |
David Malcolm | 49526f4 | 2012-06-22 14:55:41 -0400 | [diff] [blame] | 112 | .. function:: _debugmallocstats() |
| 113 | |
| 114 | Print low-level information to stderr about the state of CPython's memory |
| 115 | allocator. |
| 116 | |
| 117 | If Python is configured --with-pydebug, it also performs some expensive |
| 118 | internal consistency checks. |
| 119 | |
| 120 | .. versionadded:: 3.3 |
| 121 | |
| 122 | .. impl-detail:: |
| 123 | |
| 124 | This function is specific to CPython. The exact output format is not |
| 125 | defined here, and may change. |
| 126 | |
| 127 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 128 | .. data:: dllhandle |
| 129 | |
| 130 | Integer specifying the handle of the Python DLL. Availability: Windows. |
| 131 | |
| 132 | |
| 133 | .. function:: displayhook(value) |
| 134 | |
Victor Stinner | 13d49ee | 2010-12-04 17:24:33 +0000 | [diff] [blame] | 135 | If *value* is not ``None``, this function prints ``repr(value)`` to |
| 136 | ``sys.stdout``, and saves *value* in ``builtins._``. If ``repr(value)`` is |
| 137 | not encodable to ``sys.stdout.encoding`` with ``sys.stdout.errors`` error |
| 138 | handler (which is probably ``'strict'``), encode it to |
| 139 | ``sys.stdout.encoding`` with ``'backslashreplace'`` error handler. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 140 | |
Christian Heimes | d8654cf | 2007-12-02 15:22:16 +0000 | [diff] [blame] | 141 | ``sys.displayhook`` is called on the result of evaluating an :term:`expression` |
| 142 | entered in an interactive Python session. The display of these values can be |
| 143 | customized by assigning another one-argument function to ``sys.displayhook``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 144 | |
Victor Stinner | 13d49ee | 2010-12-04 17:24:33 +0000 | [diff] [blame] | 145 | Pseudo-code:: |
| 146 | |
| 147 | def displayhook(value): |
| 148 | if value is None: |
| 149 | return |
| 150 | # Set '_' to None to avoid recursion |
| 151 | builtins._ = None |
| 152 | text = repr(value) |
| 153 | try: |
| 154 | sys.stdout.write(text) |
| 155 | except UnicodeEncodeError: |
| 156 | bytes = text.encode(sys.stdout.encoding, 'backslashreplace') |
| 157 | if hasattr(sys.stdout, 'buffer'): |
| 158 | sys.stdout.buffer.write(bytes) |
| 159 | else: |
| 160 | text = bytes.decode(sys.stdout.encoding, 'strict') |
| 161 | sys.stdout.write(text) |
| 162 | sys.stdout.write("\n") |
| 163 | builtins._ = value |
| 164 | |
| 165 | .. versionchanged:: 3.2 |
| 166 | Use ``'backslashreplace'`` error handler on :exc:`UnicodeEncodeError`. |
| 167 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 168 | |
Éric Araujo | da27263 | 2011-10-05 01:17:38 +0200 | [diff] [blame] | 169 | .. data:: dont_write_bytecode |
| 170 | |
Brett Cannon | f299abd | 2015-04-13 14:21:02 -0400 | [diff] [blame] | 171 | 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] | 172 | import of source modules. This value is initially set to ``True`` or |
| 173 | ``False`` depending on the :option:`-B` command line option and the |
| 174 | :envvar:`PYTHONDONTWRITEBYTECODE` environment variable, but you can set it |
| 175 | yourself to control bytecode file generation. |
| 176 | |
| 177 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 178 | .. function:: excepthook(type, value, traceback) |
| 179 | |
| 180 | This function prints out a given traceback and exception to ``sys.stderr``. |
| 181 | |
| 182 | When an exception is raised and uncaught, the interpreter calls |
| 183 | ``sys.excepthook`` with three arguments, the exception class, exception |
| 184 | instance, and a traceback object. In an interactive session this happens just |
| 185 | before control is returned to the prompt; in a Python program this happens just |
| 186 | before the program exits. The handling of such top-level exceptions can be |
| 187 | customized by assigning another three-argument function to ``sys.excepthook``. |
| 188 | |
| 189 | |
| 190 | .. data:: __displayhook__ |
| 191 | __excepthook__ |
| 192 | |
| 193 | These objects contain the original values of ``displayhook`` and ``excepthook`` |
| 194 | at the start of the program. They are saved so that ``displayhook`` and |
| 195 | ``excepthook`` can be restored in case they happen to get replaced with broken |
| 196 | objects. |
| 197 | |
| 198 | |
| 199 | .. function:: exc_info() |
| 200 | |
| 201 | This function returns a tuple of three values that give information about the |
| 202 | exception that is currently being handled. The information returned is specific |
| 203 | both to the current thread and to the current stack frame. If the current stack |
| 204 | frame is not handling an exception, the information is taken from the calling |
| 205 | stack frame, or its caller, and so on until a stack frame is found that is |
| 206 | handling an exception. Here, "handling an exception" is defined as "executing |
Benjamin Peterson | eec3d71 | 2008-06-11 15:59:43 +0000 | [diff] [blame] | 207 | an except clause." For any stack frame, only information about the exception |
| 208 | being currently handled is accessible. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 209 | |
| 210 | .. index:: object: traceback |
| 211 | |
Georg Brandl | 482b151 | 2010-03-21 09:02:59 +0000 | [diff] [blame] | 212 | If no exception is being handled anywhere on the stack, a tuple containing |
| 213 | three ``None`` values is returned. Otherwise, the values returned are |
| 214 | ``(type, value, traceback)``. Their meaning is: *type* gets the type of the |
| 215 | exception being handled (a subclass of :exc:`BaseException`); *value* gets |
| 216 | the exception instance (an instance of the exception type); *traceback* gets |
| 217 | a traceback object (see the Reference Manual) which encapsulates the call |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 218 | stack at the point where the exception originally occurred. |
| 219 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 220 | |
| 221 | .. data:: exec_prefix |
| 222 | |
| 223 | A string giving the site-specific directory prefix where the platform-dependent |
| 224 | 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] | 225 | be set at build time with the ``--exec-prefix`` argument to the |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 226 | :program:`configure` script. Specifically, all configuration files (e.g. the |
Éric Araujo | 58a9153 | 2011-10-05 01:28:24 +0200 | [diff] [blame] | 227 | :file:`pyconfig.h` header file) are installed in the directory |
Georg Brandl | eb25fb7 | 2012-02-23 21:12:39 +0100 | [diff] [blame] | 228 | :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] | 229 | installed in :file:`{exec_prefix}/lib/python{X.Y}/lib-dynload`, where *X.Y* |
| 230 | is the version number of Python, for example ``3.2``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 231 | |
Larry Hastings | 3732ed2 | 2014-03-15 21:13:56 -0700 | [diff] [blame] | 232 | .. note:: |
| 233 | |
| 234 | If a :ref:`virtual environment <venv-def>` is in effect, this |
Vinay Sajip | cd9b746 | 2012-07-09 10:37:01 +0100 | [diff] [blame] | 235 | value will be changed in ``site.py`` to point to the virtual environment. |
| 236 | The value for the Python installation will still be available, via |
| 237 | :data:`base_exec_prefix`. |
Vinay Sajip | 7ded1f0 | 2012-05-26 03:45:29 +0100 | [diff] [blame] | 238 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 239 | |
| 240 | .. data:: executable |
| 241 | |
Petri Lehtinen | 9713321 | 2012-02-02 20:59:48 +0200 | [diff] [blame] | 242 | A string giving the absolute path of the executable binary for the Python |
| 243 | interpreter, on systems where this makes sense. If Python is unable to retrieve |
| 244 | the real path to its executable, :data:`sys.executable` will be an empty string |
| 245 | or ``None``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 246 | |
| 247 | |
| 248 | .. function:: exit([arg]) |
| 249 | |
| 250 | Exit from Python. This is implemented by raising the :exc:`SystemExit` |
| 251 | exception, so cleanup actions specified by finally clauses of :keyword:`try` |
Georg Brandl | 6f4e68d | 2010-10-17 10:51:45 +0000 | [diff] [blame] | 252 | statements are honored, and it is possible to intercept the exit attempt at |
| 253 | an outer level. |
| 254 | |
| 255 | The optional argument *arg* can be an integer giving the exit status |
| 256 | (defaulting to zero), or another type of object. If it is an integer, zero |
| 257 | is considered "successful termination" and any nonzero value is considered |
| 258 | "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] | 259 | in the range 0--127, and produce undefined results otherwise. Some systems |
Georg Brandl | 6f4e68d | 2010-10-17 10:51:45 +0000 | [diff] [blame] | 260 | have a convention for assigning specific meanings to specific exit codes, but |
| 261 | these are generally underdeveloped; Unix programs generally use 2 for command |
| 262 | line syntax errors and 1 for all other kind of errors. If another type of |
| 263 | object is passed, ``None`` is equivalent to passing zero, and any other |
| 264 | object is printed to :data:`stderr` and results in an exit code of 1. In |
| 265 | particular, ``sys.exit("some error message")`` is a quick way to exit a |
| 266 | program when an error occurs. |
| 267 | |
| 268 | Since :func:`exit` ultimately "only" raises an exception, it will only exit |
| 269 | the process when called from the main thread, and the exception is not |
| 270 | intercepted. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 271 | |
Martin Panter | b4ce1fc | 2015-11-30 03:18:29 +0000 | [diff] [blame] | 272 | .. versionchanged:: 3.6 |
| 273 | If an error occurs in the cleanup after the Python interpreter |
| 274 | has caught :exc:`SystemExit` (such as an error flushing buffered data |
| 275 | in the standard streams), the exit status is changed to 120. |
| 276 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 277 | |
Christian Heimes | d32ed6f | 2008-01-14 18:49:24 +0000 | [diff] [blame] | 278 | .. data:: flags |
| 279 | |
