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 evaluates to true, events logged to this logger will be passed to the 75 handlers of higher level (ancestor) loggers, in addition to any handlers 76 attached to this logger. Messages are passed directly to the ancestor 77 loggers' handlers - neither the level nor filters of the ancestor loggers in 78 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(lvl) 95 96 Sets the threshold for this logger to *lvl*. Logging messages which are less 97 severe than *lvl* will be ignored. When a logger is created, the level is set to 98 :const:`NOTSET` (which causes all messages to be processed when the logger is 99 the root logger, or delegation to the parent when the logger is a non-root 100 logger). Note that the root logger is created with level :const:`WARNING`. 101 102 The term 'delegation to the parent' means that if a logger has a level of 103 NOTSET, its chain of ancestor loggers is traversed until either an ancestor with 104 a level other than NOTSET is found, or the root is reached. 105 106 If an ancestor is found with a level other than NOTSET, then that ancestor's 107 level is treated as the effective level of the logger where the ancestor search 108 began, and is used to determine how a logging event is handled. 109 110 If the root is reached, and it has a level of NOTSET, then all messages will be 111 processed. Otherwise, the root's level will be used as the effective level. 112 113 See :ref:`levels` for a list of levels. 114 115 .. versionchanged:: 3.2 116 The *lvl* parameter now accepts a string representation of the 117 level such as 'INFO' as an alternative to the integer constants 118 such as :const:`INFO`. Note, however, that levels are internally stored 119 as integers, and methods such as e.g. :meth:`getEffectiveLevel` and 120 :meth:`isEnabledFor` will return/expect to be passed integers. 121 122 123 .. method:: Logger.isEnabledFor(lvl) 124 125 Indicates if a message of severity *lvl* would be processed by this logger. 126 This method checks first the module-level level set by 127 ``logging.disable(lvl)`` and then the logger's effective level as determined 128 by :meth:`getEffectiveLevel`. 129 130 131 .. method:: Logger.getEffectiveLevel() 132 133 Indicates the effective level for this logger. If a value other than 134 :const:`NOTSET` has been set using :meth:`setLevel`, it is returned. Otherwise, 135 the hierarchy is traversed towards the root until a value other than 136 :const:`NOTSET` is found, and that value is returned. The value returned is 137 an integer, typically one of :const:`logging.DEBUG`, :const:`logging.INFO` 138 etc. 139 140 141 .. method:: Logger.getChild(suffix) 142 143 Returns a logger which is a descendant to this logger, as determined by the suffix. 144 Thus, ``logging.getLogger('abc').getChild('def.ghi')`` would return the same 145 logger as would be returned by ``logging.getLogger('abc.def.ghi')``. This is a 146 convenience method, useful when the parent logger is named using e.g. ``__name__`` 147 rather than a literal string. 148 149 .. versionadded:: 3.2 150 151 152 .. method:: Logger.debug(msg, *args, **kwargs) 153 154 Logs a message with level :const:`DEBUG` on this logger. The *msg* is the 155 message format string, and the *args* are the arguments which are merged into 156 *msg* using the string formatting operator. (Note that this means that you can 157 use keywords in the format string, together with a single dictionary argument.) 158 159 There are three keyword arguments in *kwargs* which are inspected: 160 *exc_info*, *stack_info*, and *extra*. 161 162 If *exc_info* does not evaluate as false, it causes exception information to be 163 added to the logging message. If an exception tuple (in the format returned by 164 :func:`sys.exc_info`) or an exception instance is provided, it is used; 165 otherwise, :func:`sys.exc_info` is called to get the exception information. 166 167 The second optional keyword argument is *stack_info*, which defaults to 168 ``False``. If true, stack information is added to the logging 169 message, including the actual logging call. Note that this is not the same 170 stack information as that displayed through specifying *exc_info*: The 171 former is stack frames from the bottom of the stack up to the logging call 172 in the current thread, whereas the latter is information about stack frames 173 which have been unwound, following an exception, while searching for 174 exception handlers. 175 176 You can specify *stack_info* independently of *exc_info*, e.g. to just show 177 how you got to a certain point in your code, even when no exceptions were 178 raised. The stack frames are printed following a header line which says:: 179 180 Stack (most recent call last): 181 182 This mimics the ``Traceback (most recent call last):`` which is used when 183 displaying exception frames. 