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 Spelling it out with an example: If the propagate attribute of the logger named 84 ``A.B.C`` evaluates to true, any event logged to ``A.B.C`` via a method call such as 85 ``logging.getLogger('A.B.C').error(...)`` will [subject to passing that logger's 86 level and filter settings] be passed in turn to any handlers attached to loggers 87 named ``A.B``, ``A`` and the root logger, after first being passed to any handlers 88 attached to ``A.B.C``. If any logger in the chain ``A.B.C``, ``A.B``, ``A`` has its 89 ``propagate`` attribute set to false, then that is the last logger whose handlers 90 are offered the event to handle, and propagation stops at that point. 91 92 The constructor sets this attribute to ``True``. 93 94 .. note:: If you attach a handler to a logger *and* one or more of its 95 ancestors, it may emit the same record multiple times. In general, you 96 should not need to attach a handler to more than one logger - if you just 97 attach it to the appropriate logger which is highest in the logger 98 hierarchy, then it will see all events logged by all descendant loggers, 99 provided that their propagate setting is left set to ``True``. A common 100 scenario is to attach handlers only to the root logger, and to let 101 propagation take care of the rest. 102 103 .. method:: Logger.setLevel(level) 104 105 Sets the threshold for this logger to *level*. Logging messages which are less 106 severe than *level* will be ignored; logging messages which have severity *level* 107 or higher will be emitted by whichever handler or handlers service this logger, 108 unless a handler's level has been set to a higher severity level than *level*. 109 110 When a logger is created, the level is set to :const:`NOTSET` (which causes 111 all messages to be processed when the logger is the root logger, or delegation 112 to the parent when the logger is a non-root logger). Note that the root logger 113 is created with level :const:`WARNING`. 114 115 The term 'delegation to the parent' means that if a logger has a level of 116 NOTSET, its chain of ancestor loggers is traversed until either an ancestor with 117 a level other than NOTSET is found, or the root is reached. 118 119 If an ancestor is found with a level other than NOTSET, then that ancestor's 120 level is treated as the effective level of the logger where the ancestor search 121 began, and is used to determine how a logging event is handled. 122 123 If the root is reached, and it has a level of NOTSET, then all messages will be 124 processed. Otherwise, the root's level will be used as the effective level. 125 126 See :ref:`levels` for a list of levels. 127 128 .. versionchanged:: 3.2 129 The *level* parameter now accepts a string representation of the 130 level such as 'INFO' as an alternative to the integer constants 131 such as :const:`INFO`. Note, however, that levels are internally stored 132 as integers, and methods such as e.g. :meth:`getEffectiveLevel` and 133 :meth:`isEnabledFor` will return/expect to be passed integers. 134 135 136 .. method:: Logger.isEnabledFor(level) 137 138 Indicates if a message of severity *level* would be processed by this logger. 139 This method checks first the module-level level set by 140 ``logging.disable(level)`` and then the logger's effective level as determined 141 by :meth:`getEffectiveLevel`. 142 143 144 .. method:: Logger.getEffectiveLevel() 145 146 Indicates the effective level for this logger. If a value other than 147 :const:`NOTSET` has been set using :meth:`setLevel`, it is returned. Otherwise, 148 the hierarchy is traversed towards the root until a value other than 149 :const:`NOTSET` is found, and that value is returned. The value returned is 150 an integer, typically one of :const:`logging.DEBUG`, :const:`logging.INFO` 151 etc. 152 153 154 .. method:: Logger.getChild(suffix) 155 156 Returns a logger which is a descendant to this logger, as determined by the suffix. 157 Thus, ``logging.getLogger('abc').getChild('def.ghi')`` would return the same 158 logger as would be returned by ``logging.getLogger('abc.def.ghi')``. This is a 159 convenience method, useful when the parent logger is named using e.g. ``__name__`` 160 rather than a literal string. 161 162 .. versionadded:: 3.2 163 164 165 .. method:: Logger.debug(msg, *args, **kwargs) 166 167 Logs a message with level :const:`DEBUG` on this logger. The *msg* is the 168 message format string, and the *args* are the arguments which are merged into 169 *msg* using the string formatting operator. (Note that this means that you can 170 use keywords in the format string, together with a single dictionary argument.) 171 No % formatting operation is performed on *msg* when no *args* are supplied. 172 173 There are four keyword arguments in *kwargs* which are inspected: 174 *exc_info*, *stack_info*, *stacklevel* and *extra*. 175 176 If *exc_info* does not evaluate as false, it causes exception information to be 177 added to the logging message. If an exception tuple (in the format returned by 178 :func:`sys.exc_info`) or an exception instance is provided, it is used; 179 otherwise, :func:`sys.exc_info` is called to get the exception information. 180 181 The second optional keyword argument is *stack_info*, which defaults to 182 ``False``. If true, stack information is added to the logging 183 message, including the actual logging call. Note that this is not the same 184 stack information as that displayed through specifying *exc_info*: The 185 former is stack frames from the bottom of the stack up to the logging call 186 in the current thread, whereas the latter is information about stack frames 187 which have been unwound, following an exception, while searching for 188 exception handlers. 189 190 You can specify *stack_info* independently of *exc_info*, e.g. to just show 191 how you got to a certain point in your code, even when no exceptions were 192 raised. The stack frames are printed following a header line which says: 193 194 .. code-block:: none 195 196 Stack (most recent call last): 197 198 This mimics the ``Traceback (most recent call last):`` which is used when 199 displaying exception frames. 200 201 The third optional keyword argument is *stacklevel*, which defaults to ``1``. 202 If greater than 1, the corresponding number of stack frames are skipped 203 when computing the line number and function name set in the :class:`LogRecord` 204 created for the logging event. This can be used in logging helpers so that 205 the function name, filename and line number recorded are not the information 206 for the helper function/method, but rather its caller. The name of this 207 parameter mirrors the equivalent one in the :mod:`warnings` module. 208 209 The fourth keyword argument is *extra* which can be used to pass a 210 dictionary which is used to populate the __dict__ of the :class:`LogRecord` 211 created for the logging event with user-defined attributes. These custom 212 attributes can then be used as you like. For example, they could be 213 incorporated into logged messages. For example:: 214 215 FORMAT = '%(asctime)s %(clientip)-15s %(user)-8s %(message)s' 216 logging.basicConfig(format=FORMAT) 217 d = {'clientip': '192.168.0.1', 'user': 'fbloggs'} 218 logger = logging.getLogger('tcpserver') 219 logger.warning('Protocol problem: %s', 'connection reset', extra=d) 220 221 would print something like 222 223 .. code-block:: none 224 225 2006-02-08 22:20:02,165 192.168.0.1 fbloggs Protocol problem: connection reset 226 227 The keys in the dictionary passed in *extra* should not clash with the keys used 228 by the logging system. (See the :class:`Formatter` documentation for more 229 information on which keys are used by the logging system.) 