Benjamin Peterson | 2b8ef2d | 2011-04-20 18:31:22 -0500 | [diff] [blame] | 280 | The :term:`struct sequence` *flags* exposes the status of command line |
| 281 | flags. The attributes are read only. |
Christian Heimes | d32ed6f | 2008-01-14 18:49:24 +0000 | [diff] [blame] | 282 | |
Éric Araujo | 5ab4776 | 2011-03-26 00:47:04 +0100 | [diff] [blame] | 283 | ============================= ============================= |
| 284 | attribute flag |
| 285 | ============================= ============================= |
| 286 | :const:`debug` :option:`-d` |
Éric Araujo | 5ab4776 | 2011-03-26 00:47:04 +0100 | [diff] [blame] | 287 | :const:`inspect` :option:`-i` |
| 288 | :const:`interactive` :option:`-i` |
| 289 | :const:`optimize` :option:`-O` or :option:`-OO` |
| 290 | :const:`dont_write_bytecode` :option:`-B` |
| 291 | :const:`no_user_site` :option:`-s` |
| 292 | :const:`no_site` :option:`-S` |
| 293 | :const:`ignore_environment` :option:`-E` |
| 294 | :const:`verbose` :option:`-v` |
| 295 | :const:`bytes_warning` :option:`-b` |
Éric Araujo | 722bec4 | 2011-03-26 01:59:47 +0100 | [diff] [blame] | 296 | :const:`quiet` :option:`-q` |
Georg Brandl | 2daf6ae | 2012-02-20 19:54:16 +0100 | [diff] [blame] | 297 | :const:`hash_randomization` :option:`-R` |
Éric Araujo | 5ab4776 | 2011-03-26 00:47:04 +0100 | [diff] [blame] | 298 | ============================= ============================= |
Georg Brandl | 8aa7e99 | 2010-12-28 18:30:18 +0000 | [diff] [blame] | 299 | |
| 300 | .. versionchanged:: 3.2 |
| 301 | Added ``quiet`` attribute for the new :option:`-q` flag. |
Christian Heimes | d32ed6f | 2008-01-14 18:49:24 +0000 | [diff] [blame] | 302 | |
Georg Brandl | 09a7c72 | 2012-02-20 21:31:46 +0100 | [diff] [blame] | 303 | .. versionadded:: 3.2.3 |
Georg Brandl | 2daf6ae | 2012-02-20 19:54:16 +0100 | [diff] [blame] | 304 | The ``hash_randomization`` attribute. |
| 305 | |
Éric Araujo | 3e89870 | 2011-04-24 04:37:00 +0200 | [diff] [blame] | 306 | .. versionchanged:: 3.3 |
| 307 | Removed obsolete ``division_warning`` attribute. |
| 308 | |
Christian Heimes | d32ed6f | 2008-01-14 18:49:24 +0000 | [diff] [blame] | 309 | |
Christian Heimes | 9385266 | 2007-12-01 12:22:32 +0000 | [diff] [blame] | 310 | .. data:: float_info |
| 311 | |
Benjamin Peterson | 2b8ef2d | 2011-04-20 18:31:22 -0500 | [diff] [blame] | 312 | A :term:`struct sequence` holding information about the float type. It |
| 313 | contains low level information about the precision and internal |
| 314 | representation. The values correspond to the various floating-point |
| 315 | constants defined in the standard header file :file:`float.h` for the 'C' |
| 316 | programming language; see section 5.2.4.2.2 of the 1999 ISO/IEC C standard |
| 317 | [C99]_, 'Characteristics of floating types', for details. |
Christian Heimes | 9385266 | 2007-12-01 12:22:32 +0000 | [diff] [blame] | 318 | |
Georg Brandl | 44ea77b | 2013-03-28 13:28:44 +0100 | [diff] [blame] | 319 | .. tabularcolumns:: |l|l|L| |
| 320 | |
Mark Dickinson | be5846b | 2010-07-02 20:26:07 +0000 | [diff] [blame] | 321 | +---------------------+----------------+--------------------------------------------------+ |
| 322 | | attribute | float.h macro | explanation | |
| 323 | +=====================+================+==================================================+ |
Mark Dickinson | 39af05f | 2010-07-03 09:17:16 +0000 | [diff] [blame] | 324 | | :const:`epsilon` | DBL_EPSILON | difference between 1 and the least value greater | |
Mark Dickinson | be5846b | 2010-07-02 20:26:07 +0000 | [diff] [blame] | 325 | | | | than 1 that is representable as a float | |
| 326 | +---------------------+----------------+--------------------------------------------------+ |
| 327 | | :const:`dig` | DBL_DIG | maximum number of decimal digits that can be | |
| 328 | | | | faithfully represented in a float; see below | |
| 329 | +---------------------+----------------+--------------------------------------------------+ |
| 330 | | :const:`mant_dig` | DBL_MANT_DIG | float precision: the number of base-``radix`` | |
| 331 | | | | digits in the significand of a float | |
| 332 | +---------------------+----------------+--------------------------------------------------+ |
| 333 | | :const:`max` | DBL_MAX | maximum representable finite float | |
| 334 | +---------------------+----------------+--------------------------------------------------+ |
| 335 | | :const:`max_exp` | DBL_MAX_EXP | maximum integer e such that ``radix**(e-1)`` is | |
| 336 | | | | a representable finite float | |
| 337 | +---------------------+----------------+--------------------------------------------------+ |
| 338 | | :const:`max_10_exp` | DBL_MAX_10_EXP | maximum integer e such that ``10**e`` is in the | |
| 339 | | | | range of representable finite floats | |
| 340 | +---------------------+----------------+--------------------------------------------------+ |
| 341 | | :const:`min` | DBL_MIN | minimum positive normalized float | |
| 342 | +---------------------+----------------+--------------------------------------------------+ |
| 343 | | :const:`min_exp` | DBL_MIN_EXP | minimum integer e such that ``radix**(e-1)`` is | |
| 344 | | | | a normalized float | |
| 345 | +---------------------+----------------+--------------------------------------------------+ |
| 346 | | :const:`min_10_exp` | DBL_MIN_10_EXP | minimum integer e such that ``10**e`` is a | |
| 347 | | | | normalized float | |
| 348 | +---------------------+----------------+--------------------------------------------------+ |
| 349 | | :const:`radix` | FLT_RADIX | radix of exponent representation | |
| 350 | +---------------------+----------------+--------------------------------------------------+ |
Mark Dickinson | b1e58fe | 2011-11-19 16:26:45 +0000 | [diff] [blame] | 351 | | :const:`rounds` | FLT_ROUNDS | integer constant representing the rounding mode | |
| 352 | | | | used for arithmetic operations. This reflects | |
| 353 | | | | the value of the system FLT_ROUNDS macro at | |
| 354 | | | | interpreter startup time. See section 5.2.4.2.2 | |
| 355 | | | | of the C99 standard for an explanation of the | |
| 356 | | | | possible values and their meanings. | |
Mark Dickinson | be5846b | 2010-07-02 20:26:07 +0000 | [diff] [blame] | 357 | +---------------------+----------------+--------------------------------------------------+ |
Christian Heimes | 9385266 | 2007-12-01 12:22:32 +0000 | [diff] [blame] | 358 | |
Mark Dickinson | be5846b | 2010-07-02 20:26:07 +0000 | [diff] [blame] | 359 | The attribute :attr:`sys.float_info.dig` needs further explanation. If |
| 360 | ``s`` is any string representing a decimal number with at most |
| 361 | :attr:`sys.float_info.dig` significant digits, then converting ``s`` to a |
| 362 | float and back again will recover a string representing the same decimal |
| 363 | value:: |
Christian Heimes | 9385266 | 2007-12-01 12:22:32 +0000 | [diff] [blame] | 364 | |
Mark Dickinson | be5846b | 2010-07-02 20:26:07 +0000 | [diff] [blame] | 365 | >>> import sys |
| 366 | >>> sys.float_info.dig |
| 367 | 15 |
| 368 | >>> s = '3.14159265358979' # decimal string with 15 significant digits |
| 369 | >>> format(float(s), '.15g') # convert to float and back -> same value |
| 370 | '3.14159265358979' |
Christian Heimes | 9385266 | 2007-12-01 12:22:32 +0000 | [diff] [blame] | 371 | |
Mark Dickinson | be5846b | 2010-07-02 20:26:07 +0000 | [diff] [blame] | 372 | But for strings with more than :attr:`sys.float_info.dig` significant digits, |
| 373 | this isn't always true:: |
| 374 | |
| 375 | >>> s = '9876543211234567' # 16 significant digits is too many! |
| 376 | >>> format(float(s), '.16g') # conversion changes value |
| 377 | '9876543211234568' |
Christian Heimes | 9385266 | 2007-12-01 12:22:32 +0000 | [diff] [blame] | 378 | |
Mark Dickinson | b08a53a | 2009-04-16 19:52:09 +0000 | [diff] [blame] | 379 | .. data:: float_repr_style |
| 380 | |
| 381 | A string indicating how the :func:`repr` function behaves for |
| 382 | floats. If the string has value ``'short'`` then for a finite |
| 383 | float ``x``, ``repr(x)`` aims to produce a short string with the |
| 384 | property that ``float(repr(x)) == x``. This is the usual behaviour |
| 385 | in Python 3.1 and later. Otherwise, ``float_repr_style`` has value |
| 386 | ``'legacy'`` and ``repr(x)`` behaves in the same way as it did in |
| 387 | versions of Python prior to 3.1. |
| 388 | |
| 389 | .. versionadded:: 3.1 |
| 390 | |
| 391 | |
Antoine Pitrou | f9d0b12 | 2012-12-09 14:28:26 +0100 | [diff] [blame] | 392 | .. function:: getallocatedblocks() |
| 393 | |
| 394 | Return the number of memory blocks currently allocated by the interpreter, |
Antoine Pitrou | 9284053 | 2012-12-17 23:05:59 +0100 | [diff] [blame] | 395 | regardless of their size. This function is mainly useful for tracking |
| 396 | and debugging memory leaks. Because of the interpreter's internal |
| 397 | caches, the result can vary from call to call; you may have to call |
| 398 | :func:`_clear_type_cache()` and :func:`gc.collect()` to get more |
| 399 | predictable results. |
| 400 | |
| 401 | If a Python build or implementation cannot reasonably compute this |
| 402 | information, :func:`getallocatedblocks()` is allowed to return 0 instead. |
Antoine Pitrou | f9d0b12 | 2012-12-09 14:28:26 +0100 | [diff] [blame] | 403 | |
| 404 | .. versionadded:: 3.4 |
| 405 | |
Antoine Pitrou | f9d0b12 | 2012-12-09 14:28:26 +0100 | [diff] [blame] | 406 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 407 | .. function:: getcheckinterval() |
| 408 | |
| 409 | Return the interpreter's "check interval"; see :func:`setcheckinterval`. |
| 410 | |
Antoine Pitrou | d42bc51 | 2009-11-10 23:18:31 +0000 | [diff] [blame] | 411 | .. deprecated:: 3.2 |
| 412 | Use :func:`getswitchinterval` instead. |
| 413 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 414 | |
| 415 | .. function:: getdefaultencoding() |
| 416 | |
| 417 | Return the name of the current default string encoding used by the Unicode |
| 418 | implementation. |
| 419 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 420 | |