184 185 The third keyword argument is *extra* which can be used to pass a 186 dictionary which is used to populate the __dict__ of the LogRecord created for 187 the logging event with user-defined attributes. These custom attributes can then 188 be used as you like. For example, they could be incorporated into logged 189 messages. For example:: 190 191 FORMAT = '%(asctime)-15s %(clientip)s %(user)-8s %(message)s' 192 logging.basicConfig(format=FORMAT) 193 d = {'clientip': '192.168.0.1', 'user': 'fbloggs'} 194 logger = logging.getLogger('tcpserver') 195 logger.warning('Protocol problem: %s', 'connection reset', extra=d) 196 197 would print something like :: 198 199 2006-02-08 22:20:02,165 192.168.0.1 fbloggs Protocol problem: connection reset 200 201 The keys in the dictionary passed in *extra* should not clash with the keys used 202 by the logging system. (See the :class:`Formatter` documentation for more 203 information on which keys are used by the logging system.) 204 205 If you choose to use these attributes in logged messages, you need to exercise 206 some care. In the above example, for instance, the :class:`Formatter` has been 207 set up with a format string which expects 'clientip' and 'user' in the attribute 208 dictionary of the LogRecord. If these are missing, the message will not be 209 logged because a string formatting exception will occur. So in this case, you 210 always need to pass the *extra* dictionary with these keys. 211 212 While this might be annoying, this feature is intended for use in specialized 213 circumstances, such as multi-threaded servers where the same code executes in 214 many contexts, and interesting conditions which arise are dependent on this 215 context (such as remote client IP address and authenticated user name, in the 216 above example). In such circumstances, it is likely that specialized 217 :class:`Formatter`\ s would be used with particular :class:`Handler`\ s. 218 219 .. versionadded:: 3.2 220 The *stack_info* parameter was added. 221 222 .. versionchanged:: 3.5 223 The *exc_info* parameter can now accept exception instances. 224 225 226 .. method:: Logger.info(msg, *args, **kwargs) 227 228 Logs a message with level :const:`INFO` on this logger. The arguments are 229 interpreted as for :meth:`debug`. 230 231 232 .. method:: Logger.warning(msg, *args, **kwargs) 233 234 Logs a message with level :const:`WARNING` on this logger. The arguments are 235 interpreted as for :meth:`debug`. 236 237 .. note:: There is an obsolete method ``warn`` which is functionally 238 identical to ``warning``. As ``warn`` is deprecated, please do not use 239 it - use ``warning`` instead. 240 241 .. method:: Logger.error(msg, *args, **kwargs) 242 243 Logs a message with level :const:`ERROR` on this logger. The arguments are 244 interpreted as for :meth:`debug`. 245 246 247 .. method:: Logger.critical(msg, *args, **kwargs) 248 249 Logs a message with level :const:`CRITICAL` on this logger. The arguments are 250 interpreted as for :meth:`debug`. 251 252 253 .. method:: Logger.log(lvl, msg, *args, **kwargs) 254 255 Logs a message with integer level *lvl* on this logger. The other arguments are 256 interpreted as for :meth:`debug`. 257 258 259 .. method:: Logger.exception(msg, *args, **kwargs) 260 261 Logs a message with level :const:`ERROR` on this logger. The arguments are 262 interpreted as for :meth:`debug`. Exception info is added to the logging 263 message. This method should only be called from an exception handler. 264 265 266 .. method:: Logger.addFilter(filt) 267 268 Adds the specified filter *filt* to this logger. 269 270 271 .. method:: Logger.removeFilter(filt) 272 273 Removes the specified filter *filt* from this logger. 274 275 276 .. method:: Logger.filter(record) 277 278 Applies this logger's filters to the record and returns a true value if the 279 record is to be processed. The filters are consulted in turn, until one of 280 them returns a false value. If none of them return a false value, the record 281 will be processed (passed to handlers). If one returns a false value, no 282 further processing of the record occurs. 283 284 285 .. method:: Logger.addHandler(hdlr) 286 287 Adds the specified handler *hdlr* to this logger. 288 289 290 .. method:: Logger.removeHandler(hdlr) 291 292 Removes the specified handler *hdlr* from this logger. 293 294 295 .. method:: Logger.findCaller(stack_info=False) 296 297 Finds the caller's source filename and line number. Returns the filename, line 298 number, function name and stack information as a 4-element tuple. The stack 299 information is returned as ``None`` unless *stack_info* is ``True``. 300 301 302 .. method:: Logger.handle(record) 303 304 Handles a record by passing it to all handlers associated with this logger and 305 its ancestors (until a false value of *propagate* is found). This method is used 306 for unpickled records received from a socket, as well as those created locally. 