1:mod:`logging` --- Logging facility for Python 2============================================== 3 4.. module:: logging 5 :synopsis: Flexible event logging system for applications. 6 7.. moduleauthor:: Vinay Sajip <vinay_sajip@red-dove.com> 8.. sectionauthor:: Vinay Sajip <vinay_sajip@red-dove.com> 9 10**Source code:** :source:`Lib/logging/__init__.py` 11 12.. index:: pair: Errors; logging 13 14.. sidebar:: Important 15 16 This page contains the API reference information. For tutorial 17 information and discussion of more advanced topics, see 18 19 * :ref:`Basic Tutorial <logging-basic-tutorial>` 20 * :ref:`Advanced Tutorial <logging-advanced-tutorial>` 21 * :ref:`Logging Cookbook <logging-cookbook>` 22 23-------------- 24 25This module defines functions and classes which implement a flexible event 26logging system for applications and libraries. 27 28The key benefit of having the logging API provided by a standard library module 29is that all Python modules can participate in logging, so your application log 30can include your own messages integrated with messages from third-party 31modules. 32 33The module provides a lot of functionality and flexibility. If you are 34unfamiliar with logging, the best way to get to grips with it is to see the 35tutorials (see the links on the right). 36 37The basic classes defined by the module, together with their functions, are 38listed below. 39 40* Loggers expose the interface that application code directly uses. 41* Handlers send the log records (created by loggers) to the appropriate 42 destination. 43* Filters provide a finer grained facility for determining which log records 44 to output. 45* Formatters specify the layout of log records in the final output. 46 47 48.. _logger: 49 50Logger Objects 51-------------- 52 53Loggers have the following attributes and methods. Note that Loggers should 54*NEVER* be instantiated directly, but always through the module-level function 55``logging.getLogger(name)``. Multiple calls to :func:`getLogger` with the same 56name will always return a reference to the same Logger object. 57 58The ``name`` is potentially a period-separated hierarchical value, like 59``foo.bar.baz`` (though it could also be just plain ``foo``, for example). 60Loggers that are further down in the hierarchical list are children of loggers 61higher up in the list. For example, given a logger with a name of ``foo``, 62loggers with names of ``foo.bar``, ``foo.bar.baz``, and ``foo.bam`` are all 63descendants of ``foo``. The logger name hierarchy is analogous to the Python 64package hierarchy, and identical to it if you organise your loggers on a 65per-module basis using the recommended construction 66``logging.getLogger(__name__)``. That's because in a module, ``__name__`` 67is the module's name in the Python package namespace. 68 69 70.. class:: Logger 71 72 .. attribute:: Logger.propagate 73 74 If this attribute evaluates to true, events logged to this logger will be 75 passed to the handlers of higher level (ancestor) loggers, in addition to 76 any handlers attached to this logger. Messages are passed directly to the 77 ancestor loggers' handlers - neither the level nor filters of the ancestor 78 loggers in question are considered. 79 80 If this evaluates to false, logging messages are not passed to the handlers 81 of ancestor loggers. 82 83 The constructor sets this attribute to ``True``. 84 85 .. note:: If you attach a handler to a logger *and* one or more of its 86 ancestors, it may emit the same record multiple times. In general, you 87 should not need to attach a handler to more than one logger - if you just 88 attach it to the appropriate logger which is highest in the logger 89 hierarchy, then it will see all events logged by all descendant loggers, 90 provided that their propagate setting is left set to ``True``. A common 91 scenario is to attach handlers only to the root logger, and to let 92 propagation take care of the rest. 93 94 .. method:: Logger.setLevel(level) 95 96 Sets the threshold for this logger to *level*. Logging messages which are less 97 severe than *level* will be ignored; logging messages which have severity *level* 98 or higher will be emitted by whichever handler or handlers service this logger, 99 unless a handler's level has been set to a higher severity level than *level*. 100 101 When a logger is created, the level is set to :const:`NOTSET` (which causes 102 all messages to be processed when the logger is the root logger, or delegation 103 to the parent when the logger is a non-root logger). Note that the root logger 104 is created with level :const:`WARNING`. 105 106 The term 'delegation to the parent' means that if a logger has a level of 107 NOTSET, its chain of ancestor loggers is traversed until either an ancestor with 108 a level other than NOTSET is found, or the root is reached. 109 110 If an ancestor is found with a level other than NOTSET, then that ancestor's 111 level is treated as the effective level of the logger where the ancestor search 112 began, and is used to determine how a logging event is handled. 113 114 If the root is reached, and it has a level of NOTSET, then all messages will be 115 processed. Otherwise, the root's level will be used as the effective level. 116 117 See :ref:`levels` for a list of levels. 118 119 .. versionchanged:: 3.2 120 The *level* parameter now accepts a string representation of the 121 level such as 'INFO' as an alternative to the integer constants 122 such as :const:`INFO`. Note, however, that levels are internally stored 123 as integers, and methods such as e.g. :meth:`getEffectiveLevel` and 124 :meth:`isEnabledFor` will return/expect to be passed integers. 125 126 127 .. method:: Logger.isEnabledFor(level) 128 129 Indicates if a message of severity *level* would be processed by this logger. 130 This method checks first the module-level level set by 131 ``logging.disable(level)`` and then the logger's effective level as determined 132 by :meth:`getEffectiveLevel`. 133 134 135 .. method:: Logger.getEffectiveLevel() 136 137 Indicates the effective level for this logger. If a value other than 138 :const:`NOTSET` has been set using :meth:`setLevel`, it is returned. Otherwise, 139 the hierarchy is traversed towards the root until a value other than 140 :const:`NOTSET` is found, and that value is returned. The value returned is 141 an integer, typically one of :const:`logging.DEBUG`, :const:`logging.INFO` 142 etc. 143 144 145 .. method:: Logger.getChild(suffix) 146 147 Returns a logger which is a descendant to this logger, as determined by the suffix. 148 Thus, ``logging.getLogger('abc').getChild('def.ghi')`` would return the same 149 logger as would be returned by ``logging.getLogger('abc.def.ghi')``. This is a 150 convenience method, useful when the parent logger is named using e.g. ``__name__`` 151 rather than a literal string. 152 153 .. versionadded:: 3.2 154 155 156 .. method:: Logger.debug(msg, *args, **kwargs) 157 158 Logs a message with level :const:`DEBUG` on this logger. The *msg* is the 159 message format string, and the *args* are the arguments which are merged into 160 *msg* using the string formatting operator. (Note that this means that you can 161 use keywords in the format string, together with a single dictionary argument.) 162 No % formatting operation is performed on *msg* when no *args* are supplied. 163 164 There are four keyword arguments in *kwargs* which are inspected: 165 *exc_info*, *stack_info*, *stacklevel* and *extra*. 166 167 If *exc_info* does not evaluate as false, it causes exception information to be 168 added to the logging message. If an exception tuple (in the format returned by 169 :func:`sys.exc_info`) or an exception instance is provided, it is used; 170 otherwise, :func:`sys.exc_info` is called to get the exception information. 