| 421 | .. function:: getdlopenflags() |
| 422 | |
Andrew Kuchling | c61b913 | 2013-06-21 10:58:41 -0400 | [diff] [blame] | 423 | Return the current value of the flags that are used for |
| 424 | :c:func:`dlopen` calls. Symbolic names for the flag values can be |
| 425 | found in the :mod:`os` module (``RTLD_xxx`` constants, e.g. |
| 426 | :data:`os.RTLD_LAZY`). Availability: Unix. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 427 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 428 | |
| 429 | .. function:: getfilesystemencoding() |
| 430 | |
Steve Dower | cc16be8 | 2016-09-08 10:35:16 -0700 | [diff] [blame] | 431 | Return the name of the encoding used to convert between Unicode |
| 432 | filenames and bytes filenames. For best compatibility, str should be |
| 433 | used for filenames in all cases, although representing filenames as bytes |
| 434 | is also supported. Functions accepting or returning filenames should support |
| 435 | either str or bytes and internally convert to the system's preferred |
| 436 | representation. |
| 437 | |
| 438 | This encoding is always ASCII-compatible. |
| 439 | |
| 440 | :func:`os.fsencode` and :func:`os.fsdecode` should be used to ensure that |
| 441 | the correct encoding and errors mode are used. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 442 | |
Ezio Melotti | d5334e1 | 2010-04-29 16:24:51 +0000 | [diff] [blame] | 443 | * On Mac OS X, the encoding is ``'utf-8'``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 444 | |
Steve Dower | cc16be8 | 2016-09-08 10:35:16 -0700 | [diff] [blame] | 445 | * On Unix, the encoding is the locale encoding. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 446 | |
Steve Dower | cc16be8 | 2016-09-08 10:35:16 -0700 | [diff] [blame] | 447 | * On Windows, the encoding may be ``'utf-8'`` or ``'mbcs'``, depending |
| 448 | on user configuration. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 449 | |
Victor Stinner | b744ba1 | 2010-05-15 12:27:16 +0000 | [diff] [blame] | 450 | .. versionchanged:: 3.2 |
Victor Stinner | 22d0418 | 2013-12-02 12:16:46 +0100 | [diff] [blame] | 451 | :func:`getfilesystemencoding` result cannot be ``None`` anymore. |
Victor Stinner | b744ba1 | 2010-05-15 12:27:16 +0000 | [diff] [blame] | 452 | |
Steve Dower | cc16be8 | 2016-09-08 10:35:16 -0700 | [diff] [blame] | 453 | .. versionchanged:: 3.6 |
| 454 | Windows is no longer guaranteed to return ``'mbcs'``. See :pep:`529` |
| 455 | and :func:`_enablelegacywindowsfsencoding` for more information. |
| 456 | |
| 457 | .. function:: getfilesystemencodeerrors() |
| 458 | |
| 459 | Return the name of the error mode used to convert between Unicode filenames |
| 460 | and bytes filenames. The encoding name is returned from |
| 461 | :func:`getfilesystemencoding`. |
| 462 | |
| 463 | :func:`os.fsencode` and :func:`os.fsdecode` should be used to ensure that |
| 464 | the correct encoding and errors mode are used. |
| 465 | |
| 466 | .. versionadded:: 3.6 |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 467 | |
| 468 | .. function:: getrefcount(object) |
| 469 | |
| 470 | Return the reference count of the *object*. The count returned is generally one |
| 471 | higher than you might expect, because it includes the (temporary) reference as |
| 472 | an argument to :func:`getrefcount`. |
| 473 | |
| 474 | |
| 475 | .. function:: getrecursionlimit() |
| 476 | |
| 477 | Return the current value of the recursion limit, the maximum depth of the Python |
| 478 | interpreter stack. This limit prevents infinite recursion from causing an |
| 479 | overflow of the C stack and crashing Python. It can be set by |
| 480 | :func:`setrecursionlimit`. |
| 481 | |
| 482 | |
Robert Schuppenies | fbe94c5 | 2008-07-14 10:13:31 +0000 | [diff] [blame] | 483 | .. function:: getsizeof(object[, default]) |
Martin v. Löwis | 00709aa | 2008-06-04 14:18:43 +0000 | [diff] [blame] | 484 | |
| 485 | Return the size of an object in bytes. The object can be any type of |
| 486 | object. All built-in objects will return correct results, but this |
Robert Schuppenies | fbe94c5 | 2008-07-14 10:13:31 +0000 | [diff] [blame] | 487 | 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] | 488 | specific. |
| 489 | |
Martin v. Löwis | 1e5d0ff | 2012-06-17 10:40:16 +0200 | [diff] [blame] | 490 | Only the memory consumption directly attributed to the object is |
| 491 | accounted for, not the memory consumption of objects it refers to. |
| 492 | |
Benjamin Peterson | 4ac9ce4 | 2009-10-04 14:49:41 +0000 | [diff] [blame] | 493 | 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] | 494 | retrieve the size. Otherwise a :exc:`TypeError` will be raised. |
Robert Schuppenies | fbe94c5 | 2008-07-14 10:13:31 +0000 | [diff] [blame] | 495 | |
Benjamin Peterson | 4ac9ce4 | 2009-10-04 14:49:41 +0000 | [diff] [blame] | 496 | :func:`getsizeof` calls the object's ``__sizeof__`` method and adds an |
| 497 | additional garbage collector overhead if the object is managed by the garbage |
| 498 | collector. |
Robert Schuppenies | fbe94c5 | 2008-07-14 10:13:31 +0000 | [diff] [blame] | 499 | |
Serhiy Storchaka | 6dff020 | 2016-05-07 10:49:07 +0300 | [diff] [blame] | 500 | See `recursive sizeof recipe <https://code.activestate.com/recipes/577504>`_ |
Raymond Hettinger | c539a2a | 2010-12-17 23:31:30 +0000 | [diff] [blame] | 501 | for an example of using :func:`getsizeof` recursively to find the size of |
| 502 | containers and all their contents. |
Martin v. Löwis | 00709aa | 2008-06-04 14:18:43 +0000 | [diff] [blame] | 503 | |
Antoine Pitrou | d42bc51 | 2009-11-10 23:18:31 +0000 | [diff] [blame] | 504 | .. function:: getswitchinterval() |
| 505 | |
| 506 | Return the interpreter's "thread switch interval"; see |
| 507 | :func:`setswitchinterval`. |
| 508 | |
Antoine Pitrou | 79707ca | 2009-11-11 22:03:32 +0000 | [diff] [blame] | 509 | .. versionadded:: 3.2 |
| 510 | |
Antoine Pitrou | d42bc51 | 2009-11-10 23:18:31 +0000 | [diff] [blame] | 511 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 512 | .. function:: _getframe([depth]) |
| 513 | |
| 514 | Return a frame object from the call stack. If optional integer *depth* is |
| 515 | given, return the frame object that many calls below the top of the stack. If |
| 516 | that is deeper than the call stack, :exc:`ValueError` is raised. The default |
| 517 | for *depth* is zero, returning the frame at the top of the call stack. |
| 518 | |
Georg Brandl | 495f7b5 | 2009-10-27 15:28:25 +0000 | [diff] [blame] | 519 | .. impl-detail:: |
| 520 | |
| 521 | This function should be used for internal and specialized purposes only. |
| 522 | It is not guaranteed to exist in all implementations of Python. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 523 | |
| 524 | |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 525 | .. function:: getprofile() |
| 526 | |
| 527 | .. index:: |
| 528 | single: profile function |
| 529 | single: profiler |
| 530 | |
| 531 | Get the profiler function as set by :func:`setprofile`. |
| 532 | |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 533 | |
| 534 | .. function:: gettrace() |
| 535 | |
| 536 | .. index:: |
| 537 | single: trace function |
| 538 | single: debugger |
| 539 | |
| 540 | Get the trace function as set by :func:`settrace`. |
| 541 | |
Georg Brandl | 495f7b5 | 2009-10-27 15:28:25 +0000 | [diff] [blame] | 542 | .. impl-detail:: |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 543 | |
| 544 | The :func:`gettrace` function is intended only for implementing debuggers, |
Georg Brandl | 495f7b5 | 2009-10-27 15:28:25 +0000 | [diff] [blame] | 545 | profilers, coverage tools and the like. Its behavior is part of the |
| 546 | implementation platform, rather than part of the language definition, and |
| 547 | thus may not be available in all Python implementations. |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 548 | |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 549 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 550 | .. function:: getwindowsversion() |
| 551 | |
Eric Smith | 7338a39 | 2010-01-27 00:56:30 +0000 | [diff] [blame] | 552 | Return a named tuple describing the Windows version |
Eric Smith | f7bb578 | 2010-01-27 00:44:57 +0000 | [diff] [blame] | 553 | currently running. The named elements are *major*, *minor*, |
| 554 | *build*, *platform*, *service_pack*, *service_pack_minor*, |
Steve Dower | 74f4af7 | 2016-09-17 17:27:48 -0700 | [diff] [blame] | 555 | *service_pack_major*, *suite_mask*, *product_type* and |
| 556 | *platform_version*. *service_pack* contains a string, |
| 557 | *platform_version* a 3-tuple and all other values are |
Eric Smith | f7bb578 | 2010-01-27 00:44:57 +0000 | [diff] [blame] | 558 | integers. The components can also be accessed by name, so |
| 559 | ``sys.getwindowsversion()[0]`` is equivalent to |
| 560 | ``sys.getwindowsversion().major``. For compatibility with prior |
| 561 | versions, only the first 5 elements are retrievable by indexing. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 562 | |
Steve Dower | 74f4af7 | 2016-09-17 17:27:48 -0700 | [diff] [blame] | 563 | *platform* will be :const:`2 (VER_PLATFORM_WIN32_NT)`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 564 | |
Eric Smith | f7bb578 | 2010-01-27 00:44:57 +0000 | [diff] [blame] | 565 | *product_type* may be one of the following values: |
| 566 | |
| 567 | +---------------------------------------+---------------------------------+ |
| 568 | | Constant | Meaning | |
| 569 | +=======================================+=================================+ |
| 570 | | :const:`1 (VER_NT_WORKSTATION)` | The system is a workstation. | |
| 571 | +---------------------------------------+---------------------------------+ |
| 572 | | :const:`2 (VER_NT_DOMAIN_CONTROLLER)` | The system is a domain | |
| 573 | | | controller. | |
| 574 | +---------------------------------------+---------------------------------+ |
| 575 | | :const:`3 (VER_NT_SERVER)` | The system is a server, but not | |
| 576 | | | a domain controller. | |
| 577 | +---------------------------------------+---------------------------------+ |