230 231 If you choose to use these attributes in logged messages, you need to exercise 232 some care. In the above example, for instance, the :class:`Formatter` has been 233 set up with a format string which expects 'clientip' and 'user' in the attribute 234 dictionary of the :class:`LogRecord`. If these are missing, the message will 235 not be logged because a string formatting exception will occur. So in this case, 236 you always need to pass the *extra* dictionary with these keys. 237 238 While this might be annoying, this feature is intended for use in specialized 239 circumstances, such as multi-threaded servers where the same code executes in 240 many contexts, and interesting conditions which arise are dependent on this 241 context (such as remote client IP address and authenticated user name, in the 242 above example). In such circumstances, it is likely that specialized 243 :class:`Formatter`\ s would be used with particular :class:`Handler`\ s. 244 245 .. versionchanged:: 3.2 246 The *stack_info* parameter was added. 247 248 .. versionchanged:: 3.5 249 The *exc_info* parameter can now accept exception instances. 250 251 .. versionchanged:: 3.8 252 The *stacklevel* parameter was added. 253 254 255 .. method:: Logger.info(msg, *args, **kwargs) 256 257 Logs a message with level :const:`INFO` on this logger. The arguments are 258 interpreted as for :meth:`debug`. 259 260 261 .. method:: Logger.warning(msg, *args, **kwargs) 262 263 Logs a message with level :const:`WARNING` on this logger. The arguments are 264 interpreted as for :meth:`debug`. 265 266 .. note:: There is an obsolete method ``warn`` which is functionally 267 identical to ``warning``. As ``warn`` is deprecated, please do not use 268 it - use ``warning`` instead. 269 270 .. method:: Logger.error(msg, *args, **kwargs) 271 272 Logs a message with level :const:`ERROR` on this logger. The arguments are 273 interpreted as for :meth:`debug`. 274 275 276 .. method:: Logger.critical(msg, *args, **kwargs) 277 278 Logs a message with level :const:`CRITICAL` on this logger. The arguments are 279 interpreted as for :meth:`debug`. 280 281 282 .. method:: Logger.log(level, msg, *args, **kwargs) 283 284 Logs a message with integer level *level* on this logger. The other arguments are 285 interpreted as for :meth:`debug`. 286 287 288 .. method:: Logger.exception(msg, *args, **kwargs) 289 290 Logs a message with level :const:`ERROR` on this logger. The arguments are 291 interpreted as for :meth:`debug`. Exception info is added to the logging 292 message. This method should only be called from an exception handler. 293 294 295 .. method:: Logger.addFilter(filter) 296 297 Adds the specified filter *filter* to this logger. 298 299 300 .. method:: Logger.removeFilter(filter) 301 302 Removes the specified filter *filter* from this logger. 303 304 305 .. method:: Logger.filter(record) 306 307 Apply this logger's filters to the record and return ``True`` if the 308 record is to be processed. The filters are consulted in turn, until one of 309 them returns a false value. If none of them return a false value, the record 310 will be processed (passed to handlers). If one returns a false value, no 311 further processing of the record occurs. 312 313 314 .. method:: Logger.addHandler(hdlr) 315 316 Adds the specified handler *hdlr* to this logger. 317 318 319 .. method:: Logger.removeHandler(hdlr) 320 321 Removes the specified handler *hdlr* from this logger. 322 323 324 .. method:: Logger.findCaller(stack_info=False, stacklevel=1) 325 326 Finds the caller's source filename and line number. Returns the filename, line 327 number, function name and stack information as a 4-element tuple. The stack 328 information is returned as ``None`` unless *stack_info* is ``True``. 329 330 The *stacklevel* parameter is passed from code calling the :meth:`debug` 331 and other APIs. If greater than 1, the excess is used to skip stack frames 332 before determining the values to be returned. This will generally be useful 333 when calling logging APIs from helper/wrapper code, so that the information 334 in the event log refers not to the helper/wrapper code, but to the code that 335 calls it. 336 337 338 .. method:: Logger.handle(record) 339 340 Handles a record by passing it to all handlers associated with this logger and 341 its ancestors (until a false value of *propagate* is found). This method is used 342 for unpickled records received from a socket, as well as those created locally. 343 Logger-level filtering is applied using :meth:`~Logger.filter`. 344 345 346 .. method:: Logger.makeRecord(name, level, fn, lno, msg, args, exc_info, func=None, extra=None, sinfo=None) 347 348 This is a factory method which can be overridden in subclasses to create 349 specialized :class:`LogRecord` instances. 350 351 .. method:: Logger.hasHandlers() 352 353 Checks to see if this logger has any handlers configured. This is done by 354 looking for handlers in this logger and its parents in the logger hierarchy. 355 Returns ``True`` if a handler was found, else ``False``. The method stops searching 356 up the hierarchy whenever a logger with the 'propagate' attribute set to 357 false is found - that will be the last logger which is checked for the 358 existence of handlers. 359 360 .. versionadded:: 3.2 361 362 .. versionchanged:: 3.7 363 Loggers can now be pickled and unpickled. 364 365.. _levels: 366 367Logging Levels 368-------------- 369 370The numeric values of logging levels are given in the following table. These are 371primarily of interest if you want to define your own levels, and need them to 372have specific values relative to the predefined levels. If you define a level 373with the same numeric value, it overwrites the predefined value; the predefined 374name is lost. 375 376+--------------+---------------+ 377| Level | Numeric value | 378+==============+===============+ 379| ``CRITICAL`` | 50 | 380+--------------+---------------+ 381| ``ERROR`` | 40 | 382+--------------+---------------+ 383| ``WARNING`` | 30 | 384+--------------+---------------+ 385| ``INFO`` | 20 | 386+--------------+---------------+ 387| ``DEBUG`` | 10 | 388+--------------+---------------+ 389| ``NOTSET`` | 0 | 390+--------------+---------------+ 391 392 393.. _handler: 394 395Handler Objects 396--------------- 397 398Handlers have the following attributes and methods. Note that :class:`Handler` 399is never instantiated directly; this class acts as a base for more useful 400subclasses. However, the :meth:`__init__` method in subclasses needs to call 401:meth:`Handler.__init__`. 402 403.. class:: Handler 404 405 .. method:: Handler.__init__(level=NOTSET) 406 407 Initializes the :class:`Handler` instance by setting its level, setting the list 408 of filters to the empty list and creating a lock (using :meth:`createLock`) for 409 serializing access to an I/O mechanism. 410 411 412 .. method:: Handler.createLock() 413 414 Initializes a thread lock which can be used to serialize access to underlying 415 I/O functionality which may not be threadsafe. 416 417 418 .. method:: Handler.acquire() 419 420 Acquires the thread lock created with :meth:`createLock`. 421 422 423 .. method:: Handler.release() 424 425 Releases the thread lock acquired with :meth:`acquire`. 426 427 428 .. method:: Handler.setLevel(level) 429 430 Sets the threshold for this handler to *level*. Logging messages which are 431 less severe than *level* will be ignored. When a handler is created, the 432 level is set to :const:`NOTSET` (which causes all messages to be 433 processed). 