171 172 The second optional keyword argument is *stack_info*, which defaults to 173 ``False``. If true, stack information is added to the logging 174 message, including the actual logging call. Note that this is not the same 175 stack information as that displayed through specifying *exc_info*: The 176 former is stack frames from the bottom of the stack up to the logging call 177 in the current thread, whereas the latter is information about stack frames 178 which have been unwound, following an exception, while searching for 179 exception handlers. 180 181 You can specify *stack_info* independently of *exc_info*, e.g. to just show 182 how you got to a certain point in your code, even when no exceptions were 183 raised. The stack frames are printed following a header line which says: 184 185 .. code-block:: none 186 187 Stack (most recent call last): 188 189 This mimics the ``Traceback (most recent call last):`` which is used when 190 displaying exception frames. 191 192 The third optional keyword argument is *stacklevel*, which defaults to ``1``. 193 If greater than 1, the corresponding number of stack frames are skipped 194 when computing the line number and function name set in the :class:`LogRecord` 195 created for the logging event. This can be used in logging helpers so that 196 the function name, filename and line number recorded are not the information 197 for the helper function/method, but rather its caller. The name of this 198 parameter mirrors the equivalent one in the :mod:`warnings` module. 199 200 The fourth keyword argument is *extra* which can be used to pass a 201 dictionary which is used to populate the __dict__ of the :class:`LogRecord` 202 created for the logging event with user-defined attributes. These custom 203 attributes can then be used as you like. For example, they could be 204 incorporated into logged messages. For example:: 205 206 FORMAT = '%(asctime)-15s %(clientip)s %(user)-8s %(message)s' 207 logging.basicConfig(format=FORMAT) 208 d = {'clientip': '192.168.0.1', 'user': 'fbloggs'} 209 logger = logging.getLogger('tcpserver') 210 logger.warning('Protocol problem: %s', 'connection reset', extra=d) 211 212 would print something like 213 214 .. code-block:: none 215 216 2006-02-08 22:20:02,165 192.168.0.1 fbloggs Protocol problem: connection reset 217 218 The keys in the dictionary passed in *extra* should not clash with the keys used 219 by the logging system. (See the :class:`Formatter` documentation for more 220 information on which keys are used by the logging system.) 221 222 If you choose to use these attributes in logged messages, you need to exercise 223 some care. In the above example, for instance, the :class:`Formatter` has been 224 set up with a format string which expects 'clientip' and 'user' in the attribute 225 dictionary of the :class:`LogRecord`. If these are missing, the message will 226 not be logged because a string formatting exception will occur. So in this case, 227 you always need to pass the *extra* dictionary with these keys. 228 229 While this might be annoying, this feature is intended for use in specialized 230 circumstances, such as multi-threaded servers where the same code executes in 231 many contexts, and interesting conditions which arise are dependent on this 232 context (such as remote client IP address and authenticated user name, in the 233 above example). In such circumstances, it is likely that specialized 234 :class:`Formatter`\ s would be used with particular :class:`Handler`\ s. 235 236 .. versionchanged:: 3.2 237 The *stack_info* parameter was added. 238 239 .. versionchanged:: 3.5 240 The *exc_info* parameter can now accept exception instances. 241 242 .. versionchanged:: 3.8 243 The *stacklevel* parameter was added. 244 245 246 .. method:: Logger.info(msg, *args, **kwargs) 247 248 Logs a message with level :const:`INFO` on this logger. The arguments are 249 interpreted as for :meth:`debug`. 250 251 252 .. method:: Logger.warning(msg, *args, **kwargs) 253 254 Logs a message with level :const:`WARNING` on this logger. The arguments are 255 interpreted as for :meth:`debug`. 256 257 .. note:: There is an obsolete method ``warn`` which is functionally 258 identical to ``warning``. As ``warn`` is deprecated, please do not use 259 it - use ``warning`` instead. 260 261 .. method:: Logger.error(msg, *args, **kwargs) 262 263 Logs a message with level :const:`ERROR` on this logger. The arguments are 264 interpreted as for :meth:`debug`. 265 266 267 .. method:: Logger.critical(msg, *args, **kwargs) 268 269 Logs a message with level :const:`CRITICAL` on this logger. The arguments are 270 interpreted as for :meth:`debug`. 271 272 273 .. method:: Logger.log(level, msg, *args, **kwargs) 274 275 Logs a message with integer level *level* on this logger. The other arguments are 276 interpreted as for :meth:`debug`. 277 278 279 .. method:: Logger.exception(msg, *args, **kwargs) 280 281 Logs a message with level :const:`ERROR` on this logger. The arguments are 282 interpreted as for :meth:`debug`. Exception info is added to the logging 283 message. This method should only be called from an exception handler. 284 285 286 .. method:: Logger.addFilter(filter) 287 288 Adds the specified filter *filter* to this logger. 289 290 291 .. method:: Logger.removeFilter(filter) 292 293 Removes the specified filter *filter* from this logger. 294 295 296 .. method:: Logger.filter(record) 297 298 Apply this logger's filters to the record and return ``True`` if the 299 record is to be processed. The filters are consulted in turn, until one of 300 them returns a false value. If none of them return a false value, the record 301 will be processed (passed to handlers). If one returns a false value, no 302 further processing of the record occurs. 303 304 305 .. method:: Logger.addHandler(hdlr) 306 307 Adds the specified handler *hdlr* to this logger. 308 309 310 .. method:: Logger.removeHandler(hdlr) 311 312 Removes the specified handler *hdlr* from this logger. 313 314 315 .. method:: Logger.findCaller(stack_info=False, stacklevel=1) 316 317 Finds the caller's source filename and line number. Returns the filename, line 318 number, function name and stack information as a 4-element tuple. The stack 319 information is returned as ``None`` unless *stack_info* is ``True``. 320 321 The *stacklevel* parameter is passed from code calling the :meth:`debug` 322 and other APIs. If greater than 1, the excess is used to skip stack frames 323 before determining the values to be returned. This will generally be useful 324 when calling logging APIs from helper/wrapper code, so that the information 325 in the event log refers not to the helper/wrapper code, but to the code that 326 calls it. 327 328 329 .. method:: Logger.handle(record) 330 331 Handles a record by passing it to all handlers associated with this logger and 332 its ancestors (until a false value of *propagate* is found). This method is used 333 for unpickled records received from a socket, as well as those created locally. 334 Logger-level filtering is applied using :meth:`~Logger.filter`. 335 336 337 .. method:: Logger.makeRecord(name, level, fn, lno, msg, args, exc_info, func=None, extra=None, sinfo=None) 338 339 This is a factory method which can be overridden in subclasses to create 340 specialized :class:`LogRecord` instances. 341 342 .. method:: Logger.hasHandlers() 343 344 Checks to see if this logger has any handlers configured. This is done by 345 looking for handlers in this logger and its parents in the logger hierarchy. 346 Returns ``True`` if a handler was found, else ``False``. The method stops searching 347 up the hierarchy whenever a logger with the 'propagate' attribute set to 348 false is found - that will be the last logger which is checked for the 349 existence of handlers. 