| 578 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 579 | This function wraps the Win32 :c:func:`GetVersionEx` function; see the |
| 580 | Microsoft documentation on :c:func:`OSVERSIONINFOEX` for more information |
Eric Smith | f7bb578 | 2010-01-27 00:44:57 +0000 | [diff] [blame] | 581 | about these fields. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 582 | |
Steve Dower | 74f4af7 | 2016-09-17 17:27:48 -0700 | [diff] [blame] | 583 | *platform_version* returns the accurate major version, minor version and |
| 584 | build number of the current operating system, rather than the version that |
| 585 | is being emulated for the process. It is intended for use in logging rather |
| 586 | than for feature detection. |
| 587 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 588 | Availability: Windows. |
| 589 | |
Ezio Melotti | 83fc6dd | 2010-01-27 22:44:03 +0000 | [diff] [blame] | 590 | .. versionchanged:: 3.2 |
Eric Smith | f7bb578 | 2010-01-27 00:44:57 +0000 | [diff] [blame] | 591 | Changed to a named tuple and added *service_pack_minor*, |
| 592 | *service_pack_major*, *suite_mask*, and *product_type*. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 593 | |
Steve Dower | 74f4af7 | 2016-09-17 17:27:48 -0700 | [diff] [blame] | 594 | .. versionchanged:: 3.6 |
| 595 | Added *platform_version* |
Mark Dickinson | dc787d2 | 2010-05-23 13:33:13 +0000 | [diff] [blame] | 596 | |
Yury Selivanov | 0366004 | 2016-12-15 17:36:05 -0500 | [diff] [blame^] | 597 | |
| 598 | .. function:: get_asyncgen_hooks() |
| 599 | |
| 600 | Returns an *asyncgen_hooks* object, which is similar to a |
| 601 | :class:`~collections.namedtuple` of the form `(firstiter, finalizer)`, |
| 602 | where *firstiter* and *finalizer* are expected to be either ``None`` or |
| 603 | functions which take an :term:`asynchronous generator iterator` as an |
| 604 | argument, and are used to schedule finalization of an asychronous |
| 605 | generator by an event loop. |
| 606 | |
| 607 | .. versionadded:: 3.6 |
| 608 | See :pep:`525` for more details. |
| 609 | |
| 610 | .. note:: |
| 611 | This function has been added on a provisional basis (see :pep:`411` |
| 612 | for details.) |
| 613 | |
| 614 | |
Yury Selivanov | d4cbbeb | 2015-05-31 17:13:08 -0400 | [diff] [blame] | 615 | .. function:: get_coroutine_wrapper() |
| 616 | |
| 617 | Returns ``None``, or a wrapper set by :func:`set_coroutine_wrapper`. |
| 618 | |
| 619 | .. versionadded:: 3.5 |
| 620 | See :pep:`492` for more details. |
| 621 | |
| 622 | .. note:: |
| 623 | This function has been added on a provisional basis (see :pep:`411` |
Yury Selivanov | 4180e43 | 2015-06-04 11:10:24 -0400 | [diff] [blame] | 624 | for details.) Use it only for debugging purposes. |
Yury Selivanov | d4cbbeb | 2015-05-31 17:13:08 -0400 | [diff] [blame] | 625 | |
| 626 | |
Mark Dickinson | dc787d2 | 2010-05-23 13:33:13 +0000 | [diff] [blame] | 627 | .. data:: hash_info |
| 628 | |
Benjamin Peterson | 2b8ef2d | 2011-04-20 18:31:22 -0500 | [diff] [blame] | 629 | A :term:`struct sequence` giving parameters of the numeric hash |
| 630 | implementation. For more details about hashing of numeric types, see |
| 631 | :ref:`numeric-hash`. |
Mark Dickinson | dc787d2 | 2010-05-23 13:33:13 +0000 | [diff] [blame] | 632 | |
| 633 | +---------------------+--------------------------------------------------+ |
| 634 | | attribute | explanation | |
| 635 | +=====================+==================================================+ |
| 636 | | :const:`width` | width in bits used for hash values | |
| 637 | +---------------------+--------------------------------------------------+ |
| 638 | | :const:`modulus` | prime modulus P used for numeric hash scheme | |
| 639 | +---------------------+--------------------------------------------------+ |
| 640 | | :const:`inf` | hash value returned for a positive infinity | |
| 641 | +---------------------+--------------------------------------------------+ |
| 642 | | :const:`nan` | hash value returned for a nan | |
| 643 | +---------------------+--------------------------------------------------+ |
| 644 | | :const:`imag` | multiplier used for the imaginary part of a | |
| 645 | | | complex number | |
| 646 | +---------------------+--------------------------------------------------+ |
Christian Heimes | 985ecdc | 2013-11-20 11:46:18 +0100 | [diff] [blame] | 647 | | :const:`algorithm` | name of the algorithm for hashing of str, bytes, | |
| 648 | | | and memoryview | |
| 649 | +---------------------+--------------------------------------------------+ |
| 650 | | :const:`hash_bits` | internal output size of the hash algorithm | |
| 651 | +---------------------+--------------------------------------------------+ |
| 652 | | :const:`seed_bits` | size of the seed key of the hash algorithm | |
| 653 | +---------------------+--------------------------------------------------+ |
| 654 | |
Mark Dickinson | dc787d2 | 2010-05-23 13:33:13 +0000 | [diff] [blame] | 655 | |
| 656 | .. versionadded:: 3.2 |
| 657 | |
R David Murray | f93d3df | 2014-03-17 11:20:29 -0400 | [diff] [blame] | 658 | .. versionchanged:: 3.4 |
Christian Heimes | 985ecdc | 2013-11-20 11:46:18 +0100 | [diff] [blame] | 659 | Added *algorithm*, *hash_bits* and *seed_bits* |
| 660 | |
Mark Dickinson | dc787d2 | 2010-05-23 13:33:13 +0000 | [diff] [blame] | 661 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 662 | .. data:: hexversion |
| 663 | |
| 664 | The version number encoded as a single integer. This is guaranteed to increase |
| 665 | with each version, including proper support for non-production releases. For |
| 666 | example, to test that the Python interpreter is at least version 1.5.2, use:: |
| 667 | |
| 668 | if sys.hexversion >= 0x010502F0: |
| 669 | # use some advanced feature |
| 670 | ... |
| 671 | else: |
| 672 | # use an alternative implementation or warn the user |
| 673 | ... |
| 674 | |
| 675 | This is called ``hexversion`` since it only really looks meaningful when viewed |
| 676 | 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] | 677 | :term:`struct sequence` :data:`sys.version_info` may be used for a more |
| 678 | human-friendly encoding of the same information. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 679 | |
Martin Panter | d21e0b5 | 2015-10-10 10:36:22 +0000 | [diff] [blame] | 680 | More details of ``hexversion`` can be found at :ref:`apiabiversion`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 681 | |
Barry Warsaw | 409da15 | 2012-06-03 16:18:47 -0400 | [diff] [blame] | 682 | |
| 683 | .. data:: implementation |
| 684 | |
Barry Warsaw | 9b10e1f | 2012-06-04 11:06:45 -0400 | [diff] [blame] | 685 | An object containing information about the implementation of the |
| 686 | currently running Python interpreter. The following attributes are |
| 687 | required to exist in all Python implementations. |
Barry Warsaw | 409da15 | 2012-06-03 16:18:47 -0400 | [diff] [blame] | 688 | |
Barry Warsaw | 9b10e1f | 2012-06-04 11:06:45 -0400 | [diff] [blame] | 689 | *name* is the implementation's identifier, e.g. ``'cpython'``. The actual |
| 690 | string is defined by the Python implementation, but it is guaranteed to be |
| 691 | lower case. |
Barry Warsaw | 409da15 | 2012-06-03 16:18:47 -0400 | [diff] [blame] | 692 | |
| 693 | *version* is a named tuple, in the same format as |
| 694 | :data:`sys.version_info`. It represents the version of the Python |
| 695 | *implementation*. This has a distinct meaning from the specific |
| 696 | version of the Python *language* to which the currently running |
| 697 | interpreter conforms, which ``sys.version_info`` represents. For |
| 698 | example, for PyPy 1.8 ``sys.implementation.version`` might be |
| 699 | ``sys.version_info(1, 8, 0, 'final', 0)``, whereas ``sys.version_info`` |
Barry Warsaw | 9b10e1f | 2012-06-04 11:06:45 -0400 | [diff] [blame] | 700 | 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] | 701 | are the same value, since it is the reference implementation. |
| 702 | |
| 703 | *hexversion* is the implementation version in hexadecimal format, like |
| 704 | :data:`sys.hexversion`. |
| 705 | |
| 706 | *cache_tag* is the tag used by the import machinery in the filenames of |
| 707 | cached modules. By convention, it would be a composite of the |
| 708 | implementation's name and version, like ``'cpython-33'``. However, a |
| 709 | Python implementation may use some other value if appropriate. If |
| 710 | ``cache_tag`` is set to ``None``, it indicates that module caching should |
| 711 | be disabled. |
| 712 | |
Barry Warsaw | 9b10e1f | 2012-06-04 11:06:45 -0400 | [diff] [blame] | 713 | :data:`sys.implementation` may contain additional attributes specific to |
| 714 | the Python implementation. These non-standard attributes must start with |
| 715 | an underscore, and are not described here. Regardless of its contents, |
| 716 | :data:`sys.implementation` will not change during a run of the interpreter, |
| 717 | nor between implementation versions. (It may change between Python |
Georg Brandl | 93a56cd | 2014-10-30 22:25:41 +0100 | [diff] [blame] | 718 | language versions, however.) See :pep:`421` for more information. |
Barry Warsaw | 409da15 | 2012-06-03 16:18:47 -0400 | [diff] [blame] | 719 | |
| 720 | .. versionadded:: 3.3 |
| 721 | |
| 722 | |
Mark Dickinson | bd79264 | 2009-03-18 20:06:12 +0000 | [diff] [blame] | 723 | .. data:: int_info |
| 724 | |
Benjamin Peterson | 2b8ef2d | 2011-04-20 18:31:22 -0500 | [diff] [blame] | 725 | A :term:`struct sequence` that holds information about Python's internal |
| 726 | representation of integers. The attributes are read only. |
Mark Dickinson | bd79264 | 2009-03-18 20:06:12 +0000 | [diff] [blame] | 727 | |
Georg Brandl | 44ea77b | 2013-03-28 13:28:44 +0100 | [diff] [blame] | 728 | .. tabularcolumns:: |l|L| |
| 729 | |
Mark Dickinson | bd79264 | 2009-03-18 20:06:12 +0000 | [diff] [blame] | 730 | +-------------------------+----------------------------------------------+ |
R David Murray | 9beb34e | 2011-04-30 16:35:29 -0400 | [diff] [blame] | 731 | | Attribute | Explanation | |