434 435 See :ref:`levels` for a list of levels. 436 437 .. versionchanged:: 3.2 438 The *level* parameter now accepts a string representation of the 439 level such as 'INFO' as an alternative to the integer constants 440 such as :const:`INFO`. 441 442 443 .. method:: Handler.setFormatter(fmt) 444 445 Sets the :class:`Formatter` for this handler to *fmt*. 446 447 448 .. method:: Handler.addFilter(filter) 449 450 Adds the specified filter *filter* to this handler. 451 452 453 .. method:: Handler.removeFilter(filter) 454 455 Removes the specified filter *filter* from this handler. 456 457 458 .. method:: Handler.filter(record) 459 460 Apply this handler's filters to the record and return ``True`` if the 461 record is to be processed. The filters are consulted in turn, until one of 462 them returns a false value. If none of them return a false value, the record 463 will be emitted. If one returns a false value, the handler will not emit the 464 record. 465 466 467 .. method:: Handler.flush() 468 469 Ensure all logging output has been flushed. This version does nothing and is 470 intended to be implemented by subclasses. 471 472 473 .. method:: Handler.close() 474 475 Tidy up any resources used by the handler. This version does no output but 476 removes the handler from an internal list of handlers which is closed when 477 :func:`shutdown` is called. Subclasses should ensure that this gets called 478 from overridden :meth:`close` methods. 479 480 481 .. method:: Handler.handle(record) 482 483 Conditionally emits the specified logging record, depending on filters which may 484 have been added to the handler. Wraps the actual emission of the record with 485 acquisition/release of the I/O thread lock. 486 487 488 .. method:: Handler.handleError(record) 489 490 This method should be called from handlers when an exception is encountered 491 during an :meth:`emit` call. If the module-level attribute 492 ``raiseExceptions`` is ``False``, exceptions get silently ignored. This is 493 what is mostly wanted for a logging system - most users will not care about 494 errors in the logging system, they are more interested in application 495 errors. You could, however, replace this with a custom handler if you wish. 496 The specified record is the one which was being processed when the exception 497 occurred. (The default value of ``raiseExceptions`` is ``True``, as that is 498 more useful during development). 499 500 501 .. method:: Handler.format(record) 502 503 Do formatting for a record - if a formatter is set, use it. Otherwise, use the 504 default formatter for the module. 505 506 507 .. method:: Handler.emit(record) 508 509 Do whatever it takes to actually log the specified logging record. This version 510 is intended to be implemented by subclasses and so raises a 511 :exc:`NotImplementedError`. 512 513For a list of handlers included as standard, see :mod:`logging.handlers`. 514 515.. _formatter-objects: 516 517Formatter Objects 518----------------- 519 520.. currentmodule:: logging 521 522:class:`Formatter` objects have the following attributes and methods. They are 523responsible for converting a :class:`LogRecord` to (usually) a string which can 524be interpreted by either a human or an external system. The base 525:class:`Formatter` allows a formatting string to be specified. If none is 526supplied, the default value of ``'%(message)s'`` is used, which just includes 527the message in the logging call. To have additional items of information in the 528formatted output (such as a timestamp), keep reading. 529 530A Formatter can be initialized with a format string which makes use of knowledge 531of the :class:`LogRecord` attributes - such as the default value mentioned above 532making use of the fact that the user's message and arguments are pre-formatted 533into a :class:`LogRecord`'s *message* attribute. This format string contains 534standard Python %-style mapping keys. See section :ref:`old-string-formatting` 535for more information on string formatting. 536 537The useful mapping keys in a :class:`LogRecord` are given in the section on 538:ref:`logrecord-attributes`. 539 540 541.. class:: Formatter(fmt=None, datefmt=None, style='%', validate=True, *, defaults=None) 542 543 Returns a new instance of the :class:`Formatter` class. The instance is 544 initialized with a format string for the message as a whole, as well as a 545 format string for the date/time portion of a message. If no *fmt* is 546 specified, ``'%(message)s'`` is used. If no *datefmt* is specified, a format 547 is used which is described in the :meth:`formatTime` documentation. 548 549 The *style* parameter can be one of '%', '{' or '$' and determines how 550 the format string will be merged with its data: using one of %-formatting, 551 :meth:`str.format` or :class:`string.Template`. This only applies to the 552 format string *fmt* (e.g. ``'%(message)s'`` or ``{message}``), not to the 553 actual log messages passed to ``Logger.debug`` etc; see 554 :ref:`formatting-styles` for more information on using {- and $-formatting 555 for log messages. 556 557 The *defaults* parameter can be a dictionary with default values to use in 558 custom fields. For example: 559 ``logging.Formatter('%(ip)s %(message)s', defaults={"ip": None})`` 560 561 .. versionchanged:: 3.2 562 The *style* parameter was added. 563 564 .. versionchanged:: 3.8 565 The *validate* parameter was added. Incorrect or mismatched style and fmt 566 will raise a ``ValueError``. 567 For example: ``logging.Formatter('%(asctime)s - %(message)s', style='{')``. 568 569 .. versionchanged:: 3.10 570 The *defaults* parameter was added. 571 572 .. method:: format(record) 573 574 The record's attribute dictionary is used as the operand to a string 575 formatting operation. Returns the resulting string. Before formatting the 576 dictionary, a couple of preparatory steps are carried out. The *message* 577 attribute of the record is computed using *msg* % *args*. If the 578 formatting string contains ``'(asctime)'``, :meth:`formatTime` is called 579 to format the event time. If there is exception information, it is 580 formatted using :meth:`formatException` and appended to the message. Note 581 that the formatted exception information is cached in attribute 582 *exc_text*. This is useful because the exception information can be 583 pickled and sent across the wire, but you should be careful if you have 584 more than one :class:`Formatter` subclass which customizes the formatting 585 of exception information. In this case, you will have to clear the cached 586 value (by setting the *exc_text* attribute to ``None``) after a formatter 587 has done its formatting, so that the next formatter to handle the event 588 doesn't use the cached value, but recalculates it afresh. 589 590 If stack information is available, it's appended after the exception 591 information, using :meth:`formatStack` to transform it if necessary. 592 593 594 .. method:: formatTime(record, datefmt=None) 595 596 This method should be called from :meth:`format` by a formatter which 597 wants to make use of a formatted time. This method can be overridden in 598 formatters to provide for any specific requirement, but the basic behavior 599 is as follows: if *datefmt* (a string) is specified, it is used with 600 :func:`time.strftime` to format the creation time of the 601 record. Otherwise, the format '%Y-%m-%d %H:%M:%S,uuu' is used, where the 602 uuu part is a millisecond value and the other letters are as per the 603 :func:`time.strftime` documentation. An example time in this format is 604 ``2003-01-23 00:29:50,411``. The resulting string is returned. 