350 351 .. versionadded:: 3.2 352 353 .. versionchanged:: 3.7 354 Loggers can now be pickled and unpickled. 355 356.. _levels: 357 358Logging Levels 359-------------- 360 361The numeric values of logging levels are given in the following table. These are 362primarily of interest if you want to define your own levels, and need them to 363have specific values relative to the predefined levels. If you define a level 364with the same numeric value, it overwrites the predefined value; the predefined 365name is lost. 366 367+--------------+---------------+ 368| Level | Numeric value | 369+==============+===============+ 370| ``CRITICAL`` | 50 | 371+--------------+---------------+ 372| ``ERROR`` | 40 | 373+--------------+---------------+ 374| ``WARNING`` | 30 | 375+--------------+---------------+ 376| ``INFO`` | 20 | 377+--------------+---------------+ 378| ``DEBUG`` | 10 | 379+--------------+---------------+ 380| ``NOTSET`` | 0 | 381+--------------+---------------+ 382 383 384.. _handler: 385 386Handler Objects 387--------------- 388 389Handlers have the following attributes and methods. Note that :class:`Handler` 390is never instantiated directly; this class acts as a base for more useful 391subclasses. However, the :meth:`__init__` method in subclasses needs to call 392:meth:`Handler.__init__`. 393 394.. class:: Handler 395 396 .. method:: Handler.__init__(level=NOTSET) 397 398 Initializes the :class:`Handler` instance by setting its level, setting the list 399 of filters to the empty list and creating a lock (using :meth:`createLock`) for 400 serializing access to an I/O mechanism. 401 402 403 .. method:: Handler.createLock() 404 405 Initializes a thread lock which can be used to serialize access to underlying 406 I/O functionality which may not be threadsafe. 407 408 409 .. method:: Handler.acquire() 410 411 Acquires the thread lock created with :meth:`createLock`. 412 413 414 .. method:: Handler.release() 415 416 Releases the thread lock acquired with :meth:`acquire`. 417 418 419 .. method:: Handler.setLevel(level) 420 421 Sets the threshold for this handler to *level*. Logging messages which are 422 less severe than *level* will be ignored. When a handler is created, the 423 level is set to :const:`NOTSET` (which causes all messages to be 424 processed). 425 426 See :ref:`levels` for a list of levels. 427 428 .. versionchanged:: 3.2 429 The *level* parameter now accepts a string representation of the 430 level such as 'INFO' as an alternative to the integer constants 431 such as :const:`INFO`. 432 433 434 .. method:: Handler.setFormatter(fmt) 435 436 Sets the :class:`Formatter` for this handler to *fmt*. 437 438 439 .. method:: Handler.addFilter(filter) 440 441 Adds the specified filter *filter* to this handler. 442 443 444 .. method:: Handler.removeFilter(filter) 445 446 Removes the specified filter *filter* from this handler. 447 448 449 .. method:: Handler.filter(record) 450 451 Apply this handler's filters to the record and return ``True`` if the 452 record is to be processed. The filters are consulted in turn, until one of 453 them returns a false value. If none of them return a false value, the record 454 will be emitted. If one returns a false value, the handler will not emit the 455 record. 456 457 458 .. method:: Handler.flush() 459 460 Ensure all logging output has been flushed. This version does nothing and is 461 intended to be implemented by subclasses. 462 463 464 .. method:: Handler.close() 465 466 Tidy up any resources used by the handler. This version does no output but 467 removes the handler from an internal list of handlers which is closed when 468 :func:`shutdown` is called. Subclasses should ensure that this gets called 469 from overridden :meth:`close` methods. 470 471 472 .. method:: Handler.handle(record) 473 474 Conditionally emits the specified logging record, depending on filters which may 475 have been added to the handler. Wraps the actual emission of the record with 476 acquisition/release of the I/O thread lock. 477 478 479 .. method:: Handler.handleError(record) 480 481 This method should be called from handlers when an exception is encountered 482 during an :meth:`emit` call. If the module-level attribute 483 ``raiseExceptions`` is ``False``, exceptions get silently ignored. This is 484 what is mostly wanted for a logging system - most users will not care about 485 errors in the logging system, they are more interested in application 486 errors. You could, however, replace this with a custom handler if you wish. 487 The specified record is the one which was being processed when the exception 488 occurred. (The default value of ``raiseExceptions`` is ``True``, as that is 489 more useful during development). 490 491 492 .. method:: Handler.format(record) 493 494 Do formatting for a record - if a formatter is set, use it. Otherwise, use the 495 default formatter for the module. 496 497 498 .. method:: Handler.emit(record) 499 500 Do whatever it takes to actually log the specified logging record. This version 501 is intended to be implemented by subclasses and so raises a 502 :exc:`NotImplementedError`. 503 504For a list of handlers included as standard, see :mod:`logging.handlers`. 505 506.. _formatter-objects: 507 508Formatter Objects 509----------------- 510 511.. currentmodule:: logging 512 513:class:`Formatter` objects have the following attributes and methods. They are 514responsible for converting a :class:`LogRecord` to (usually) a string which can 515be interpreted by either a human or an external system. The base 516:class:`Formatter` allows a formatting string to be specified. If none is 517supplied, the default value of ``'%(message)s'`` is used, which just includes 518the message in the logging call. To have additional items of information in the 519formatted output (such as a timestamp), keep reading. 520 521A Formatter can be initialized with a format string which makes use of knowledge 522of the :class:`LogRecord` attributes - such as the default value mentioned above 523making use of the fact that the user's message and arguments are pre-formatted 524into a :class:`LogRecord`'s *message* attribute. This format string contains 525standard Python %-style mapping keys. See section :ref:`old-string-formatting` 526for more information on string formatting. 527 528The useful mapping keys in a :class:`LogRecord` are given in the section on 529:ref:`logrecord-attributes`. 530 531 532.. class:: Formatter(fmt=None, datefmt=None, style='%', validate=True) 533 534 Returns a new instance of the :class:`Formatter` class. The instance is 535 initialized with a format string for the message as a whole, as well as a 536 format string for the date/time portion of a message. If no *fmt* is 537 specified, ``'%(message)s'`` is used. If no *datefmt* is specified, a format 538 is used which is described in the :meth:`formatTime` documentation. 539 540 The *style* parameter can be one of '%', '{' or '$' and determines how 541 the format string will be merged with its data: using one of %-formatting, 542 :meth:`str.format` or :class:`string.Template`. This only applies to the 543 format string *fmt* (e.g. ``'%(message)s'`` or ``{message}``), not to the 544 actual log messages passed to ``Logger.debug`` etc; see 545 :ref:`formatting-styles` for more information on using {- and $-formatting 546 for log messages. 547 548 .. versionchanged:: 3.2 549 The *style* parameter was added. 550 551 .. versionchanged:: 3.8 552 The *validate* parameter was added. Incorrect or mismatched style and fmt 553 will raise a ``ValueError``. 554 For example: ``logging.Formatter('%(asctime)s - %(message)s', style='{')``. 