Mark Dickinson | bd79264 | 2009-03-18 20:06:12 +0000 | [diff] [blame] | 732 | +=========================+==============================================+ |
| 733 | | :const:`bits_per_digit` | number of bits held in each digit. Python | |
| 734 | | | integers are stored internally in base | |
| 735 | | | ``2**int_info.bits_per_digit`` | |
| 736 | +-------------------------+----------------------------------------------+ |
| 737 | | :const:`sizeof_digit` | size in bytes of the C type used to | |
| 738 | | | represent a digit | |
| 739 | +-------------------------+----------------------------------------------+ |
| 740 | |
Mark Dickinson | d72c7b6 | 2009-03-20 16:00:49 +0000 | [diff] [blame] | 741 | .. versionadded:: 3.1 |
| 742 | |
Mark Dickinson | bd79264 | 2009-03-18 20:06:12 +0000 | [diff] [blame] | 743 | |
Antoine Pitrou | 1a6cb30 | 2013-05-04 20:08:35 +0200 | [diff] [blame] | 744 | .. data:: __interactivehook__ |
| 745 | |
Larry Hastings | 3732ed2 | 2014-03-15 21:13:56 -0700 | [diff] [blame] | 746 | When this attribute exists, its value is automatically called (with no |
| 747 | arguments) when the interpreter is launched in :ref:`interactive mode |
| 748 | <tut-interactive>`. This is done after the :envvar:`PYTHONSTARTUP` file is |
| 749 | read, so that you can set this hook there. The :mod:`site` module |
| 750 | :ref:`sets this <rlcompleter-config>`. |
Antoine Pitrou | 1a6cb30 | 2013-05-04 20:08:35 +0200 | [diff] [blame] | 751 | |
| 752 | .. versionadded:: 3.4 |
| 753 | |
| 754 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 755 | .. function:: intern(string) |
| 756 | |
| 757 | Enter *string* in the table of "interned" strings and return the interned string |
| 758 | -- which is *string* itself or a copy. Interning strings is useful to gain a |
| 759 | little performance on dictionary lookup -- if the keys in a dictionary are |
| 760 | interned, and the lookup key is interned, the key comparisons (after hashing) |
| 761 | can be done by a pointer compare instead of a string compare. Normally, the |
| 762 | names used in Python programs are automatically interned, and the dictionaries |
| 763 | used to hold module, class or instance attributes have interned keys. |
| 764 | |
Georg Brandl | 55ac8f0 | 2007-09-01 13:51:09 +0000 | [diff] [blame] | 765 | Interned strings are not immortal; you must keep a reference to the return |
| 766 | value of :func:`intern` around to benefit from it. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 767 | |
| 768 | |
Antoine Pitrou | 5db1bb8 | 2014-12-07 01:28:27 +0100 | [diff] [blame] | 769 | .. function:: is_finalizing() |
| 770 | |
| 771 | Return :const:`True` if the Python interpreter is |
| 772 | :term:`shutting down <interpreter shutdown>`, :const:`False` otherwise. |
| 773 | |
| 774 | .. versionadded:: 3.5 |
| 775 | |
| 776 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 777 | .. data:: last_type |
| 778 | last_value |
| 779 | last_traceback |
| 780 | |
| 781 | These three variables are not always defined; they are set when an exception is |
| 782 | not handled and the interpreter prints an error message and a stack traceback. |
| 783 | Their intended use is to allow an interactive user to import a debugger module |
| 784 | and engage in post-mortem debugging without having to re-execute the command |
| 785 | 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] | 786 | post-mortem debugger; see :mod:`pdb` module for |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 787 | more information.) |
| 788 | |
| 789 | 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] | 790 | :func:`exc_info` above. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 791 | |
| 792 | |
Christian Heimes | a37d4c6 | 2007-12-04 23:02:19 +0000 | [diff] [blame] | 793 | .. data:: maxsize |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 794 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 795 | 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] | 796 | take. It's usually ``2**31 - 1`` on a 32-bit platform and ``2**63 - 1`` on a |
| 797 | 64-bit platform. |
Christian Heimes | a37d4c6 | 2007-12-04 23:02:19 +0000 | [diff] [blame] | 798 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 799 | |
| 800 | .. data:: maxunicode |
| 801 | |
Ezio Melotti | 48a2f8f | 2011-09-29 00:18:19 +0300 | [diff] [blame] | 802 | An integer giving the value of the largest Unicode code point, |
| 803 | i.e. ``1114111`` (``0x10FFFF`` in hexadecimal). |
| 804 | |
| 805 | .. versionchanged:: 3.3 |
Éric Araujo | 525b1e9 | 2011-10-05 01:06:31 +0200 | [diff] [blame] | 806 | Before :pep:`393`, ``sys.maxunicode`` used to be either ``0xFFFF`` |
Ezio Melotti | 48a2f8f | 2011-09-29 00:18:19 +0300 | [diff] [blame] | 807 | or ``0x10FFFF``, depending on the configuration option that specified |
| 808 | whether Unicode characters were stored as UCS-2 or UCS-4. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 809 | |
| 810 | |
Brett Cannon | e43b060 | 2009-03-21 03:11:16 +0000 | [diff] [blame] | 811 | .. data:: meta_path |
| 812 | |
Brett Cannon | ccddbb1 | 2015-12-04 15:46:21 -0800 | [diff] [blame] | 813 | A list of :term:`meta path finder` objects that have their |
| 814 | :meth:`~importlib.abc.MetaPathFinder.find_spec` methods called to see if one |
| 815 | of the objects can find the module to be imported. The |
| 816 | :meth:`~importlib.abc.MetaPathFinder.find_spec` method is called with at |
| 817 | least the absolute name of the module being imported. If the module to be |
| 818 | imported is contained in a package, then the parent package's :attr:`__path__` |
| 819 | attribute is passed in as a second argument. The method returns a |
| 820 | :term:`module spec`, or ``None`` if the module cannot be found. |
Brett Cannon | e43b060 | 2009-03-21 03:11:16 +0000 | [diff] [blame] | 821 | |
Brett Cannon | ccddbb1 | 2015-12-04 15:46:21 -0800 | [diff] [blame] | 822 | .. seealso:: |
Brett Cannon | e43b060 | 2009-03-21 03:11:16 +0000 | [diff] [blame] | 823 | |
Brett Cannon | ccddbb1 | 2015-12-04 15:46:21 -0800 | [diff] [blame] | 824 | :class:`importlib.abc.MetaPathFinder` |
| 825 | The abstract base class defining the interface of finder objects on |
| 826 | :data:`meta_path`. |
| 827 | :class:`importlib.machinery.ModuleSpec` |
| 828 | The concrete class which |
| 829 | :meth:`~importlib.abc.MetaPathFinder.find_spec` should return |
| 830 | instances of. |
Brett Cannon | e43b060 | 2009-03-21 03:11:16 +0000 | [diff] [blame] | 831 | |
Brett Cannon | ccddbb1 | 2015-12-04 15:46:21 -0800 | [diff] [blame] | 832 | .. versionchanged:: 3.4 |
| 833 | |
| 834 | :term:`Module specs <module spec>` were introduced in Python 3.4, by |
| 835 | :pep:`451`. Earlier versions of Python looked for a method called |
| 836 | :meth:`~importlib.abc.MetaPathFinder.find_module`. |
| 837 | This is still called as a fallback if a :data:`meta_path` entry doesn't |
| 838 | have a :meth:`~importlib.abc.MetaPathFinder.find_spec` method. |
Brett Cannon | e43b060 | 2009-03-21 03:11:16 +0000 | [diff] [blame] | 839 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 840 | .. data:: modules |
| 841 | |
| 842 | This is a dictionary that maps module names to modules which have already been |
| 843 | 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] | 844 | However, replacing the dictionary will not necessarily work as expected and |
| 845 | deleting essential items from the dictionary may cause Python to fail. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 846 | |
| 847 | |
| 848 | .. data:: path |
| 849 | |
| 850 | .. index:: triple: module; search; path |
| 851 | |
| 852 | A list of strings that specifies the search path for modules. Initialized from |
| 853 | the environment variable :envvar:`PYTHONPATH`, plus an installation-dependent |
| 854 | default. |
| 855 | |
| 856 | As initialized upon program startup, the first item of this list, ``path[0]``, |
| 857 | is the directory containing the script that was used to invoke the Python |
| 858 | interpreter. If the script directory is not available (e.g. if the interpreter |
| 859 | is invoked interactively or if the script is read from standard input), |
| 860 | ``path[0]`` is the empty string, which directs Python to search modules in the |
| 861 | current directory first. Notice that the script directory is inserted *before* |
| 862 | the entries inserted as a result of :envvar:`PYTHONPATH`. |
| 863 | |
Barry Warsaw | 82c1c78 | 2012-11-20 15:22:51 -0500 | [diff] [blame] | 864 | A program is free to modify this list for its own purposes. Only strings |
| 865 | and bytes should be added to :data:`sys.path`; all other data types are |
| 866 | ignored during import. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 867 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 868 | |
Benjamin Peterson | 058e31e | 2009-01-16 03:54:08 +0000 | [diff] [blame] | 869 | .. seealso:: |
| 870 | Module :mod:`site` This describes how to use .pth files to extend |
| 871 | :data:`sys.path`. |
| 872 | |
| 873 | |
Brett Cannon | e43b060 | 2009-03-21 03:11:16 +0000 | [diff] [blame] | 874 | .. data:: path_hooks |
| 875 | |
| 876 | A list of callables that take a path argument to try to create a |
| 877 | :term:`finder` for the path. If a finder can be created, it is to be |
| 878 | returned by the callable, else raise :exc:`ImportError`. |
| 879 | |
| 880 | Originally specified in :pep:`302`. |
| 881 | |
| 882 | |
| 883 | .. data:: path_importer_cache |
| 884 | |
| 885 | A dictionary acting as a cache for :term:`finder` objects. The keys are |
| 886 | paths that have been passed to :data:`sys.path_hooks` and the values are |
| 887 | 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] | 888 | finder is found on :data:`sys.path_hooks` then ``None`` is |
| 889 | stored. |
Brett Cannon | e43b060 | 2009-03-21 03:11:16 +0000 | [diff] [blame] | 890 | |
| 891 | Originally specified in :pep:`302`. |
| 892 | |
Brett Cannon | 2514b48 | 2013-03-13 10:46:22 -0700 | [diff] [blame] | 893 | .. versionchanged:: 3.3 |