605 606 This function uses a user-configurable function to convert the creation 607 time to a tuple. By default, :func:`time.localtime` is used; to change 608 this for a particular formatter instance, set the ``converter`` attribute 609 to a function with the same signature as :func:`time.localtime` or 610 :func:`time.gmtime`. To change it for all formatters, for example if you 611 want all logging times to be shown in GMT, set the ``converter`` 612 attribute in the ``Formatter`` class. 613 614 .. versionchanged:: 3.3 615 Previously, the default format was hard-coded as in this example: 616 ``2010-09-06 22:38:15,292`` where the part before the comma is 617 handled by a strptime format string (``'%Y-%m-%d %H:%M:%S'``), and the 618 part after the comma is a millisecond value. Because strptime does not 619 have a format placeholder for milliseconds, the millisecond value is 620 appended using another format string, ``'%s,%03d'`` --- and both of these 621 format strings have been hardcoded into this method. With the change, 622 these strings are defined as class-level attributes which can be 623 overridden at the instance level when desired. The names of the 624 attributes are ``default_time_format`` (for the strptime format string) 625 and ``default_msec_format`` (for appending the millisecond value). 626 627 .. versionchanged:: 3.9 628 The ``default_msec_format`` can be ``None``. 629 630 .. method:: formatException(exc_info) 631 632 Formats the specified exception information (a standard exception tuple as 633 returned by :func:`sys.exc_info`) as a string. This default implementation 634 just uses :func:`traceback.print_exception`. The resulting string is 635 returned. 636 637 .. method:: formatStack(stack_info) 638 639 Formats the specified stack information (a string as returned by 640 :func:`traceback.print_stack`, but with the last newline removed) as a 641 string. This default implementation just returns the input value. 642 643.. _filter: 644 645Filter Objects 646-------------- 647 648``Filters`` can be used by ``Handlers`` and ``Loggers`` for more sophisticated 649filtering than is provided by levels. The base filter class only allows events 650which are below a certain point in the logger hierarchy. For example, a filter 651initialized with 'A.B' will allow events logged by loggers 'A.B', 'A.B.C', 652'A.B.C.D', 'A.B.D' etc. but not 'A.BB', 'B.A.B' etc. If initialized with the 653empty string, all events are passed. 654 655 656.. class:: Filter(name='') 657 658 Returns an instance of the :class:`Filter` class. If *name* is specified, it 659 names a logger which, together with its children, will have its events allowed 660 through the filter. If *name* is the empty string, allows every event. 661 662 663 .. method:: filter(record) 664 665 Is the specified record to be logged? Returns zero for no, nonzero for 666 yes. If deemed appropriate, the record may be modified in-place by this 667 method. 668 669Note that filters attached to handlers are consulted before an event is 670emitted by the handler, whereas filters attached to loggers are consulted 671whenever an event is logged (using :meth:`debug`, :meth:`info`, 672etc.), before sending an event to handlers. This means that events which have 673been generated by descendant loggers will not be filtered by a logger's filter 674setting, unless the filter has also been applied to those descendant loggers. 675 676You don't actually need to subclass ``Filter``: you can pass any instance 677which has a ``filter`` method with the same semantics. 678 679.. versionchanged:: 3.2 680 You don't need to create specialized ``Filter`` classes, or use other 681 classes with a ``filter`` method: you can use a function (or other 682 callable) as a filter. The filtering logic will check to see if the filter 683 object has a ``filter`` attribute: if it does, it's assumed to be a 684 ``Filter`` and its :meth:`~Filter.filter` method is called. Otherwise, it's 685 assumed to be a callable and called with the record as the single 686 parameter. The returned value should conform to that returned by 687 :meth:`~Filter.filter`. 688 689Although filters are used primarily to filter records based on more 690sophisticated criteria than levels, they get to see every record which is 691processed by the handler or logger they're attached to: this can be useful if 692you want to do things like counting how many records were processed by a 693particular logger or handler, or adding, changing or removing attributes in 694the :class:`LogRecord` being processed. Obviously changing the LogRecord needs 695to be done with some care, but it does allow the injection of contextual 696information into logs (see :ref:`filters-contextual`). 697 698.. _log-record: 699 700LogRecord Objects 701----------------- 702 703:class:`LogRecord` instances are created automatically by the :class:`Logger` 704every time something is logged, and can be created manually via 705:func:`makeLogRecord` (for example, from a pickled event received over the 706wire). 707 708 709.. class:: LogRecord(name, level, pathname, lineno, msg, args, exc_info, func=None, sinfo=None) 710 711 Contains all the information pertinent to the event being logged. 712 713 The primary information is passed in :attr:`msg` and :attr:`args`, which 714 are combined using ``msg % args`` to create the :attr:`message` field of the 715 record. 716 717 :param name: The name of the logger used to log the event represented by 718 this LogRecord. Note that this name will always have this 719 value, even though it may be emitted by a handler attached to 720 a different (ancestor) logger. 721 :param level: The numeric level of the logging event (one of DEBUG, INFO etc.) 722 Note that this is converted to *two* attributes of the LogRecord: 723 ``levelno`` for the numeric value and ``levelname`` for the 724 corresponding level name. 725 :param pathname: The full pathname of the source file where the logging call 726 was made. 727 :param lineno: The line number in the source file where the logging call was 728 made. 729 :param msg: The event description message, possibly a format string with 730 placeholders for variable data. 731 :param args: Variable data to merge into the *msg* argument to obtain the 732 event description. 733 :param exc_info: An exception tuple with the current exception information, 734 or ``None`` if no exception information is available. 735 :param func: The name of the function or method from which the logging call 736 was invoked. 737 :param sinfo: A text string representing stack information from the base of 738 the stack in the current thread, up to the logging call. 739 740 .. method:: getMessage() 741 742 Returns the message for this :class:`LogRecord` instance after merging any 743 user-supplied arguments with the message. If the user-supplied message 744 argument to the logging call is not a string, :func:`str` is called on it to 745 convert it to a string. This allows use of user-defined classes as 746 messages, whose ``__str__`` method can return the actual format string to 747 be used. 748 749 .. versionchanged:: 3.2 750 The creation of a :class:`LogRecord` has been made more configurable by 751 providing a factory which is used to create the record. The factory can be 752 set using :func:`getLogRecordFactory` and :func:`setLogRecordFactory` 753 (see this for the factory's signature). 