555 556 .. method:: format(record) 557 558 The record's attribute dictionary is used as the operand to a string 559 formatting operation. Returns the resulting string. Before formatting the 560 dictionary, a couple of preparatory steps are carried out. The *message* 561 attribute of the record is computed using *msg* % *args*. If the 562 formatting string contains ``'(asctime)'``, :meth:`formatTime` is called 563 to format the event time. If there is exception information, it is 564 formatted using :meth:`formatException` and appended to the message. Note 565 that the formatted exception information is cached in attribute 566 *exc_text*. This is useful because the exception information can be 567 pickled and sent across the wire, but you should be careful if you have 568 more than one :class:`Formatter` subclass which customizes the formatting 569 of exception information. In this case, you will have to clear the cached 570 value after a formatter has done its formatting, so that the next 571 formatter to handle the event doesn't use the cached value but 572 recalculates it afresh. 573 574 If stack information is available, it's appended after the exception 575 information, using :meth:`formatStack` to transform it if necessary. 576 577 578 .. method:: formatTime(record, datefmt=None) 579 580 This method should be called from :meth:`format` by a formatter which 581 wants to make use of a formatted time. This method can be overridden in 582 formatters to provide for any specific requirement, but the basic behavior 583 is as follows: if *datefmt* (a string) is specified, it is used with 584 :func:`time.strftime` to format the creation time of the 585 record. Otherwise, the format '%Y-%m-%d %H:%M:%S,uuu' is used, where the 586 uuu part is a millisecond value and the other letters are as per the 587 :func:`time.strftime` documentation. An example time in this format is 588 ``2003-01-23 00:29:50,411``. The resulting string is returned. 589 590 This function uses a user-configurable function to convert the creation 591 time to a tuple. By default, :func:`time.localtime` is used; to change 592 this for a particular formatter instance, set the ``converter`` attribute 593 to a function with the same signature as :func:`time.localtime` or 594 :func:`time.gmtime`. To change it for all formatters, for example if you 595 want all logging times to be shown in GMT, set the ``converter`` 596 attribute in the ``Formatter`` class. 597 598 .. versionchanged:: 3.3 599 Previously, the default format was hard-coded as in this example: 600 ``2010-09-06 22:38:15,292`` where the part before the comma is 601 handled by a strptime format string (``'%Y-%m-%d %H:%M:%S'``), and the 602 part after the comma is a millisecond value. Because strptime does not 603 have a format placeholder for milliseconds, the millisecond value is 604 appended using another format string, ``'%s,%03d'`` --- and both of these 605 format strings have been hardcoded into this method. With the change, 606 these strings are defined as class-level attributes which can be 607 overridden at the instance level when desired. The names of the 608 attributes are ``default_time_format`` (for the strptime format string) 609 and ``default_msec_format`` (for appending the millisecond value). 610 611 .. versionchanged:: 3.9 612 The ``default_msec_format`` can be ``None``. 613 614 .. method:: formatException(exc_info) 615 616 Formats the specified exception information (a standard exception tuple as 617 returned by :func:`sys.exc_info`) as a string. This default implementation 618 just uses :func:`traceback.print_exception`. The resulting string is 619 returned. 620 621 .. method:: formatStack(stack_info) 622 623 Formats the specified stack information (a string as returned by 624 :func:`traceback.print_stack`, but with the last newline removed) as a 625 string. This default implementation just returns the input value. 626 627.. _filter: 628 629Filter Objects 630-------------- 631 632``Filters`` can be used by ``Handlers`` and ``Loggers`` for more sophisticated 633filtering than is provided by levels. The base filter class only allows events 634which are below a certain point in the logger hierarchy. For example, a filter 635initialized with 'A.B' will allow events logged by loggers 'A.B', 'A.B.C', 636'A.B.C.D', 'A.B.D' etc. but not 'A.BB', 'B.A.B' etc. If initialized with the 637empty string, all events are passed. 638 639 640.. class:: Filter(name='') 641 642 Returns an instance of the :class:`Filter` class. If *name* is specified, it 643 names a logger which, together with its children, will have its events allowed 644 through the filter. If *name* is the empty string, allows every event. 645 646 647 .. method:: filter(record) 648 649 Is the specified record to be logged? Returns zero for no, nonzero for 650 yes. If deemed appropriate, the record may be modified in-place by this 651 method. 652 653Note that filters attached to handlers are consulted before an event is 654emitted by the handler, whereas filters attached to loggers are consulted 655whenever an event is logged (using :meth:`debug`, :meth:`info`, 656etc.), before sending an event to handlers. This means that events which have 657been generated by descendant loggers will not be filtered by a logger's filter 658setting, unless the filter has also been applied to those descendant loggers. 659 660You don't actually need to subclass ``Filter``: you can pass any instance 661which has a ``filter`` method with the same semantics. 662 663.. versionchanged:: 3.2 664 You don't need to create specialized ``Filter`` classes, or use other 665 classes with a ``filter`` method: you can use a function (or other 666 callable) as a filter. The filtering logic will check to see if the filter 667 object has a ``filter`` attribute: if it does, it's assumed to be a 668 ``Filter`` and its :meth:`~Filter.filter` method is called. Otherwise, it's 669 assumed to be a callable and called with the record as the single 670 parameter. The returned value should conform to that returned by 671 :meth:`~Filter.filter`. 672 673Although filters are used primarily to filter records based on more 674sophisticated criteria than levels, they get to see every record which is 675processed by the handler or logger they're attached to: this can be useful if 676you want to do things like counting how many records were processed by a 677particular logger or handler, or adding, changing or removing attributes in 678the :class:`LogRecord` being processed. Obviously changing the LogRecord needs 679to be done with some care, but it does allow the injection of contextual 680information into logs (see :ref:`filters-contextual`). 681 682.. _log-record: 683 684LogRecord Objects 685----------------- 686 687:class:`LogRecord` instances are created automatically by the :class:`Logger` 688every time something is logged, and can be created manually via 689:func:`makeLogRecord` (for example, from a pickled event received over the 690wire). 691 692 693.. class:: LogRecord(name, level, pathname, lineno, msg, args, exc_info, func=None, sinfo=None) 694 695 Contains all the information pertinent to the event being logged. 696 697 The primary information is passed in :attr:`msg` and :attr:`args`, which 698 are combined using ``msg % args`` to create the :attr:`message` field of the 699 record. 700 701 :param name: The name of the logger used to log the event represented by 702 this LogRecord. Note that this name will always have this 703 value, even though it may be emitted by a handler attached to 704 a different (ancestor) logger. 705 :param level: The numeric level of the logging event (one of DEBUG, INFO etc.) 706 Note that this is converted to *two* attributes of the LogRecord: 707 ``levelno`` for the numeric value and ``levelname`` for the 708 corresponding level name. 709 :param pathname: The full pathname of the source file where the logging call 710 was made. 711 :param lineno: The line number in the source file where the logging call was 712 made. 713 :param msg: The event description message, possibly a format string with 714 placeholders for variable data. 715 :param args: Variable data to merge into the *msg* argument to obtain the 716 event description. 