307 Logger-level filtering is applied using :meth:`~Logger.filter`. 308 309 310 .. method:: Logger.makeRecord(name, lvl, fn, lno, msg, args, exc_info, func=None, extra=None, sinfo=None) 311 312 This is a factory method which can be overridden in subclasses to create 313 specialized :class:`LogRecord` instances. 314 315 .. method:: Logger.hasHandlers() 316 317 Checks to see if this logger has any handlers configured. This is done by 318 looking for handlers in this logger and its parents in the logger hierarchy. 319 Returns ``True`` if a handler was found, else ``False``. The method stops searching 320 up the hierarchy whenever a logger with the 'propagate' attribute set to 321 false is found - that will be the last logger which is checked for the 322 existence of handlers. 323 324 .. versionadded:: 3.2 325 326 327 .. _levels: 328 329 Logging Levels 330 -------------- 331 332 The numeric values of logging levels are given in the following table. These are 333 primarily of interest if you want to define your own levels, and need them to 334 have specific values relative to the predefined levels. If you define a level 335 with the same numeric value, it overwrites the predefined value; the predefined 336 name is lost. 337 338 +--------------+---------------+ 339 | Level | Numeric value | 340 +==============+===============+ 341 | ``CRITICAL`` | 50 | 342 +--------------+---------------+ 343 | ``ERROR`` | 40 | 344 +--------------+---------------+ 345 | ``WARNING`` | 30 | 346 +--------------+---------------+ 347 | ``INFO`` | 20 | 348 +--------------+---------------+ 349 | ``DEBUG`` | 10 | 350 +--------------+---------------+ 351 | ``NOTSET`` | 0 | 352 +--------------+---------------+ 353 354 355 .. _handler: 356 357 Handler Objects 358 --------------- 359 360 Handlers have the following attributes and methods. Note that :class:`Handler` 361 is never instantiated directly; this class acts as a base for more useful 362 subclasses. However, the :meth:`__init__` method in subclasses needs to call 363 :meth:`Handler.__init__`. 364 365 366 .. method:: Handler.__init__(level=NOTSET) 367 368 Initializes the :class:`Handler` instance by setting its level, setting the list 369 of filters to the empty list and creating a lock (using :meth:`createLock`) for 370 serializing access to an I/O mechanism. 371 372 373 .. method:: Handler.createLock() 374 375 Initializes a thread lock which can be used to serialize access to underlying 376 I/O functionality which may not be threadsafe. 377 378 379 .. method:: Handler.acquire() 380 381 Acquires the thread lock created with :meth:`createLock`. 382 383 384 .. method:: Handler.release() 385 386 Releases the thread lock acquired with :meth:`acquire`. 387 388 389 .. method:: Handler.setLevel(lvl) 390 391 Sets the threshold for this handler to *lvl*. Logging messages which are less 392 severe than *lvl* will be ignored. When a handler is created, the level is set 393 to :const:`NOTSET` (which causes all messages to be processed). 394 395 See :ref:`levels` for a list of levels. 396 397 .. versionchanged:: 3.2 398 The *lvl* parameter now accepts a string representation of the 399 level such as 'INFO' as an alternative to the integer constants 400 such as :const:`INFO`. 401 402 403 .. method:: Handler.setFormatter(form) 404 405 Sets the :class:`Formatter` for this handler to *form*. 406 407 408 .. method:: Handler.addFilter(filt) 409 410 Adds the specified filter *filt* to this handler. 411 412 413 .. method:: Handler.removeFilter(filt) 414 415 Removes the specified filter *filt* from this handler. 416 417 418 .. method:: Handler.filter(record) 419 420 Applies this handler's filters to the record and returns a true value if the 421 record is to be processed. The filters are consulted in turn, until one of 422 them returns a false value. If none of them return a false value, the record 423 will be emitted. If one returns a false value, the handler will not emit the 424 record. 425 426 427 .. method:: Handler.flush() 428 429 Ensure all logging output has been flushed. This version does nothing and is 430 intended to be implemented by subclasses. 431 432 433 .. method:: Handler.close() 434 435 Tidy up any resources used by the handler. This version does no output but 436 removes the handler from an internal list of handlers which is closed when 437 :func:`shutdown` is called. Subclasses should ensure that this gets called 438 from overridden :meth:`close` methods. 