754 755 This functionality can be used to inject your own values into a 756 :class:`LogRecord` at creation time. You can use the following pattern:: 757 758 old_factory = logging.getLogRecordFactory() 759 760 def record_factory(*args, **kwargs): 761 record = old_factory(*args, **kwargs) 762 record.custom_attribute = 0xdecafbad 763 return record 764 765 logging.setLogRecordFactory(record_factory) 766 767 With this pattern, multiple factories could be chained, and as long 768 as they don't overwrite each other's attributes or unintentionally 769 overwrite the standard attributes listed above, there should be no 770 surprises. 771 772 773.. _logrecord-attributes: 774 775LogRecord attributes 776-------------------- 777 778The LogRecord has a number of attributes, most of which are derived from the 779parameters to the constructor. (Note that the names do not always correspond 780exactly between the LogRecord constructor parameters and the LogRecord 781attributes.) These attributes can be used to merge data from the record into 782the format string. The following table lists (in alphabetical order) the 783attribute names, their meanings and the corresponding placeholder in a %-style 784format string. 785 786If you are using {}-formatting (:func:`str.format`), you can use 787``{attrname}`` as the placeholder in the format string. If you are using 788$-formatting (:class:`string.Template`), use the form ``${attrname}``. In 789both cases, of course, replace ``attrname`` with the actual attribute name 790you want to use. 791 792In the case of {}-formatting, you can specify formatting flags by placing them 793after the attribute name, separated from it with a colon. For example: a 794placeholder of ``{msecs:03d}`` would format a millisecond value of ``4`` as 795``004``. Refer to the :meth:`str.format` documentation for full details on 796the options available to you. 797 798+----------------+-------------------------+-----------------------------------------------+ 799| Attribute name | Format | Description | 800+================+=========================+===============================================+ 801| args | You shouldn't need to | The tuple of arguments merged into ``msg`` to | 802| | format this yourself. | produce ``message``, or a dict whose values | 803| | | are used for the merge (when there is only one| 804| | | argument, and it is a dictionary). | 805+----------------+-------------------------+-----------------------------------------------+ 806| asctime | ``%(asctime)s`` | Human-readable time when the | 807| | | :class:`LogRecord` was created. By default | 808| | | this is of the form '2003-07-08 16:49:45,896' | 809| | | (the numbers after the comma are millisecond | 810| | | portion of the time). | 811+----------------+-------------------------+-----------------------------------------------+ 812| created | ``%(created)f`` | Time when the :class:`LogRecord` was created | 813| | | (as returned by :func:`time.time`). | 814+----------------+-------------------------+-----------------------------------------------+ 815| exc_info | You shouldn't need to | Exception tuple (à la ``sys.exc_info``) or, | 816| | format this yourself. | if no exception has occurred, ``None``. | 817+----------------+-------------------------+-----------------------------------------------+ 818| filename | ``%(filename)s`` | Filename portion of ``pathname``. | 819+----------------+-------------------------+-----------------------------------------------+ 820| funcName | ``%(funcName)s`` | Name of function containing the logging call. | 821+----------------+-------------------------+-----------------------------------------------+ 822| levelname | ``%(levelname)s`` | Text logging level for the message | 823| | | (``'DEBUG'``, ``'INFO'``, ``'WARNING'``, | 824| | | ``'ERROR'``, ``'CRITICAL'``). | 825+----------------+-------------------------+-----------------------------------------------+ 826| levelno | ``%(levelno)s`` | Numeric logging level for the message | 827| | | (:const:`DEBUG`, :const:`INFO`, | 828| | | :const:`WARNING`, :const:`ERROR`, | 829| | | :const:`CRITICAL`). | 830+----------------+-------------------------+-----------------------------------------------+ 831| lineno | ``%(lineno)d`` | Source line number where the logging call was | 832| | | issued (if available). | 833+----------------+-------------------------+-----------------------------------------------+ 834| message | ``%(message)s`` | The logged message, computed as ``msg % | 835| | | args``. This is set when | 836| | | :meth:`Formatter.format` is invoked. | 837+----------------+-------------------------+-----------------------------------------------+ 838| module | ``%(module)s`` | Module (name portion of ``filename``). | 839+----------------+-------------------------+-----------------------------------------------+ 840| msecs | ``%(msecs)d`` | Millisecond portion of the time when the | 841| | | :class:`LogRecord` was created. | 842+----------------+-------------------------+-----------------------------------------------+ 843| msg | You shouldn't need to | The format string passed in the original | 844| | format this yourself. | logging call. Merged with ``args`` to | 845| | | produce ``message``, or an arbitrary object | 846| | | (see :ref:`arbitrary-object-messages`). | 847+----------------+-------------------------+-----------------------------------------------+ 848| name | ``%(name)s`` | Name of the logger used to log the call. | 849+----------------+-------------------------+-----------------------------------------------+ 850| pathname | ``%(pathname)s`` | Full pathname of the source file where the | 851| | | logging call was issued (if available). | 852+----------------+-------------------------+-----------------------------------------------+ 853| process | ``%(process)d`` | Process ID (if available). | 854+----------------+-------------------------+-----------------------------------------------+ 855| processName | ``%(processName)s`` | Process name (if available). | 856+----------------+-------------------------+-----------------------------------------------+ 857| relativeCreated| ``%(relativeCreated)d`` | Time in milliseconds when the LogRecord was | 858| | | created, relative to the time the logging | 859| | | module was loaded. | 860+----------------+-------------------------+-----------------------------------------------+ 861| stack_info | You shouldn't need to | Stack frame information (where available) | 862| | format this yourself. | from the bottom of the stack in the current | 863| | | thread, up to and including the stack frame | 864| | | of the logging call which resulted in the | 865| | | creation of this record. | 866+----------------+-------------------------+-----------------------------------------------+ 867| thread | ``%(thread)d`` | Thread ID (if available). | 868+----------------+-------------------------+-----------------------------------------------+ 869| threadName | ``%(threadName)s`` | Thread name (if available). | 870+----------------+-------------------------+-----------------------------------------------+ 871 872.. versionchanged:: 3.1 873 *processName* was added. 874 875 876.. _logger-adapter: 877 878LoggerAdapter Objects 879--------------------- 880 881:class:`LoggerAdapter` instances are used to conveniently pass contextual 882information into logging calls. For a usage example, see the section on 883:ref:`adding contextual information to your logging output <context-info>`. 884 885.. class:: LoggerAdapter(logger, extra) 886 887 Returns an instance of :class:`LoggerAdapter` initialized with an 888 underlying :class:`Logger` instance and a dict-like object. 