717 :param exc_info: An exception tuple with the current exception information, 718 or ``None`` if no exception information is available. 719 :param func: The name of the function or method from which the logging call 720 was invoked. 721 :param sinfo: A text string representing stack information from the base of 722 the stack in the current thread, up to the logging call. 723 724 .. method:: getMessage() 725 726 Returns the message for this :class:`LogRecord` instance after merging any 727 user-supplied arguments with the message. If the user-supplied message 728 argument to the logging call is not a string, :func:`str` is called on it to 729 convert it to a string. This allows use of user-defined classes as 730 messages, whose ``__str__`` method can return the actual format string to 731 be used. 732 733 .. versionchanged:: 3.2 734 The creation of a :class:`LogRecord` has been made more configurable by 735 providing a factory which is used to create the record. The factory can be 736 set using :func:`getLogRecordFactory` and :func:`setLogRecordFactory` 737 (see this for the factory's signature). 738 739 This functionality can be used to inject your own values into a 740 :class:`LogRecord` at creation time. You can use the following pattern:: 741 742 old_factory = logging.getLogRecordFactory() 743 744 def record_factory(*args, **kwargs): 745 record = old_factory(*args, **kwargs) 746 record.custom_attribute = 0xdecafbad 747 return record 748 749 logging.setLogRecordFactory(record_factory) 750 751 With this pattern, multiple factories could be chained, and as long 752 as they don't overwrite each other's attributes or unintentionally 753 overwrite the standard attributes listed above, there should be no 754 surprises. 755 756 757.. _logrecord-attributes: 758 759LogRecord attributes 760-------------------- 761 762The LogRecord has a number of attributes, most of which are derived from the 763parameters to the constructor. (Note that the names do not always correspond 764exactly between the LogRecord constructor parameters and the LogRecord 765attributes.) These attributes can be used to merge data from the record into 766the format string. The following table lists (in alphabetical order) the 767attribute names, their meanings and the corresponding placeholder in a %-style 768format string. 769 770If you are using {}-formatting (:func:`str.format`), you can use 771``{attrname}`` as the placeholder in the format string. If you are using 772$-formatting (:class:`string.Template`), use the form ``${attrname}``. In 773both cases, of course, replace ``attrname`` with the actual attribute name 774you want to use. 775 776In the case of {}-formatting, you can specify formatting flags by placing them 777after the attribute name, separated from it with a colon. For example: a 778placeholder of ``{msecs:03d}`` would format a millisecond value of ``4`` as 779``004``. Refer to the :meth:`str.format` documentation for full details on 780the options available to you. 781 782+----------------+-------------------------+-----------------------------------------------+ 783| Attribute name | Format | Description | 784+================+=========================+===============================================+ 785| args | You shouldn't need to | The tuple of arguments merged into ``msg`` to | 786| | format this yourself. | produce ``message``, or a dict whose values | 787| | | are used for the merge (when there is only one| 788| | | argument, and it is a dictionary). | 789+----------------+-------------------------+-----------------------------------------------+ 790| asctime | ``%(asctime)s`` | Human-readable time when the | 791| | | :class:`LogRecord` was created. By default | 792| | | this is of the form '2003-07-08 16:49:45,896' | 793| | | (the numbers after the comma are millisecond | 794| | | portion of the time). | 795+----------------+-------------------------+-----------------------------------------------+ 796| created | ``%(created)f`` | Time when the :class:`LogRecord` was created | 797| | | (as returned by :func:`time.time`). | 798+----------------+-------------------------+-----------------------------------------------+ 799| exc_info | You shouldn't need to | Exception tuple (à la ``sys.exc_info``) or, | 800| | format this yourself. | if no exception has occurred, ``None``. | 801+----------------+-------------------------+-----------------------------------------------+ 802| filename | ``%(filename)s`` | Filename portion of ``pathname``. | 803+----------------+-------------------------+-----------------------------------------------+ 804| funcName | ``%(funcName)s`` | Name of function containing the logging call. | 805+----------------+-------------------------+-----------------------------------------------+ 806| levelname | ``%(levelname)s`` | Text logging level for the message | 807| | | (``'DEBUG'``, ``'INFO'``, ``'WARNING'``, | 808| | | ``'ERROR'``, ``'CRITICAL'``). | 809+----------------+-------------------------+-----------------------------------------------+ 810| levelno | ``%(levelno)s`` | Numeric logging level for the message | 811| | | (:const:`DEBUG`, :const:`INFO`, | 812| | | :const:`WARNING`, :const:`ERROR`, | 813| | | :const:`CRITICAL`). | 814+----------------+-------------------------+-----------------------------------------------+ 815| lineno | ``%(lineno)d`` | Source line number where the logging call was | 816| | | issued (if available). | 817+----------------+-------------------------+-----------------------------------------------+ 818| message | ``%(message)s`` | The logged message, computed as ``msg % | 819| | | args``. This is set when | 820| | | :meth:`Formatter.format` is invoked. | 821+----------------+-------------------------+-----------------------------------------------+ 822| module | ``%(module)s`` | Module (name portion of ``filename``). | 823+----------------+-------------------------+-----------------------------------------------+ 824| msecs | ``%(msecs)d`` | Millisecond portion of the time when the | 825| | | :class:`LogRecord` was created. | 826+----------------+-------------------------+-----------------------------------------------+ 827| msg | You shouldn't need to | The format string passed in the original | 828| | format this yourself. | logging call. Merged with ``args`` to | 829| | | produce ``message``, or an arbitrary object | 830| | | (see :ref:`arbitrary-object-messages`). | 831+----------------+-------------------------+-----------------------------------------------+ 832| name | ``%(name)s`` | Name of the logger used to log the call. | 833+----------------+-------------------------+-----------------------------------------------+ 834| pathname | ``%(pathname)s`` | Full pathname of the source file where the | 835| | | logging call was issued (if available). | 836+----------------+-------------------------+-----------------------------------------------+ 837| process | ``%(process)d`` | Process ID (if available). | 838+----------------+-------------------------+-----------------------------------------------+ 839| processName | ``%(processName)s`` | Process name (if available). | 840+----------------+-------------------------+-----------------------------------------------+ 841| relativeCreated| ``%(relativeCreated)d`` | Time in milliseconds when the LogRecord was | 842| | | created, relative to the time the logging | 843| | | module was loaded. | 844+----------------+-------------------------+-----------------------------------------------+ 845| stack_info | You shouldn't need to | Stack frame information (where available) | 846| | format this yourself. | from the bottom of the stack in the current | 847| | | thread, up to and including the stack frame | 848| | | of the logging call which resulted in the | 849| | | creation of this record. | 850+----------------+-------------------------+-----------------------------------------------+ 851| thread | ``%(thread)d`` | Thread ID (if available). | 852+----------------+-------------------------+-----------------------------------------------+ 853| threadName | ``%(threadName)s`` | Thread name (if available). | 854+----------------+-------------------------+-----------------------------------------------+ 855 856.. versionchanged:: 3.1 857 *processName* was added. 