439 440 441 .. method:: Handler.handle(record) 442 443 Conditionally emits the specified logging record, depending on filters which may 444 have been added to the handler. Wraps the actual emission of the record with 445 acquisition/release of the I/O thread lock. 446 447 448 .. method:: Handler.handleError(record) 449 450 This method should be called from handlers when an exception is encountered 451 during an :meth:`emit` call. If the module-level attribute 452 ``raiseExceptions`` is ``False``, exceptions get silently ignored. This is 453 what is mostly wanted for a logging system - most users will not care about 454 errors in the logging system, they are more interested in application 455 errors. You could, however, replace this with a custom handler if you wish. 456 The specified record is the one which was being processed when the exception 457 occurred. (The default value of ``raiseExceptions`` is ``True``, as that is 458 more useful during development). 459 460 461 .. method:: Handler.format(record) 462 463 Do formatting for a record - if a formatter is set, use it. Otherwise, use the 464 default formatter for the module. 465 466 467 .. method:: Handler.emit(record) 468 469 Do whatever it takes to actually log the specified logging record. This version 470 is intended to be implemented by subclasses and so raises a 471 :exc:`NotImplementedError`. 472 473 For a list of handlers included as standard, see :mod:`logging.handlers`. 474 475 .. _formatter-objects: 476 477 Formatter Objects 478 ----------------- 479 480 .. currentmodule:: logging 481 482 :class:`Formatter` objects have the following attributes and methods. They are 483 responsible for converting a :class:`LogRecord` to (usually) a string which can 484 be interpreted by either a human or an external system. The base 485 :class:`Formatter` allows a formatting string to be specified. If none is 486 supplied, the default value of ``'%(message)s'`` is used, which just includes 487 the message in the logging call. To have additional items of information in the 488 formatted output (such as a timestamp), keep reading. 489 490 A Formatter can be initialized with a format string which makes use of knowledge 491 of the :class:`LogRecord` attributes - such as the default value mentioned above 492 making use of the fact that the user's message and arguments are pre-formatted 493 into a :class:`LogRecord`'s *message* attribute. This format string contains 494 standard Python %-style mapping keys. See section :ref:`old-string-formatting` 495 for more information on string formatting. 496 497 The useful mapping keys in a :class:`LogRecord` are given in the section on 498 :ref:`logrecord-attributes`. 499 500 501 .. class:: Formatter(fmt=None, datefmt=None, style='%') 502 503 Returns a new instance of the :class:`Formatter` class. The instance is 504 initialized with a format string for the message as a whole, as well as a 505 format string for the date/time portion of a message. If no *fmt* is 506 specified, ``'%(message)s'`` is used. If no *datefmt* is specified, the 507 ISO8601 date format is used. 508 509 The *style* parameter can be one of '%', '{' or '$' and determines how 510 the format string will be merged with its data: using one of %-formatting, 511 :meth:`str.format` or :class:`string.Template`. See :ref:`formatting-styles` 512 for more information on using {- and $-formatting for log messages. 513 514 .. versionchanged:: 3.2 515 The *style* parameter was added. 516 517 518 .. method:: format(record) 519 520 The record's attribute dictionary is used as the operand to a string 521 formatting operation. Returns the resulting string. Before formatting the 522 dictionary, a couple of preparatory steps are carried out. The *message* 523 attribute of the record is computed using *msg* % *args*. If the 524 formatting string contains ``'(asctime)'``, :meth:`formatTime` is called 525 to format the event time. If there is exception information, it is 526 formatted using :meth:`formatException` and appended to the message. Note 527 that the formatted exception information is cached in attribute 528 *exc_text*. This is useful because the exception information can be 529 pickled and sent across the wire, but you should be careful if you have 530 more than one :class:`Formatter` subclass which customizes the formatting 531 of exception information. In this case, you will have to clear the cached 532 value after a formatter has done its formatting, so that the next 533 formatter to handle the event doesn't use the cached value but 534 recalculates it afresh. 535 536 If stack information is available, it's appended after the exception 537 information, using :meth:`formatStack` to transform it if necessary. 538 539 540 .. method:: formatTime(record, datefmt=None) 541 542 This method should be called from :meth:`format` by a formatter which 543 wants to make use of a formatted time. This method can be overridden in 544 formatters to provide for any specific requirement, but the basic behavior 545 is as follows: if *datefmt* (a string) is specified, it is used with 546 :func:`time.strftime` to format the creation time of the 547 record. Otherwise, the ISO8601 format is used. The resulting string is 548 returned. 