889 890 .. method:: process(msg, kwargs) 891 892 Modifies the message and/or keyword arguments passed to a logging call in 893 order to insert contextual information. This implementation takes the object 894 passed as *extra* to the constructor and adds it to *kwargs* using key 895 'extra'. The return value is a (*msg*, *kwargs*) tuple which has the 896 (possibly modified) versions of the arguments passed in. 897 898In addition to the above, :class:`LoggerAdapter` supports the following 899methods of :class:`Logger`: :meth:`~Logger.debug`, :meth:`~Logger.info`, 900:meth:`~Logger.warning`, :meth:`~Logger.error`, :meth:`~Logger.exception`, 901:meth:`~Logger.critical`, :meth:`~Logger.log`, :meth:`~Logger.isEnabledFor`, 902:meth:`~Logger.getEffectiveLevel`, :meth:`~Logger.setLevel` and 903:meth:`~Logger.hasHandlers`. These methods have the same signatures as their 904counterparts in :class:`Logger`, so you can use the two types of instances 905interchangeably. 906 907.. versionchanged:: 3.2 908 The :meth:`~Logger.isEnabledFor`, :meth:`~Logger.getEffectiveLevel`, 909 :meth:`~Logger.setLevel` and :meth:`~Logger.hasHandlers` methods were added 910 to :class:`LoggerAdapter`. These methods delegate to the underlying logger. 911 912.. versionchanged:: 3.6 913 Attribute :attr:`manager` and method :meth:`_log` were added, which 914 delegate to the underlying logger and allow adapters to be nested. 915 916 917Thread Safety 918------------- 919 920The logging module is intended to be thread-safe without any special work 921needing to be done by its clients. It achieves this though using threading 922locks; there is one lock to serialize access to the module's shared data, and 923each handler also creates a lock to serialize access to its underlying I/O. 924 925If you are implementing asynchronous signal handlers using the :mod:`signal` 926module, you may not be able to use logging from within such handlers. This is 927because lock implementations in the :mod:`threading` module are not always 928re-entrant, and so cannot be invoked from such signal handlers. 929 930 931Module-Level Functions 932---------------------- 933 934In addition to the classes described above, there are a number of module-level 935functions. 936 937 938.. function:: getLogger(name=None) 939 940 Return a logger with the specified name or, if name is ``None``, return a 941 logger which is the root logger of the hierarchy. If specified, the name is 942 typically a dot-separated hierarchical name like *'a'*, *'a.b'* or *'a.b.c.d'*. 943 Choice of these names is entirely up to the developer who is using logging. 944 945 All calls to this function with a given name return the same logger instance. 946 This means that logger instances never need to be passed between different parts 947 of an application. 948 949 950.. function:: getLoggerClass() 951 952 Return either the standard :class:`Logger` class, or the last class passed to 953 :func:`setLoggerClass`. This function may be called from within a new class 954 definition, to ensure that installing a customized :class:`Logger` class will 955 not undo customizations already applied by other code. For example:: 956 957 class MyLogger(logging.getLoggerClass()): 958 # ... override behaviour here 959 960 961.. function:: getLogRecordFactory() 962 963 Return a callable which is used to create a :class:`LogRecord`. 964 965 .. versionadded:: 3.2 966 This function has been provided, along with :func:`setLogRecordFactory`, 967 to allow developers more control over how the :class:`LogRecord` 968 representing a logging event is constructed. 969 970 See :func:`setLogRecordFactory` for more information about the how the 971 factory is called. 972 973.. function:: debug(msg, *args, **kwargs) 974 975 Logs a message with level :const:`DEBUG` on the root logger. The *msg* is the 976 message format string, and the *args* are the arguments which are merged into 977 *msg* using the string formatting operator. (Note that this means that you can 978 use keywords in the format string, together with a single dictionary argument.) 979 980 There are three keyword arguments in *kwargs* which are inspected: *exc_info* 981 which, if it does not evaluate as false, causes exception information to be 982 added to the logging message. If an exception tuple (in the format returned by 983 :func:`sys.exc_info`) or an exception instance is provided, it is used; 984 otherwise, :func:`sys.exc_info` is called to get the exception information. 985 986 The second optional keyword argument is *stack_info*, which defaults to 987 ``False``. If true, stack information is added to the logging 988 message, including the actual logging call. Note that this is not the same 989 stack information as that displayed through specifying *exc_info*: The 990 former is stack frames from the bottom of the stack up to the logging call 991 in the current thread, whereas the latter is information about stack frames 992 which have been unwound, following an exception, while searching for 993 exception handlers. 994 995 You can specify *stack_info* independently of *exc_info*, e.g. to just show 996 how you got to a certain point in your code, even when no exceptions were 997 raised. The stack frames are printed following a header line which says: 998 999 .. code-block:: none 1000 1001 Stack (most recent call last): 1002 1003 This mimics the ``Traceback (most recent call last):`` which is used when 1004 displaying exception frames. 1005 1006 The third optional keyword argument is *extra* which can be used to pass a 1007 dictionary which is used to populate the __dict__ of the LogRecord created for 1008 the logging event with user-defined attributes. These custom attributes can then 1009 be used as you like. For example, they could be incorporated into logged 1010 messages. For example:: 1011 1012 FORMAT = '%(asctime)s %(clientip)-15s %(user)-8s %(message)s' 1013 logging.basicConfig(format=FORMAT) 1014 d = {'clientip': '192.168.0.1', 'user': 'fbloggs'} 1015 logging.warning('Protocol problem: %s', 'connection reset', extra=d) 1016 1017 would print something like: 1018 1019 .. code-block:: none 1020 1021 2006-02-08 22:20:02,165 192.168.0.1 fbloggs Protocol problem: connection reset 1022 1023 The keys in the dictionary passed in *extra* should not clash with the keys used 1024 by the logging system. (See the :class:`Formatter` documentation for more 1025 information on which keys are used by the logging system.) 1026 1027 If you choose to use these attributes in logged messages, you need to exercise 1028 some care. In the above example, for instance, the :class:`Formatter` has been 1029 set up with a format string which expects 'clientip' and 'user' in the attribute 1030 dictionary of the LogRecord. If these are missing, the message will not be 1031 logged because a string formatting exception will occur. So in this case, you 1032 always need to pass the *extra* dictionary with these keys. 1033 1034 While this might be annoying, this feature is intended for use in specialized 1035 circumstances, such as multi-threaded servers where the same code executes in 1036 many contexts, and interesting conditions which arise are dependent on this 1037 context (such as remote client IP address and authenticated user name, in the 1038 above example). In such circumstances, it is likely that specialized 1039 :class:`Formatter`\ s would be used with particular :class:`Handler`\ s. 1040 1041 .. versionchanged:: 3.2 1042 The *stack_info* parameter was added. 1043 1044.. function:: info(msg, *args, **kwargs) 1045 1046 Logs a message with level :const:`INFO` on the root logger. The arguments are 1047 interpreted as for :func:`debug`. 