858 859 860.. _logger-adapter: 861 862LoggerAdapter Objects 863--------------------- 864 865:class:`LoggerAdapter` instances are used to conveniently pass contextual 866information into logging calls. For a usage example, see the section on 867:ref:`adding contextual information to your logging output <context-info>`. 868 869.. class:: LoggerAdapter(logger, extra) 870 871 Returns an instance of :class:`LoggerAdapter` initialized with an 872 underlying :class:`Logger` instance and a dict-like object. 873 874 .. method:: process(msg, kwargs) 875 876 Modifies the message and/or keyword arguments passed to a logging call in 877 order to insert contextual information. This implementation takes the object 878 passed as *extra* to the constructor and adds it to *kwargs* using key 879 'extra'. The return value is a (*msg*, *kwargs*) tuple which has the 880 (possibly modified) versions of the arguments passed in. 881 882In addition to the above, :class:`LoggerAdapter` supports the following 883methods of :class:`Logger`: :meth:`~Logger.debug`, :meth:`~Logger.info`, 884:meth:`~Logger.warning`, :meth:`~Logger.error`, :meth:`~Logger.exception`, 885:meth:`~Logger.critical`, :meth:`~Logger.log`, :meth:`~Logger.isEnabledFor`, 886:meth:`~Logger.getEffectiveLevel`, :meth:`~Logger.setLevel` and 887:meth:`~Logger.hasHandlers`. These methods have the same signatures as their 888counterparts in :class:`Logger`, so you can use the two types of instances 889interchangeably. 890 891.. versionchanged:: 3.2 892 The :meth:`~Logger.isEnabledFor`, :meth:`~Logger.getEffectiveLevel`, 893 :meth:`~Logger.setLevel` and :meth:`~Logger.hasHandlers` methods were added 894 to :class:`LoggerAdapter`. These methods delegate to the underlying logger. 895 896 897Thread Safety 898------------- 899 900The logging module is intended to be thread-safe without any special work 901needing to be done by its clients. It achieves this though using threading 902locks; there is one lock to serialize access to the module's shared data, and 903each handler also creates a lock to serialize access to its underlying I/O. 904 905If you are implementing asynchronous signal handlers using the :mod:`signal` 906module, you may not be able to use logging from within such handlers. This is 907because lock implementations in the :mod:`threading` module are not always 908re-entrant, and so cannot be invoked from such signal handlers. 909 910 911Module-Level Functions 912---------------------- 913 914In addition to the classes described above, there are a number of module-level 915functions. 916 917 918.. function:: getLogger(name=None) 919 920 Return a logger with the specified name or, if name is ``None``, return a 921 logger which is the root logger of the hierarchy. If specified, the name is 922 typically a dot-separated hierarchical name like *'a'*, *'a.b'* or *'a.b.c.d'*. 923 Choice of these names is entirely up to the developer who is using logging. 924 925 All calls to this function with a given name return the same logger instance. 926 This means that logger instances never need to be passed between different parts 927 of an application. 928 929 930.. function:: getLoggerClass() 931 932 Return either the standard :class:`Logger` class, or the last class passed to 933 :func:`setLoggerClass`. This function may be called from within a new class 934 definition, to ensure that installing a customized :class:`Logger` class will 935 not undo customizations already applied by other code. For example:: 936 937 class MyLogger(logging.getLoggerClass()): 938 # ... override behaviour here 939 940 941.. function:: getLogRecordFactory() 942 943 Return a callable which is used to create a :class:`LogRecord`. 944 945 .. versionadded:: 3.2 946 This function has been provided, along with :func:`setLogRecordFactory`, 947 to allow developers more control over how the :class:`LogRecord` 948 representing a logging event is constructed. 949 950 See :func:`setLogRecordFactory` for more information about the how the 951 factory is called. 952 953.. function:: debug(msg, *args, **kwargs) 954 955 Logs a message with level :const:`DEBUG` on the root logger. The *msg* is the 956 message format string, and the *args* are the arguments which are merged into 957 *msg* using the string formatting operator. (Note that this means that you can 958 use keywords in the format string, together with a single dictionary argument.) 959 960 There are three keyword arguments in *kwargs* which are inspected: *exc_info* 961 which, if it does not evaluate as false, causes exception information to be 962 added to the logging message. If an exception tuple (in the format returned by 963 :func:`sys.exc_info`) or an exception instance is provided, it is used; 964 otherwise, :func:`sys.exc_info` is called to get the exception information. 965 966 The second optional keyword argument is *stack_info*, which defaults to 967 ``False``. If true, stack information is added to the logging 968 message, including the actual logging call. Note that this is not the same 969 stack information as that displayed through specifying *exc_info*: The 970 former is stack frames from the bottom of the stack up to the logging call 971 in the current thread, whereas the latter is information about stack frames 972 which have been unwound, following an exception, while searching for 973 exception handlers. 974 975 You can specify *stack_info* independently of *exc_info*, e.g. to just show 976 how you got to a certain point in your code, even when no exceptions were 977 raised. The stack frames are printed following a header line which says: 978 979 .. code-block:: none 980 981 Stack (most recent call last): 982 983 This mimics the ``Traceback (most recent call last):`` which is used when 984 displaying exception frames. 985 986 The third optional keyword argument is *extra* which can be used to pass a 987 dictionary which is used to populate the __dict__ of the LogRecord created for 988 the logging event with user-defined attributes. These custom attributes can then 989 be used as you like. For example, they could be incorporated into logged 990 messages. For example:: 991 992 FORMAT = '%(asctime)-15s %(clientip)s %(user)-8s %(message)s' 993 logging.basicConfig(format=FORMAT) 994 d = {'clientip': '192.168.0.1', 'user': 'fbloggs'} 995 logging.warning('Protocol problem: %s', 'connection reset', extra=d) 996 997 would print something like: 998 999 .. code-block:: none 1000 1001 2006-02-08 22:20:02,165 192.168.0.1 fbloggs Protocol problem: connection reset 1002 1003 The keys in the dictionary passed in *extra* should not clash with the keys used 1004 by the logging system. (See the :class:`Formatter` documentation for more 1005 information on which keys are used by the logging system.) 