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