| 894 | ``None`` is stored instead of :class:`imp.NullImporter` when no finder |
| 895 | is found. |
| 896 | |
Brett Cannon | e43b060 | 2009-03-21 03:11:16 +0000 | [diff] [blame] | 897 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 898 | .. data:: platform |
| 899 | |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 900 | This string contains a platform identifier that can be used to append |
| 901 | platform-specific components to :data:`sys.path`, for instance. |
| 902 | |
Victor Stinner | 795eaeb | 2011-08-21 12:08:11 +0200 | [diff] [blame] | 903 | For Unix systems, except on Linux, this is the lowercased OS name as |
| 904 | returned by ``uname -s`` with the first part of the version as returned by |
| 905 | ``uname -r`` appended, e.g. ``'sunos5'`` or ``'freebsd8'``, *at the time |
| 906 | when Python was built*. Unless you want to test for a specific system |
| 907 | version, it is therefore recommended to use the following idiom:: |
Antoine Pitrou | a83cdaa | 2011-07-09 15:54:23 +0200 | [diff] [blame] | 908 | |
Victor Stinner | 795eaeb | 2011-08-21 12:08:11 +0200 | [diff] [blame] | 909 | if sys.platform.startswith('freebsd'): |
| 910 | # FreeBSD-specific code here... |
Georg Brandl | a47e53e | 2011-09-03 09:26:09 +0200 | [diff] [blame] | 911 | elif sys.platform.startswith('linux'): |
Antoine Pitrou | a83cdaa | 2011-07-09 15:54:23 +0200 | [diff] [blame] | 912 | # Linux-specific code here... |
| 913 | |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 914 | For other systems, the values are: |
| 915 | |
| 916 | ================ =========================== |
Éric Araujo | 3f7c0e4 | 2012-12-08 22:53:43 -0500 | [diff] [blame] | 917 | System ``platform`` value |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 918 | ================ =========================== |
Victor Stinner | 795eaeb | 2011-08-21 12:08:11 +0200 | [diff] [blame] | 919 | Linux ``'linux'`` |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 920 | Windows ``'win32'`` |
| 921 | Windows/Cygwin ``'cygwin'`` |
Georg Brandl | c575c90 | 2008-09-13 17:46:05 +0000 | [diff] [blame] | 922 | Mac OS X ``'darwin'`` |
Christian Heimes | 9bd667a | 2008-01-20 15:14:11 +0000 | [diff] [blame] | 923 | ================ =========================== |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 924 | |
Victor Stinner | 795eaeb | 2011-08-21 12:08:11 +0200 | [diff] [blame] | 925 | .. versionchanged:: 3.3 |
| 926 | On Linux, :attr:`sys.platform` doesn't contain the major version anymore. |
Georg Brandl | fbd1e04 | 2011-09-04 08:42:26 +0200 | [diff] [blame] | 927 | It is always ``'linux'``, instead of ``'linux2'`` or ``'linux3'``. Since |
| 928 | older Python versions include the version number, it is recommended to |
| 929 | always use the ``startswith`` idiom presented above. |
Victor Stinner | 795eaeb | 2011-08-21 12:08:11 +0200 | [diff] [blame] | 930 | |
Antoine Pitrou | a83cdaa | 2011-07-09 15:54:23 +0200 | [diff] [blame] | 931 | .. seealso:: |
Georg Brandl | eb25fb7 | 2012-02-23 21:12:39 +0100 | [diff] [blame] | 932 | |
Antoine Pitrou | a83cdaa | 2011-07-09 15:54:23 +0200 | [diff] [blame] | 933 | :attr:`os.name` has a coarser granularity. :func:`os.uname` gives |
| 934 | system-dependent version information. |
| 935 | |
| 936 | The :mod:`platform` module provides detailed checks for the |
| 937 | system's identity. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 938 | |
Georg Brandl | fbd1e04 | 2011-09-04 08:42:26 +0200 | [diff] [blame] | 939 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 940 | .. data:: prefix |
| 941 | |
| 942 | A string giving the site-specific directory prefix where the platform |
| 943 | independent Python files are installed; by default, this is the string |
Éric Araujo | 713d303 | 2010-11-18 16:38:46 +0000 | [diff] [blame] | 944 | ``'/usr/local'``. This can be set at build time with the ``--prefix`` |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 945 | argument to the :program:`configure` script. The main collection of Python |
Georg Brandl | a673eb8 | 2012-03-04 16:17:05 +0100 | [diff] [blame] | 946 | 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] | 947 | while the platform independent header files (all except :file:`pyconfig.h`) are |
Georg Brandl | eb25fb7 | 2012-02-23 21:12:39 +0100 | [diff] [blame] | 948 | 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] | 949 | number of Python, for example ``3.2``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 950 | |
Vinay Sajip | cd9b746 | 2012-07-09 10:37:01 +0100 | [diff] [blame] | 951 | .. note:: If a :ref:`virtual environment <venv-def>` is in effect, this |
| 952 | value will be changed in ``site.py`` to point to the virtual |
| 953 | environment. The value for the Python installation will still be |
| 954 | available, via :data:`base_prefix`. |
Vinay Sajip | 7ded1f0 | 2012-05-26 03:45:29 +0100 | [diff] [blame] | 955 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 956 | |
| 957 | .. data:: ps1 |
| 958 | ps2 |
| 959 | |
| 960 | .. index:: |
| 961 | single: interpreter prompts |
| 962 | single: prompts, interpreter |
| 963 | |
| 964 | Strings specifying the primary and secondary prompt of the interpreter. These |
| 965 | are only defined if the interpreter is in interactive mode. Their initial |
| 966 | values in this case are ``'>>> '`` and ``'... '``. If a non-string object is |
| 967 | assigned to either variable, its :func:`str` is re-evaluated each time the |
| 968 | interpreter prepares to read a new interactive command; this can be used to |
| 969 | implement a dynamic prompt. |
| 970 | |
| 971 | |
| 972 | .. function:: setcheckinterval(interval) |
| 973 | |
| 974 | Set the interpreter's "check interval". This integer value determines how often |
| 975 | the interpreter checks for periodic things such as thread switches and signal |
| 976 | handlers. The default is ``100``, meaning the check is performed every 100 |
| 977 | Python virtual instructions. Setting it to a larger value may increase |
| 978 | performance for programs using threads. Setting it to a value ``<=`` 0 checks |
| 979 | every virtual instruction, maximizing responsiveness as well as overhead. |
| 980 | |
Antoine Pitrou | d42bc51 | 2009-11-10 23:18:31 +0000 | [diff] [blame] | 981 | .. deprecated:: 3.2 |
Georg Brandl | 67b21b7 | 2010-08-17 15:07:14 +0000 | [diff] [blame] | 982 | This function doesn't have an effect anymore, as the internal logic for |
| 983 | thread switching and asynchronous tasks has been rewritten. Use |
| 984 | :func:`setswitchinterval` instead. |
Antoine Pitrou | d42bc51 | 2009-11-10 23:18:31 +0000 | [diff] [blame] | 985 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 986 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 987 | .. function:: setdlopenflags(n) |
| 988 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 989 | 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] | 990 | the interpreter loads extension modules. Among other things, this will enable a |
| 991 | lazy resolving of symbols when importing a module, if called as |
| 992 | ``sys.setdlopenflags(0)``. To share symbols across extension modules, call as |
Andrew Kuchling | c61b913 | 2013-06-21 10:58:41 -0400 | [diff] [blame] | 993 | ``sys.setdlopenflags(os.RTLD_GLOBAL)``. Symbolic names for the flag values |
Victor Stinner | 8b905bd | 2011-10-25 13:34:04 +0200 | [diff] [blame] | 994 | can be found in the :mod:`os` module (``RTLD_xxx`` constants, e.g. |
| 995 | :data:`os.RTLD_LAZY`). |
| 996 | |
| 997 | Availability: Unix. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 998 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 999 | .. function:: setprofile(profilefunc) |
| 1000 | |
| 1001 | .. index:: |
| 1002 | single: profile function |
| 1003 | single: profiler |
| 1004 | |
| 1005 | Set the system's profile function, which allows you to implement a Python source |
| 1006 | code profiler in Python. See chapter :ref:`profile` for more information on the |
| 1007 | Python profiler. The system's profile function is called similarly to the |
| 1008 | system's trace function (see :func:`settrace`), but it isn't called for each |
| 1009 | executed line of code (only on call and return, but the return event is reported |
| 1010 | even when an exception has been set). The function is thread-specific, but |
| 1011 | there is no way for the profiler to know about context switches between threads, |
| 1012 | so it does not make sense to use this in the presence of multiple threads. Also, |
| 1013 | its return value is not used, so it can simply return ``None``. |
| 1014 | |
| 1015 | |
| 1016 | .. function:: setrecursionlimit(limit) |
| 1017 | |
| 1018 | Set the maximum depth of the Python interpreter stack to *limit*. This limit |
| 1019 | prevents infinite recursion from causing an overflow of the C stack and crashing |
| 1020 | Python. |
| 1021 | |
| 1022 | 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] | 1023 | 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] | 1024 | that supports a higher limit. This should be done with care, because a too-high |
| 1025 | limit can lead to a crash. |
| 1026 | |
Victor Stinner | 50856d5 | 2015-10-13 00:11:21 +0200 | [diff] [blame] | 1027 | If the new limit is too low at the current recursion depth, a |
| 1028 | :exc:`RecursionError` exception is raised. |
| 1029 | |
| 1030 | .. versionchanged:: 3.5.1 |
| 1031 | A :exc:`RecursionError` exception is now raised if the new limit is too |
| 1032 | low at the current recursion depth. |
| 1033 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1034 | |
Antoine Pitrou | d42bc51 | 2009-11-10 23:18:31 +0000 | [diff] [blame] | 1035 | .. function:: setswitchinterval(interval) |
| 1036 | |
| 1037 | Set the interpreter's thread switch interval (in seconds). This floating-point |
| 1038 | value determines the ideal duration of the "timeslices" allocated to |
| 1039 | concurrently running Python threads. Please note that the actual value |
| 1040 | can be higher, especially if long-running internal functions or methods |
| 1041 | are used. Also, which thread becomes scheduled at the end of the interval |