1006 1007 If you choose to use these attributes in logged messages, you need to exercise 1008 some care. In the above example, for instance, the :class:`Formatter` has been 1009 set up with a format string which expects 'clientip' and 'user' in the attribute 1010 dictionary of the LogRecord. If these are missing, the message will not be 1011 logged because a string formatting exception will occur. So in this case, you 1012 always need to pass the *extra* dictionary with these keys. 1013 1014 While this might be annoying, this feature is intended for use in specialized 1015 circumstances, such as multi-threaded servers where the same code executes in 1016 many contexts, and interesting conditions which arise are dependent on this 1017 context (such as remote client IP address and authenticated user name, in the 1018 above example). In such circumstances, it is likely that specialized 1019 :class:`Formatter`\ s would be used with particular :class:`Handler`\ s. 1020 1021 .. versionchanged:: 3.2 1022 The *stack_info* parameter was added. 1023 1024.. function:: info(msg, *args, **kwargs) 1025 1026 Logs a message with level :const:`INFO` on the root logger. The arguments are 1027 interpreted as for :func:`debug`. 1028 1029 1030.. function:: warning(msg, *args, **kwargs) 1031 1032 Logs a message with level :const:`WARNING` on the root logger. The arguments 1033 are interpreted as for :func:`debug`. 1034 1035 .. note:: There is an obsolete function ``warn`` which is functionally 1036 identical to ``warning``. As ``warn`` is deprecated, please do not use 1037 it - use ``warning`` instead. 1038 1039 1040.. function:: error(msg, *args, **kwargs) 1041 1042 Logs a message with level :const:`ERROR` on the root logger. The arguments are 1043 interpreted as for :func:`debug`. 1044 1045 1046.. function:: critical(msg, *args, **kwargs) 1047 1048 Logs a message with level :const:`CRITICAL` on the root logger. The arguments 1049 are interpreted as for :func:`debug`. 1050 1051 1052.. function:: exception(msg, *args, **kwargs) 1053 1054 Logs a message with level :const:`ERROR` on the root logger. The arguments are 1055 interpreted as for :func:`debug`. Exception info is added to the logging 1056 message. This function should only be called from an exception handler. 1057 1058.. function:: log(level, msg, *args, **kwargs) 1059 1060 Logs a message with level *level* on the root logger. The other arguments are 1061 interpreted as for :func:`debug`. 1062 1063 .. note:: The above module-level convenience functions, which delegate to the 1064 root logger, call :func:`basicConfig` to ensure that at least one handler 1065 is available. Because of this, they should *not* be used in threads, 1066 in versions of Python earlier than 2.7.1 and 3.2, unless at least one 1067 handler has been added to the root logger *before* the threads are 1068 started. In earlier versions of Python, due to a thread safety shortcoming 1069 in :func:`basicConfig`, this can (under rare circumstances) lead to 1070 handlers being added multiple times to the root logger, which can in turn 1071 lead to multiple messages for the same event. 1072 1073.. function:: disable(level=CRITICAL) 1074 1075 Provides an overriding level *level* for all loggers which takes precedence over 1076 the logger's own level. When the need arises to temporarily throttle logging 1077 output down across the whole application, this function can be useful. Its 1078 effect is to disable all logging calls of severity *level* and below, so that 1079 if you call it with a value of INFO, then all INFO and DEBUG events would be 1080 discarded, whereas those of severity WARNING and above would be processed 1081 according to the logger's effective level. If 1082 ``logging.disable(logging.NOTSET)`` is called, it effectively removes this 1083 overriding level, so that logging output again depends on the effective 1084 levels of individual loggers. 1085 1086 Note that if you have defined any custom logging level higher than 1087 ``CRITICAL`` (this is not recommended), you won't be able to rely on the 1088 default value for the *level* parameter, but will have to explicitly supply a 1089 suitable value. 1090 1091 .. versionchanged:: 3.7 1092 The *level* parameter was defaulted to level ``CRITICAL``. See 1093 :issue:`28524` for more information about this change. 1094 1095.. function:: addLevelName(level, levelName) 1096 1097 Associates level *level* with text *levelName* in an internal dictionary, which is 1098 used to map numeric levels to a textual representation, for example when a 1099 :class:`Formatter` formats a message. This function can also be used to define 1100 your own levels. The only constraints are that all levels used must be 1101 registered using this function, levels should be positive integers and they 1102 should increase in increasing order of severity. 1103 1104 .. note:: If you are thinking of defining your own levels, please see the 1105 section on :ref:`custom-levels`. 1106 1107.. function:: getLevelName(level) 1108 1109 Returns the textual representation of logging level *level*. If the level is one 1110 of the predefined levels :const:`CRITICAL`, :const:`ERROR`, :const:`WARNING`, 1111 :const:`INFO` or :const:`DEBUG` then you get the corresponding string. If you 1112 have associated levels with names using :func:`addLevelName` then the name you 1113 have associated with *level* is returned. If a numeric value corresponding to one 1114 of the defined levels is passed in, the corresponding string representation is 1115 returned. Otherwise, the string 'Level %s' % level is returned. 1116 1117 .. note:: Levels are internally integers (as they need to be compared in the 1118 logging logic). This function is used to convert between an integer level 1119 and the level name displayed in the formatted log output by means of the 1120 ``%(levelname)s`` format specifier (see :ref:`logrecord-attributes`). 1121 1122 .. versionchanged:: 3.4 1123 In Python versions earlier than 3.4, this function could also be passed a 1124 text level, and would return the corresponding numeric value of the level. 1125 This undocumented behaviour was considered a mistake, and was removed in 1126 Python 3.4, but reinstated in 3.4.2 due to retain backward compatibility. 1127 1128.. function:: makeLogRecord(attrdict) 1129 1130 Creates and returns a new :class:`LogRecord` instance whose attributes are 1131 defined by *attrdict*. This function is useful for taking a pickled 1132 :class:`LogRecord` attribute dictionary, sent over a socket, and reconstituting 1133 it as a :class:`LogRecord` instance at the receiving end. 1134 1135 1136.. function:: basicConfig(**kwargs) 1137 1138 Does basic configuration for the logging system by creating a 1139 :class:`StreamHandler` with a default :class:`Formatter` and adding it to the 1140 root logger. The functions :func:`debug`, :func:`info`, :func:`warning`, 1141 :func:`error` and :func:`critical` will call :func:`basicConfig` automatically 1142 if no handlers are defined for the root logger. 1143 1144 This function does nothing if the root logger already has handlers 1145 configured, unless the keyword argument *force* is set to ``True``. 1146 1147 .. note:: This function should be called from the main thread 1148 before other threads are started. In versions of Python prior to 1149 2.7.1 and 3.2, if this function is called from multiple threads, 1150 it is possible (in rare circumstances) that a handler will be added 1151 to the root logger more than once, leading to unexpected results 1152 such as messages being duplicated in the log. 1153 1154 The following keyword arguments are supported. 