549 550 This function uses a user-configurable function to convert the creation 551 time to a tuple. By default, :func:`time.localtime` is used; to change 552 this for a particular formatter instance, set the ``converter`` attribute 553 to a function with the same signature as :func:`time.localtime` or 554 :func:`time.gmtime`. To change it for all formatters, for example if you 555 want all logging times to be shown in GMT, set the ``converter`` 556 attribute in the ``Formatter`` class. 557 558 .. versionchanged:: 3.3 559 Previously, the default ISO 8601 format was hard-coded as in this 560 example: ``2010-09-06 22:38:15,292`` where the part before the comma is 561 handled by a strptime format string (``'%Y-%m-%d %H:%M:%S'``), and the 562 part after the comma is a millisecond value. Because strptime does not 563 have a format placeholder for milliseconds, the millisecond value is 564 appended using another format string, ``'%s,%03d'`` --- and both of these 565 format strings have been hardcoded into this method. With the change, 566 these strings are defined as class-level attributes which can be 567 overridden at the instance level when desired. The names of the 568 attributes are ``default_time_format`` (for the strptime format string) 569 and ``default_msec_format`` (for appending the millisecond value). 570 571 .. method:: formatException(exc_info) 572 573 Formats the specified exception information (a standard exception tuple as 574 returned by :func:`sys.exc_info`) as a string. This default implementation 575 just uses :func:`traceback.print_exception`. The resulting string is 576 returned. 577 578 .. method:: formatStack(stack_info) 579 580 Formats the specified stack information (a string as returned by 581 :func:`traceback.print_stack`, but with the last newline removed) as a 582 string. This default implementation just returns the input value. 583 584 .. _filter: 585 586 Filter Objects 587 -------------- 588 589 ``Filters`` can be used by ``Handlers`` and ``Loggers`` for more sophisticated 590 filtering than is provided by levels. The base filter class only allows events 591 which are below a certain point in the logger hierarchy. For example, a filter 592 initialized with 'A.B' will allow events logged by loggers 'A.B', 'A.B.C', 593 'A.B.C.D', 'A.B.D' etc. but not 'A.BB', 'B.A.B' etc. If initialized with the 594 empty string, all events are passed. 595 596 597 .. class:: Filter(name='') 598 599 Returns an instance of the :class:`Filter` class. If *name* is specified, it 600 names a logger which, together with its children, will have its events allowed 601 through the filter. If *name* is the empty string, allows every event. 602 603 604 .. method:: filter(record) 605 606 Is the specified record to be logged? Returns zero for no, nonzero for 607 yes. If deemed appropriate, the record may be modified in-place by this 608 method. 609 610 Note that filters attached to handlers are consulted before an event is 611 emitted by the handler, whereas filters attached to loggers are consulted 612 whenever an event is logged (using :meth:`debug`, :meth:`info`, 613 etc.), before sending an event to handlers. This means that events which have 614 been generated by descendant loggers will not be filtered by a logger's filter 615 setting, unless the filter has also been applied to those descendant loggers. 616 617 You don't actually need to subclass ``Filter``: you can pass any instance 618 which has a ``filter`` method with the same semantics. 619 620 .. versionchanged:: 3.2 621 You don't need to create specialized ``Filter`` classes, or use other 622 classes with a ``filter`` method: you can use a function (or other 623 callable) as a filter. The filtering logic will check to see if the filter 624 object has a ``filter`` attribute: if it does, it's assumed to be a 625 ``Filter`` and its :meth:`~Filter.filter` method is called. Otherwise, it's 626 assumed to be a callable and called with the record as the single 627 parameter. The returned value should conform to that returned by 628 :meth:`~Filter.filter`. 629 630 Although filters are used primarily to filter records based on more 631 sophisticated criteria than levels, they get to see every record which is 632 processed by the handler or logger they're attached to: this can be useful if 633 you want to do things like counting how many records were processed by a 634 particular logger or handler, or adding, changing or removing attributes in 635 the LogRecord being processed. Obviously changing the LogRecord needs to be 636 done with some care, but it does allow the injection of contextual information 637 into logs (see :ref:`filters-contextual`). 638 639 .. _log-record: 640 641 LogRecord Objects 642 ----------------- 643 644 :class:`LogRecord` instances are created automatically by the :class:`Logger` 645 every time something is logged, and can be created manually via 646 :func:`makeLogRecord` (for example, from a pickled event received over the 647 wire). 648 649 650 .. class:: LogRecord(name, level, pathname, lineno, msg, args, exc_info, func=None, sinfo=None) 651 652 Contains all the information pertinent to the event being logged. 