| 1042 | is the operating system's decision. The interpreter doesn't have its |
| 1043 | own scheduler. |
| 1044 | |
Antoine Pitrou | 79707ca | 2009-11-11 22:03:32 +0000 | [diff] [blame] | 1045 | .. versionadded:: 3.2 |
| 1046 | |
Antoine Pitrou | d42bc51 | 2009-11-10 23:18:31 +0000 | [diff] [blame] | 1047 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1048 | .. function:: settrace(tracefunc) |
| 1049 | |
| 1050 | .. index:: |
| 1051 | single: trace function |
| 1052 | single: debugger |
| 1053 | |
| 1054 | 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] | 1055 | source code debugger in Python. The function is thread-specific; for a |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1056 | debugger to support multiple threads, it must be registered using |
| 1057 | :func:`settrace` for each thread being debugged. |
| 1058 | |
Amaury Forgeot d'Arc | b0c2916 | 2008-11-22 22:18:04 +0000 | [diff] [blame] | 1059 | Trace functions should have three arguments: *frame*, *event*, and |
| 1060 | *arg*. *frame* is the current stack frame. *event* is a string: ``'call'``, |
| 1061 | ``'line'``, ``'return'``, ``'exception'``, ``'c_call'``, ``'c_return'``, or |
| 1062 | ``'c_exception'``. *arg* depends on the event type. |
| 1063 | |
| 1064 | The trace function is invoked (with *event* set to ``'call'``) whenever a new |
| 1065 | local scope is entered; it should return a reference to a local trace |
| 1066 | function to be used that scope, or ``None`` if the scope shouldn't be traced. |
| 1067 | |
| 1068 | The local trace function should return a reference to itself (or to another |
| 1069 | function for further tracing in that scope), or ``None`` to turn off tracing |
| 1070 | in that scope. |
| 1071 | |
| 1072 | The events have the following meaning: |
| 1073 | |
Georg Brandl | 48310cd | 2009-01-03 21:18:54 +0000 | [diff] [blame] | 1074 | ``'call'`` |
Amaury Forgeot d'Arc | b0c2916 | 2008-11-22 22:18:04 +0000 | [diff] [blame] | 1075 | A function is called (or some other code block entered). The |
| 1076 | global trace function is called; *arg* is ``None``; the return value |
| 1077 | specifies the local trace function. |
| 1078 | |
| 1079 | ``'line'`` |
Alexandre Vassalotti | 7b82b40 | 2009-07-21 04:30:03 +0000 | [diff] [blame] | 1080 | The interpreter is about to execute a new line of code or re-execute the |
| 1081 | condition of a loop. The local trace function is called; *arg* is |
| 1082 | ``None``; the return value specifies the new local trace function. See |
| 1083 | :file:`Objects/lnotab_notes.txt` for a detailed explanation of how this |
| 1084 | works. |
Amaury Forgeot d'Arc | b0c2916 | 2008-11-22 22:18:04 +0000 | [diff] [blame] | 1085 | |
| 1086 | ``'return'`` |
| 1087 | 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] | 1088 | function is called; *arg* is the value that will be returned, or ``None`` |
| 1089 | if the event is caused by an exception being raised. The trace function's |
| 1090 | return value is ignored. |
Amaury Forgeot d'Arc | b0c2916 | 2008-11-22 22:18:04 +0000 | [diff] [blame] | 1091 | |
| 1092 | ``'exception'`` |
| 1093 | An exception has occurred. The local trace function is called; *arg* is a |
| 1094 | tuple ``(exception, value, traceback)``; the return value specifies the |
| 1095 | new local trace function. |
| 1096 | |
| 1097 | ``'c_call'`` |
| 1098 | A C function is about to be called. This may be an extension function or |
Georg Brandl | 22b3431 | 2009-07-26 14:54:51 +0000 | [diff] [blame] | 1099 | a built-in. *arg* is the C function object. |
Amaury Forgeot d'Arc | b0c2916 | 2008-11-22 22:18:04 +0000 | [diff] [blame] | 1100 | |
| 1101 | ``'c_return'`` |
Georg Brandl | d0b0e1d | 2010-10-15 16:42:37 +0000 | [diff] [blame] | 1102 | A C function has returned. *arg* is the C function object. |
Amaury Forgeot d'Arc | b0c2916 | 2008-11-22 22:18:04 +0000 | [diff] [blame] | 1103 | |
| 1104 | ``'c_exception'`` |
Georg Brandl | d0b0e1d | 2010-10-15 16:42:37 +0000 | [diff] [blame] | 1105 | A C function has raised an exception. *arg* is the C function object. |
Amaury Forgeot d'Arc | b0c2916 | 2008-11-22 22:18:04 +0000 | [diff] [blame] | 1106 | |
| 1107 | Note that as an exception is propagated down the chain of callers, an |
| 1108 | ``'exception'`` event is generated at each level. |
| 1109 | |
| 1110 | For more information on code and frame objects, refer to :ref:`types`. |
| 1111 | |
Georg Brandl | 495f7b5 | 2009-10-27 15:28:25 +0000 | [diff] [blame] | 1112 | .. impl-detail:: |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1113 | |
| 1114 | The :func:`settrace` function is intended only for implementing debuggers, |
Georg Brandl | 495f7b5 | 2009-10-27 15:28:25 +0000 | [diff] [blame] | 1115 | profilers, coverage tools and the like. Its behavior is part of the |
| 1116 | implementation platform, rather than part of the language definition, and |
| 1117 | thus may not be available in all Python implementations. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1118 | |
Yury Selivanov | 0366004 | 2016-12-15 17:36:05 -0500 | [diff] [blame^] | 1119 | .. function:: set_asyncgen_hooks(firstiter, finalizer) |
| 1120 | |
| 1121 | Accepts two optional keyword arguments which are callables that accept an |
| 1122 | :term:`asynchronous generator iterator` as an argument. The *firstiter* |
| 1123 | callable will be called when an asynchronous generator is iterated for the |
| 1124 | first time. The *finalizer* will be called when an asynchronous generator |
| 1125 | is about to be garbage collected. |
| 1126 | |
| 1127 | .. versionadded:: 3.6 |
| 1128 | See :pep:`525` for more details, and for a reference example of a |
| 1129 | *finalizer* method see the implementation of |
| 1130 | ``asyncio.Loop.shutdown_asyncgens`` in |
| 1131 | :source:`Lib/asyncio/base_events.py` |
| 1132 | |
| 1133 | .. note:: |
| 1134 | This function has been added on a provisional basis (see :pep:`411` |
| 1135 | for details.) |
| 1136 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1137 | |
Yury Selivanov | d4cbbeb | 2015-05-31 17:13:08 -0400 | [diff] [blame] | 1138 | .. function:: set_coroutine_wrapper(wrapper) |
| 1139 | |
Yury Selivanov | 5376ba9 | 2015-06-22 12:19:30 -0400 | [diff] [blame] | 1140 | Allows intercepting creation of :term:`coroutine` objects (only ones that |
| 1141 | are created by an :keyword:`async def` function; generators decorated with |
| 1142 | :func:`types.coroutine` or :func:`asyncio.coroutine` will not be |
| 1143 | intercepted). |
Yury Selivanov | d4cbbeb | 2015-05-31 17:13:08 -0400 | [diff] [blame] | 1144 | |
Yury Selivanov | 66f8828 | 2015-06-24 11:04:15 -0400 | [diff] [blame] | 1145 | The *wrapper* argument must be either: |
Yury Selivanov | d4cbbeb | 2015-05-31 17:13:08 -0400 | [diff] [blame] | 1146 | |
| 1147 | * a callable that accepts one argument (a coroutine object); |
| 1148 | * ``None``, to reset the wrapper. |
| 1149 | |
| 1150 | If called twice, the new wrapper replaces the previous one. The function |
| 1151 | is thread-specific. |
| 1152 | |
Yury Selivanov | aab3c4a | 2015-06-02 18:43:51 -0400 | [diff] [blame] | 1153 | The *wrapper* callable cannot define new coroutines directly or indirectly:: |
| 1154 | |
| 1155 | def wrapper(coro): |
| 1156 | async def wrap(coro): |
| 1157 | return await coro |
| 1158 | return wrap(coro) |
| 1159 | sys.set_coroutine_wrapper(wrapper) |
| 1160 | |
Yury Selivanov | 66f8828 | 2015-06-24 11:04:15 -0400 | [diff] [blame] | 1161 | async def foo(): |
| 1162 | pass |
Yury Selivanov | aab3c4a | 2015-06-02 18:43:51 -0400 | [diff] [blame] | 1163 | |
| 1164 | # The following line will fail with a RuntimeError, because |
Zachary Ware | 3d3aedc | 2015-07-07 00:07:25 -0500 | [diff] [blame] | 1165 | # ``wrapper`` creates a ``wrap(coro)`` coroutine: |
Yury Selivanov | aab3c4a | 2015-06-02 18:43:51 -0400 | [diff] [blame] | 1166 | foo() |
| 1167 | |
Yury Selivanov | d4cbbeb | 2015-05-31 17:13:08 -0400 | [diff] [blame] | 1168 | See also :func:`get_coroutine_wrapper`. |
| 1169 | |
| 1170 | .. versionadded:: 3.5 |
| 1171 | See :pep:`492` for more details. |
| 1172 | |
| 1173 | .. note:: |
| 1174 | This function has been added on a provisional basis (see :pep:`411` |
Yury Selivanov | 4180e43 | 2015-06-04 11:10:24 -0400 | [diff] [blame] | 1175 | for details.) Use it only for debugging purposes. |
Yury Selivanov | d4cbbeb | 2015-05-31 17:13:08 -0400 | [diff] [blame] | 1176 | |
Steve Dower | cc16be8 | 2016-09-08 10:35:16 -0700 | [diff] [blame] | 1177 | .. function:: _enablelegacywindowsfsencoding() |
| 1178 | |
| 1179 | Changes the default filesystem encoding and errors mode to 'mbcs' and |
| 1180 | 'replace' respectively, for consistency with versions of Python prior to 3.6. |
| 1181 | |
| 1182 | This is equivalent to defining the :envvar:`PYTHONLEGACYWINDOWSFSENCODING` |
| 1183 | environment variable before launching Python. |
| 1184 | |
| 1185 | Availability: Windows |
| 1186 | |
| 1187 | .. versionadded:: 3.6 |
| 1188 | See :pep:`529` for more details. |
Yury Selivanov | d4cbbeb | 2015-05-31 17:13:08 -0400 | [diff] [blame] | 1189 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1190 | .. data:: stdin |
| 1191 | stdout |
| 1192 | stderr |
| 1193 | |
Antoine Pitrou | 7158e06 | 2011-12-15 16:25:34 +0100 | [diff] [blame] | 1194 | :term:`File objects <file object>` used by the interpreter for standard |
| 1195 | input, output and errors: |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1196 | |
Antoine Pitrou | 7158e06 | 2011-12-15 16:25:34 +0100 | [diff] [blame] | 1197 | * ``stdin`` is used for all interactive input (including calls to |
| 1198 | :func:`input`); |
| 1199 | * ``stdout`` is used for the output of :func:`print` and :term:`expression` |
| 1200 | statements and for the prompts of :func:`input`; |
| 1201 | * The interpreter's own prompts and its error messages go to ``stderr``. |
| 1202 | |
Antoine Pitrou | 2d1ec06 | 2014-05-15 22:38:56 +0200 | [diff] [blame] | 1203 | These streams are regular :term:`text files <text file>` like those |