1048 1049 1050.. function:: warning(msg, *args, **kwargs) 1051 1052 Logs a message with level :const:`WARNING` on the root logger. The arguments 1053 are interpreted as for :func:`debug`. 1054 1055 .. note:: There is an obsolete function ``warn`` which is functionally 1056 identical to ``warning``. As ``warn`` is deprecated, please do not use 1057 it - use ``warning`` instead. 1058 1059 1060.. function:: error(msg, *args, **kwargs) 1061 1062 Logs a message with level :const:`ERROR` on the root logger. The arguments are 1063 interpreted as for :func:`debug`. 1064 1065 1066.. function:: critical(msg, *args, **kwargs) 1067 1068 Logs a message with level :const:`CRITICAL` on the root logger. The arguments 1069 are interpreted as for :func:`debug`. 1070 1071 1072.. function:: exception(msg, *args, **kwargs) 1073 1074 Logs a message with level :const:`ERROR` on the root logger. The arguments are 1075 interpreted as for :func:`debug`. Exception info is added to the logging 1076 message. This function should only be called from an exception handler. 1077 1078.. function:: log(level, msg, *args, **kwargs) 1079 1080 Logs a message with level *level* on the root logger. The other arguments are 1081 interpreted as for :func:`debug`. 1082 1083 .. note:: The above module-level convenience functions, which delegate to the 1084 root logger, call :func:`basicConfig` to ensure that at least one handler 1085 is available. Because of this, they should *not* be used in threads, 1086 in versions of Python earlier than 2.7.1 and 3.2, unless at least one 1087 handler has been added to the root logger *before* the threads are 1088 started. In earlier versions of Python, due to a thread safety shortcoming 1089 in :func:`basicConfig`, this can (under rare circumstances) lead to 1090 handlers being added multiple times to the root logger, which can in turn 1091 lead to multiple messages for the same event. 1092 1093.. function:: disable(level=CRITICAL) 1094 1095 Provides an overriding level *level* for all loggers which takes precedence over 1096 the logger's own level. When the need arises to temporarily throttle logging 1097 output down across the whole application, this function can be useful. Its 1098 effect is to disable all logging calls of severity *level* and below, so that 1099 if you call it with a value of INFO, then all INFO and DEBUG events would be 1100 discarded, whereas those of severity WARNING and above would be processed 1101 according to the logger's effective level. If 1102 ``logging.disable(logging.NOTSET)`` is called, it effectively removes this 1103 overriding level, so that logging output again depends on the effective 1104 levels of individual loggers. 1105 1106 Note that if you have defined any custom logging level higher than 1107 ``CRITICAL`` (this is not recommended), you won't be able to rely on the 1108 default value for the *level* parameter, but will have to explicitly supply a 1109 suitable value. 1110 1111 .. versionchanged:: 3.7 1112 The *level* parameter was defaulted to level ``CRITICAL``. See 1113 :issue:`28524` for more information about this change. 1114 1115.. function:: addLevelName(level, levelName) 1116 1117 Associates level *level* with text *levelName* in an internal dictionary, which is 1118 used to map numeric levels to a textual representation, for example when a 1119 :class:`Formatter` formats a message. This function can also be used to define 1120 your own levels. The only constraints are that all levels used must be 1121 registered using this function, levels should be positive integers and they 1122 should increase in increasing order of severity. 1123 1124 .. note:: If you are thinking of defining your own levels, please see the 1125 section on :ref:`custom-levels`. 1126 1127.. function:: getLevelName(level) 1128 1129 Returns the textual or numeric representation of logging level *level*. 1130 1131 If *level* is one of the predefined levels :const:`CRITICAL`, :const:`ERROR`, 1132 :const:`WARNING`, :const:`INFO` or :const:`DEBUG` then you get the 1133 corresponding string. If you have associated levels with names using 1134 :func:`addLevelName` then the name you have associated with *level* is 1135 returned. If a numeric value corresponding to one of the defined levels is 1136 passed in, the corresponding string representation is returned. 1137 1138 The *level* parameter also accepts a string representation of the level such 1139 as 'INFO'. In such cases, this functions returns the corresponding numeric 1140 value of the level. 1141 1142 If no matching numeric or string value is passed in, the string 1143 'Level %s' % level is returned. 1144 1145 .. note:: Levels are internally integers (as they need to be compared in the 1146 logging logic). This function is used to convert between an integer level 1147 and the level name displayed in the formatted log output by means of the 1148 ``%(levelname)s`` format specifier (see :ref:`logrecord-attributes`), and 1149 vice versa. 1150 1151 .. versionchanged:: 3.4 1152 In Python versions earlier than 3.4, this function could also be passed a 1153 text level, and would return the corresponding numeric value of the level. 1154 This undocumented behaviour was considered a mistake, and was removed in 1155 Python 3.4, but reinstated in 3.4.2 due to retain backward compatibility. 1156 1157.. function:: makeLogRecord(attrdict) 1158 1159 Creates and returns a new :class:`LogRecord` instance whose attributes are 1160 defined by *attrdict*. This function is useful for taking a pickled 1161 :class:`LogRecord` attribute dictionary, sent over a socket, and reconstituting 1162 it as a :class:`LogRecord` instance at the receiving end. 1163 1164 1165.. function:: basicConfig(**kwargs) 1166 1167 Does basic configuration for the logging system by creating a 1168 :class:`StreamHandler` with a default :class:`Formatter` and adding it to the 1169 root logger. The functions :func:`debug`, :func:`info`, :func:`warning`, 1170 :func:`error` and :func:`critical` will call :func:`basicConfig` automatically 1171 if no handlers are defined for the root logger. 1172 1173 This function does nothing if the root logger already has handlers 1174 configured, unless the keyword argument *force* is set to ``True``. 1175 1176 .. note:: This function should be called from the main thread 1177 before other threads are started. In versions of Python prior to 1178 2.7.1 and 3.2, if this function is called from multiple threads, 1179 it is possible (in rare circumstances) that a handler will be added 1180 to the root logger more than once, leading to unexpected results 1181 such as messages being duplicated in the log. 1182 1183 The following keyword arguments are supported. 