1155 1156 .. tabularcolumns:: |l|L| 1157 1158 +--------------+---------------------------------------------+ 1159 | Format | Description | 1160 +==============+=============================================+ 1161 | *filename* | Specifies that a FileHandler be created, | 1162 | | using the specified filename, rather than a | 1163 | | StreamHandler. | 1164 +--------------+---------------------------------------------+ 1165 | *filemode* | If *filename* is specified, open the file | 1166 | | in this :ref:`mode <filemodes>`. Defaults | 1167 | | to ``'a'``. | 1168 +--------------+---------------------------------------------+ 1169 | *format* | Use the specified format string for the | 1170 | | handler. | 1171 +--------------+---------------------------------------------+ 1172 | *datefmt* | Use the specified date/time format, as | 1173 | | accepted by :func:`time.strftime`. | 1174 +--------------+---------------------------------------------+ 1175 | *style* | If *format* is specified, use this style | 1176 | | for the format string. One of ``'%'``, | 1177 | | ``'{'`` or ``'$'`` for :ref:`printf-style | 1178 | | <old-string-formatting>`, | 1179 | | :meth:`str.format` or | 1180 | | :class:`string.Template` respectively. | 1181 | | Defaults to ``'%'``. | 1182 +--------------+---------------------------------------------+ 1183 | *level* | Set the root logger level to the specified | 1184 | | :ref:`level <levels>`. | 1185 +--------------+---------------------------------------------+ 1186 | *stream* | Use the specified stream to initialize the | 1187 | | StreamHandler. Note that this argument is | 1188 | | incompatible with *filename* - if both | 1189 | | are present, a ``ValueError`` is raised. | 1190 +--------------+---------------------------------------------+ 1191 | *handlers* | If specified, this should be an iterable of | 1192 | | already created handlers to add to the root | 1193 | | logger. Any handlers which don't already | 1194 | | have a formatter set will be assigned the | 1195 | | default formatter created in this function. | 1196 | | Note that this argument is incompatible | 1197 | | with *filename* or *stream* - if both | 1198 | | are present, a ``ValueError`` is raised. | 1199 +--------------+---------------------------------------------+ 1200 | *force* | If this keyword argument is specified as | 1201 | | true, any existing handlers attached to the | 1202 | | root logger are removed and closed, before | 1203 | | carrying out the configuration as specified | 1204 | | by the other arguments. | 1205 +--------------+---------------------------------------------+ 1206 | *encoding* | If this keyword argument is specified along | 1207 | | with *filename*, its value is used when the | 1208 | | FileHandler is created, and thus used when | 1209 | | opening the output file. | 1210 +--------------+---------------------------------------------+ 1211 | *errors* | If this keyword argument is specified along | 1212 | | with *filename*, its value is used when the | 1213 | | FileHandler is created, and thus used when | 1214 | | opening the output file. If not specified, | 1215 | | the value 'backslashreplace' is used. Note | 1216 | | that if ``None`` is specified, it will be | 1217 | | passed as such to func:`open`, which means | 1218 | | that it will be treated the same as passing | 1219 | | 'errors'. | 1220 +--------------+---------------------------------------------+ 1221 1222 .. versionchanged:: 3.2 1223 The *style* argument was added. 1224 1225 .. versionchanged:: 3.3 1226 The *handlers* argument was added. Additional checks were added to 1227 catch situations where incompatible arguments are specified (e.g. 1228 *handlers* together with *stream* or *filename*, or *stream* 1229 together with *filename*). 1230 1231 .. versionchanged:: 3.8 1232 The *force* argument was added. 1233 1234 .. versionchanged:: 3.9 1235 The *encoding* and *errors* arguments were added. 1236 1237.. function:: shutdown() 1238 1239 Informs the logging system to perform an orderly shutdown by flushing and 1240 closing all handlers. This should be called at application exit and no 1241 further use of the logging system should be made after this call. 1242 1243 When the logging module is imported, it registers this function as an exit 1244 handler (see :mod:`atexit`), so normally there's no need to do that 1245 manually. 1246 1247 1248.. function:: setLoggerClass(klass) 1249 1250 Tells the logging system to use the class *klass* when instantiating a logger. 1251 The class should define :meth:`__init__` such that only a name argument is 1252 required, and the :meth:`__init__` should call :meth:`Logger.__init__`. This 1253 function is typically called before any loggers are instantiated by applications 1254 which need to use custom logger behavior. After this call, as at any other 1255 time, do not instantiate loggers directly using the subclass: continue to use 1256 the :func:`logging.getLogger` API to get your loggers. 1257 1258 1259.. function:: setLogRecordFactory(factory) 1260 1261 Set a callable which is used to create a :class:`LogRecord`. 1262 1263 :param factory: The factory callable to be used to instantiate a log record. 1264 1265 .. versionadded:: 3.2 1266 This function has been provided, along with :func:`getLogRecordFactory`, to 1267 allow developers more control over how the :class:`LogRecord` representing 1268 a logging event is constructed. 1269 1270 The factory has the following signature: 1271 1272 ``factory(name, level, fn, lno, msg, args, exc_info, func=None, sinfo=None, **kwargs)`` 1273 1274 :name: The logger name. 1275 :level: The logging level (numeric). 1276 :fn: The full pathname of the file where the logging call was made. 1277 :lno: The line number in the file where the logging call was made. 1278 :msg: The logging message. 1279 :args: The arguments for the logging message. 1280 :exc_info: An exception tuple, or ``None``. 1281 :func: The name of the function or method which invoked the logging 1282 call. 1283 :sinfo: A stack traceback such as is provided by 1284 :func:`traceback.print_stack`, showing the call hierarchy. 1285 :kwargs: Additional keyword arguments. 1286 1287 1288Module-Level Attributes 1289----------------------- 1290 1291.. attribute:: lastResort 1292 1293 A "handler of last resort" is available through this attribute. This 1294 is a :class:`StreamHandler` writing to ``sys.stderr`` with a level of 1295 ``WARNING``, and is used to handle logging events in the absence of any 1296 logging configuration. The end result is to just print the message to 1297 ``sys.stderr``. This replaces the earlier error message saying that 1298 "no handlers could be found for logger XYZ". If you need the earlier 1299 behaviour for some reason, ``lastResort`` can be set to ``None``. 1300 1301 .. versionadded:: 3.2 1302 1303Integration with the warnings module 1304------------------------------------ 1305 1306The :func:`captureWarnings` function can be used to integrate :mod:`logging` 1307with the :mod:`warnings` module. 1308 1309.. function:: captureWarnings(capture) 1310 1311 This function is used to turn the capture of warnings by logging on and 1312 off. 1313 1314 If *capture* is ``True``, warnings issued by the :mod:`warnings` module will 1315 be redirected to the logging system. Specifically, a warning will be 1316 formatted using :func:`warnings.formatwarning` and the resulting string 1317 logged to a logger named ``'py.warnings'`` with a severity of :const:`WARNING`. 1318 1319 If *capture* is ``False``, the redirection of warnings to the logging system 1320 will stop, and warnings will be redirected to their original destinations 1321 (i.e. those in effect before ``captureWarnings(True)`` was called). 1322 1323 1324.. seealso:: 1325 1326 Module :mod:`logging.config` 1327 Configuration API for the logging module. 1328 1329 Module :mod:`logging.handlers` 1330 Useful handlers included with the logging module. 1331 1332 :pep:`282` - A Logging System 1333 The proposal which described this feature for inclusion in the Python standard 1334 library. 1335 1336 `Original Python logging package <https://www.red-dove.com/python_logging.html>`_ 1337 This is the original source for the :mod:`logging` package. The version of the 1338 package available from this site is suitable for use with Python 1.5.2, 2.1.x 1339 and 2.2.x, which do not include the :mod:`logging` package in the standard 1340 library. 1341