| 1204 | returned by the :func:`open` function. Their parameters are chosen as |
| 1205 | follows: |
Antoine Pitrou | 7158e06 | 2011-12-15 16:25:34 +0100 | [diff] [blame] | 1206 | |
| 1207 | * The character encoding is platform-dependent. Under Windows, if the stream |
Serhiy Storchaka | fbc1c26 | 2013-11-29 12:17:13 +0200 | [diff] [blame] | 1208 | is interactive (that is, if its :meth:`isatty` method returns ``True``), the |
Antoine Pitrou | 7158e06 | 2011-12-15 16:25:34 +0100 | [diff] [blame] | 1209 | console codepage is used, otherwise the ANSI code page. Under other |
| 1210 | platforms, the locale encoding is used (see :meth:`locale.getpreferredencoding`). |
| 1211 | |
| 1212 | Under all platforms though, you can override this value by setting the |
Antoine Pitrou | 2d1ec06 | 2014-05-15 22:38:56 +0200 | [diff] [blame] | 1213 | :envvar:`PYTHONIOENCODING` environment variable before starting Python. |
Antoine Pitrou | 7158e06 | 2011-12-15 16:25:34 +0100 | [diff] [blame] | 1214 | |
| 1215 | * When interactive, standard streams are line-buffered. Otherwise, they |
| 1216 | are block-buffered like regular text files. You can override this |
| 1217 | value with the :option:`-u` command-line option. |
| 1218 | |
Antoine Pitrou | 2d1ec06 | 2014-05-15 22:38:56 +0200 | [diff] [blame] | 1219 | .. note:: |
Benjamin Peterson | 4199d60 | 2009-05-12 20:47:57 +0000 | [diff] [blame] | 1220 | |
Antoine Pitrou | 2d1ec06 | 2014-05-15 22:38:56 +0200 | [diff] [blame] | 1221 | To write or read binary data from/to the standard streams, use the |
| 1222 | underlying binary :data:`~io.TextIOBase.buffer` object. For example, to |
| 1223 | write bytes to :data:`stdout`, use ``sys.stdout.buffer.write(b'abc')``. |
Benjamin Peterson | 995bb47 | 2009-06-14 18:41:18 +0000 | [diff] [blame] | 1224 | |
Antoine Pitrou | 2d1ec06 | 2014-05-15 22:38:56 +0200 | [diff] [blame] | 1225 | However, if you are writing a library (and do not control in which |
| 1226 | context its code will be executed), be aware that the standard streams |
| 1227 | may be replaced with file-like objects like :class:`io.StringIO` which |
| 1228 | do not support the :attr:`~io.BufferedIOBase.buffer` attribute. |
Benjamin Peterson | eb9fc52 | 2008-12-07 14:58:03 +0000 | [diff] [blame] | 1229 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1230 | |
| 1231 | .. data:: __stdin__ |
| 1232 | __stdout__ |
| 1233 | __stderr__ |
| 1234 | |
| 1235 | These objects contain the original values of ``stdin``, ``stderr`` and |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 1236 | ``stdout`` at the start of the program. They are used during finalization, |
| 1237 | and could be useful to print to the actual standard stream no matter if the |
| 1238 | ``sys.std*`` object has been redirected. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1239 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 1240 | It can also be used to restore the actual files to known working file objects |
| 1241 | in case they have been overwritten with a broken object. However, the |
| 1242 | preferred way to do this is to explicitly save the previous stream before |
| 1243 | replacing it, and restore the saved object. |
Christian Heimes | 58cb1b8 | 2007-11-13 02:19:40 +0000 | [diff] [blame] | 1244 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 1245 | .. note:: |
| 1246 | Under some conditions ``stdin``, ``stdout`` and ``stderr`` as well as the |
| 1247 | original values ``__stdin__``, ``__stdout__`` and ``__stderr__`` can be |
Serhiy Storchaka | ecf41da | 2016-10-19 16:29:26 +0300 | [diff] [blame] | 1248 | ``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] | 1249 | to a console and Python apps started with :program:`pythonw`. |
Christian Heimes | 58cb1b8 | 2007-11-13 02:19:40 +0000 | [diff] [blame] | 1250 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1251 | |
Victor Stinner | d5c355c | 2011-04-30 14:53:09 +0200 | [diff] [blame] | 1252 | .. data:: thread_info |
| 1253 | |
| 1254 | A :term:`struct sequence` holding information about the thread |
| 1255 | implementation. |
| 1256 | |
Georg Brandl | 44ea77b | 2013-03-28 13:28:44 +0100 | [diff] [blame] | 1257 | .. tabularcolumns:: |l|p{0.7\linewidth}| |
| 1258 | |
Victor Stinner | d5c355c | 2011-04-30 14:53:09 +0200 | [diff] [blame] | 1259 | +------------------+---------------------------------------------------------+ |
| 1260 | | Attribute | Explanation | |
| 1261 | +==================+=========================================================+ |
| 1262 | | :const:`name` | Name of the thread implementation: | |
| 1263 | | | | |
| 1264 | | | * ``'nt'``: Windows threads | |
Victor Stinner | d5c355c | 2011-04-30 14:53:09 +0200 | [diff] [blame] | 1265 | | | * ``'pthread'``: POSIX threads | |
| 1266 | | | * ``'solaris'``: Solaris threads | |
| 1267 | +------------------+---------------------------------------------------------+ |
| 1268 | | :const:`lock` | Name of the lock implementation: | |
| 1269 | | | | |
| 1270 | | | * ``'semaphore'``: a lock uses a semaphore | |
| 1271 | | | * ``'mutex+cond'``: a lock uses a mutex | |
| 1272 | | | and a condition variable | |
| 1273 | | | * ``None`` if this information is unknown | |
| 1274 | +------------------+---------------------------------------------------------+ |
| 1275 | | :const:`version` | Name and version of the thread library. It is a string, | |
| 1276 | | | or ``None`` if these informations are unknown. | |
| 1277 | +------------------+---------------------------------------------------------+ |
| 1278 | |
| 1279 | .. versionadded:: 3.3 |
| 1280 | |
| 1281 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1282 | .. data:: tracebacklimit |
| 1283 | |
| 1284 | When this variable is set to an integer value, it determines the maximum number |
| 1285 | of levels of traceback information printed when an unhandled exception occurs. |
| 1286 | The default is ``1000``. When set to ``0`` or less, all traceback information |
| 1287 | is suppressed and only the exception type and value are printed. |
| 1288 | |
| 1289 | |
| 1290 | .. data:: version |
| 1291 | |
| 1292 | A string containing the version number of the Python interpreter plus additional |
Georg Brandl | e42a59d | 2010-07-31 20:05:31 +0000 | [diff] [blame] | 1293 | information on the build number and compiler used. This string is displayed |
| 1294 | when the interactive interpreter is started. Do not extract version information |
| 1295 | out of it, rather, use :data:`version_info` and the functions provided by the |
| 1296 | :mod:`platform` module. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1297 | |
| 1298 | |
| 1299 | .. data:: api_version |
| 1300 | |
| 1301 | The C API version for this interpreter. Programmers may find this useful when |
| 1302 | debugging version conflicts between Python and extension modules. |
| 1303 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1304 | |
| 1305 | .. data:: version_info |
| 1306 | |
| 1307 | A tuple containing the five components of the version number: *major*, *minor*, |
| 1308 | *micro*, *releaselevel*, and *serial*. All values except *releaselevel* are |
| 1309 | integers; the release level is ``'alpha'``, ``'beta'``, ``'candidate'``, or |
| 1310 | ``'final'``. The ``version_info`` value corresponding to the Python version 2.0 |
Eric Smith | 0e5b562 | 2009-02-06 01:32:42 +0000 | [diff] [blame] | 1311 | is ``(2, 0, 0, 'final', 0)``. The components can also be accessed by name, |
| 1312 | so ``sys.version_info[0]`` is equivalent to ``sys.version_info.major`` |
| 1313 | and so on. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1314 | |
Raymond Hettinger | 35a8836 | 2009-04-09 00:08:24 +0000 | [diff] [blame] | 1315 | .. versionchanged:: 3.1 |
Georg Brandl | 67b21b7 | 2010-08-17 15:07:14 +0000 | [diff] [blame] | 1316 | Added named component attributes. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1317 | |
| 1318 | .. data:: warnoptions |
| 1319 | |
| 1320 | This is an implementation detail of the warnings framework; do not modify this |
| 1321 | value. Refer to the :mod:`warnings` module for more information on the warnings |
| 1322 | framework. |
| 1323 | |
| 1324 | |
| 1325 | .. data:: winver |
| 1326 | |
| 1327 | The version number used to form registry keys on Windows platforms. This is |
| 1328 | stored as string resource 1000 in the Python DLL. The value is normally the |
| 1329 | first three characters of :const:`version`. It is provided in the :mod:`sys` |
| 1330 | module for informational purposes; modifying this value has no effect on the |
| 1331 | registry keys used by Python. Availability: Windows. |
Mark Dickinson | be5846b | 2010-07-02 20:26:07 +0000 | [diff] [blame] | 1332 | |
Antoine Pitrou | 9583cac | 2010-10-21 13:42:28 +0000 | [diff] [blame] | 1333 | |
| 1334 | .. data:: _xoptions |
| 1335 | |
| 1336 | A dictionary of the various implementation-specific flags passed through |
| 1337 | the :option:`-X` command-line option. Option names are either mapped to |
Martin Panter | 1050d2d | 2016-07-26 11:18:21 +0200 | [diff] [blame] | 1338 | their values, if given explicitly, or to :const:`True`. Example: |
| 1339 | |
| 1340 | .. code-block:: shell-session |
Antoine Pitrou | 9583cac | 2010-10-21 13:42:28 +0000 | [diff] [blame] | 1341 | |
| 1342 | $ ./python -Xa=b -Xc |
| 1343 | Python 3.2a3+ (py3k, Oct 16 2010, 20:14:50) |
| 1344 | [GCC 4.4.3] on linux2 |
| 1345 | Type "help", "copyright", "credits" or "license" for more information. |
| 1346 | >>> import sys |
| 1347 | >>> sys._xoptions |
| 1348 | {'a': 'b', 'c': True} |
| 1349 | |
| 1350 | .. impl-detail:: |
| 1351 | |
| 1352 | This is a CPython-specific way of accessing options passed through |
| 1353 | :option:`-X`. Other implementations may export them through other |
| 1354 | means, or not at all. |
| 1355 | |
| 1356 | .. versionadded:: 3.2 |
| 1357 | |
| 1358 | |
Mark Dickinson | be5846b | 2010-07-02 20:26:07 +0000 | [diff] [blame] | 1359 | .. rubric:: Citations |
| 1360 | |
Serhiy Storchaka | a4d170d | 2013-12-23 18:20:51 +0200 | [diff] [blame] | 1361 | .. [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\ . |