1184 1185 .. tabularcolumns:: |l|L| 1186 1187 +--------------+---------------------------------------------+ 1188 | Format | Description | 1189 +==============+=============================================+ 1190 | *filename* | Specifies that a :class:`FileHandler` be | 1191 | | created, using the specified filename, | 1192 | | rather than a :class:`StreamHandler`. | 1193 +--------------+---------------------------------------------+ 1194 | *filemode* | If *filename* is specified, open the file | 1195 | | in this :ref:`mode <filemodes>`. Defaults | 1196 | | to ``'a'``. | 1197 +--------------+---------------------------------------------+ 1198 | *format* | Use the specified format string for the | 1199 | | handler. Defaults to attributes | 1200 | | ``levelname``, ``name`` and ``message`` | 1201 | | separated by colons. | 1202 +--------------+---------------------------------------------+ 1203 | *datefmt* | Use the specified date/time format, as | 1204 | | accepted by :func:`time.strftime`. | 1205 +--------------+---------------------------------------------+ 1206 | *style* | If *format* is specified, use this style | 1207 | | for the format string. One of ``'%'``, | 1208 | | ``'{'`` or ``'$'`` for :ref:`printf-style | 1209 | | <old-string-formatting>`, | 1210 | | :meth:`str.format` or | 1211 | | :class:`string.Template` respectively. | 1212 | | Defaults to ``'%'``. | 1213 +--------------+---------------------------------------------+ 1214 | *level* | Set the root logger level to the specified | 1215 | | :ref:`level <levels>`. | 1216 +--------------+---------------------------------------------+ 1217 | *stream* | Use the specified stream to initialize the | 1218 | | :class:`StreamHandler`. Note that this | 1219 | | argument is incompatible with *filename* - | 1220 | | if both are present, a ``ValueError`` is | 1221 | | raised. | 1222 +--------------+---------------------------------------------+ 1223 | *handlers* | If specified, this should be an iterable of | 1224 | | already created handlers to add to the root | 1225 | | logger. Any handlers which don't already | 1226 | | have a formatter set will be assigned the | 1227 | | default formatter created in this function. | 1228 | | Note that this argument is incompatible | 1229 | | with *filename* or *stream* - if both | 1230 | | are present, a ``ValueError`` is raised. | 1231 +--------------+---------------------------------------------+ 1232 | *force* | If this keyword argument is specified as | 1233 | | true, any existing handlers attached to the | 1234 | | root logger are removed and closed, before | 1235 | | carrying out the configuration as specified | 1236 | | by the other arguments. | 1237 +--------------+---------------------------------------------+ 1238 | *encoding* | If this keyword argument is specified along | 1239 | | with *filename*, its value is used when the | 1240 | | :class:`FileHandler` is created, and thus | 1241 | | used when opening the output file. | 1242 +--------------+---------------------------------------------+ 1243 | *errors* | If this keyword argument is specified along | 1244 | | with *filename*, its value is used when the | 1245 | | :class:`FileHandler` is created, and thus | 1246 | | used when opening the output file. If not | 1247 | | specified, the value 'backslashreplace' is | 1248 | | used. Note that if ``None`` is specified, | 1249 | | it will be passed as such to :func:`open`, | 1250 | | which means that it will be treated the | 1251 | | same as passing 'errors'. | 1252 +--------------+---------------------------------------------+ 1253 1254 .. versionchanged:: 3.2 1255 The *style* argument was added. 1256 1257 .. versionchanged:: 3.3 1258 The *handlers* argument was added. Additional checks were added to 1259 catch situations where incompatible arguments are specified (e.g. 1260 *handlers* together with *stream* or *filename*, or *stream* 1261 together with *filename*). 1262 1263 .. versionchanged:: 3.8 1264 The *force* argument was added. 1265 1266 .. versionchanged:: 3.9 1267 The *encoding* and *errors* arguments were added. 1268 1269.. function:: shutdown() 1270 1271 Informs the logging system to perform an orderly shutdown by flushing and 1272 closing all handlers. This should be called at application exit and no 1273 further use of the logging system should be made after this call. 1274 1275 When the logging module is imported, it registers this function as an exit 1276 handler (see :mod:`atexit`), so normally there's no need to do that 1277 manually. 1278 1279 1280.. function:: setLoggerClass(klass) 1281 1282 Tells the logging system to use the class *klass* when instantiating a logger. 1283 The class should define :meth:`__init__` such that only a name argument is 1284 required, and the :meth:`__init__` should call :meth:`Logger.__init__`. This 1285 function is typically called before any loggers are instantiated by applications 1286 which need to use custom logger behavior. After this call, as at any other 1287 time, do not instantiate loggers directly using the subclass: continue to use 1288 the :func:`logging.getLogger` API to get your loggers. 1289 1290 1291.. function:: setLogRecordFactory(factory) 1292 1293 Set a callable which is used to create a :class:`LogRecord`. 1294 1295 :param factory: The factory callable to be used to instantiate a log record. 1296 1297 .. versionadded:: 3.2 1298 This function has been provided, along with :func:`getLogRecordFactory`, to 1299 allow developers more control over how the :class:`LogRecord` representing 1300 a logging event is constructed. 1301 1302 The factory has the following signature: 1303 1304 ``factory(name, level, fn, lno, msg, args, exc_info, func=None, sinfo=None, **kwargs)`` 1305 1306 :name: The logger name. 1307 :level: The logging level (numeric). 1308 :fn: The full pathname of the file where the logging call was made. 1309 :lno: The line number in the file where the logging call was made. 1310 :msg: The logging message. 1311 :args: The arguments for the logging message. 1312 :exc_info: An exception tuple, or ``None``. 1313 :func: The name of the function or method which invoked the logging 1314 call. 1315 :sinfo: A stack traceback such as is provided by 1316 :func:`traceback.print_stack`, showing the call hierarchy. 1317 :kwargs: Additional keyword arguments. 1318 1319 1320Module-Level Attributes 1321----------------------- 1322 1323.. attribute:: lastResort 1324 1325 A "handler of last resort" is available through this attribute. This 1326 is a :class:`StreamHandler` writing to ``sys.stderr`` with a level of 1327 ``WARNING``, and is used to handle logging events in the absence of any 1328 logging configuration. The end result is to just print the message to 1329 ``sys.stderr``. This replaces the earlier error message saying that 1330 "no handlers could be found for logger XYZ". If you need the earlier 1331 behaviour for some reason, ``lastResort`` can be set to ``None``. 1332 1333 .. versionadded:: 3.2 1334 1335Integration with the warnings module 1336------------------------------------ 1337 1338The :func:`captureWarnings` function can be used to integrate :mod:`logging` 1339with the :mod:`warnings` module. 1340 1341.. function:: captureWarnings(capture) 1342 1343 This function is used to turn the capture of warnings by logging on and 1344 off. 1345 1346 If *capture* is ``True``, warnings issued by the :mod:`warnings` module will 1347 be redirected to the logging system. Specifically, a warning will be 1348 formatted using :func:`warnings.formatwarning` and the resulting string 1349 logged to a logger named ``'py.warnings'`` with a severity of :const:`WARNING`. 1350 1351 If *capture* is ``False``, the redirection of warnings to the logging system 1352 will stop, and warnings will be redirected to their original destinations 1353 (i.e. those in effect before ``captureWarnings(True)`` was called). 1354 1355 1356.. seealso:: 1357 1358 Module :mod:`logging.config` 1359 Configuration API for the logging module. 1360 1361 Module :mod:`logging.handlers` 1362 Useful handlers included with the logging module. 1363 1364 :pep:`282` - A Logging System 1365 The proposal which described this feature for inclusion in the Python standard 1366 library. 1367 1368 `Original Python logging package <https://old.red-dove.com/python_logging.html>`_ 1369 This is the original source for the :mod:`logging` package. The version of the 1370 package available from this site is suitable for use with Python 1.5.2, 2.1.x 1371 and 2.2.x, which do not include the :mod:`logging` package in the standard 1372 library. 1373