653 654 The primary information is passed in :attr:`msg` and :attr:`args`, which 655 are combined using ``msg % args`` to create the :attr:`message` field of the 656 record. 657 658 :param name: The name of the logger used to log the event represented by 659 this LogRecord. Note that this name will always have this 660 value, even though it may be emitted by a handler attached to 661 a different (ancestor) logger. 662 :param level: The numeric level of the logging event (one of DEBUG, INFO etc.) 663 Note that this is converted to *two* attributes of the LogRecord: 664 ``levelno`` for the numeric value and ``levelname`` for the 665 corresponding level name. 666 :param pathname: The full pathname of the source file where the logging call 667 was made. 668 :param lineno: The line number in the source file where the logging call was 669 made. 670 :param msg: The event description message, possibly a format string with 671 placeholders for variable data. 672 :param args: Variable data to merge into the *msg* argument to obtain the 673 event description. 674 :param exc_info: An exception tuple with the current exception information, 675 or ``None`` if no exception information is available. 676 :param func: The name of the function or method from which the logging call 677 was invoked. 678 :param sinfo: A text string representing stack information from the base of 679 the stack in the current thread, up to the logging call. 680 681 .. method:: getMessage() 682 683 Returns the message for this :class:`LogRecord` instance after merging any 684 user-supplied arguments with the message. If the user-supplied message 685 argument to the logging call is not a string, :func:`str` is called on it to 686 convert it to a string. This allows use of user-defined classes as 687 messages, whose ``__str__`` method can return the actual format string to 688 be used. 689 690 .. versionchanged:: 3.2 691 The creation of a ``LogRecord`` has been made more configurable by 692 providing a factory which is used to create the record. The factory can be 693 set using :func:`getLogRecordFactory` and :func:`setLogRecordFactory` 694 (see this for the factory's signature). 695 696 This functionality can be used to inject your own values into a 697 LogRecord at creation time. You can use the following pattern:: 698 699 old_factory = logging.getLogRecordFactory() 700 701 def record_factory(*args, **kwargs): 702 record = old_factory(*args, **kwargs) 703 record.custom_attribute = 0xdecafbad 704 return record 705 706 logging.setLogRecordFactory(record_factory) 707 708 With this pattern, multiple factories could be chained, and as long 709 as they don't overwrite each other's attributes or unintentionally 710 overwrite the standard attributes listed above, there should be no 711 surprises. 712 713 714 .. _logrecord-attributes: 715 716 LogRecord attributes 717 -------------------- 718 719 The LogRecord has a number of attributes, most of which are derived from the 720 parameters to the constructor. (Note that the names do not always correspond 721 exactly between the LogRecord constructor parameters and the LogRecord 722 attributes.) These attributes can be used to merge data from the record into 723 the format string. The following table lists (in alphabetical order) the 724 attribute names, their meanings and the corresponding placeholder in a %-style 725 format string. 726 727 If you are using {}-formatting (:func:`str.format`), you can use 728 ``{attrname}`` as the placeholder in the format string. If you are using 729 $-formatting (:class:`string.Template`), use the form ``${attrname}``. In 730 both cases, of course, replace ``attrname`` with the actual attribute name 731 you want to use. 732 733 In the case of {}-formatting, you can specify formatting flags by placing them 734 after the attribute name, separated from it with a colon. For example: a 735 placeholder of ``{msecs:03d}`` would format a millisecond value of ``4`` as 736 ``004``. Refer to the :meth:`str.format` documentation for full details on 737 the options available to you. 738 739 +----------------+-------------------------+-----------------------------------------------+ 740 | Attribute name | Format | Description | 741 +================+=========================+===============================================+ 742 | args | You shouldn't need to | The tuple of arguments merged into ``msg`` to | 743 | | format this yourself. | produce ``message``, or a dict whose values | 744 | | | are used for the merge (when there is only one| 745 | | | argument, and it is a dictionary). | 746 +----------------+-------------------------+-----------------------------------------------+ 747 | asctime | ``%(asctime)s`` | Human-readable time when the | 748 | | | :class:`LogRecord` was created. By default | 749 | | | this is of the form '2003-07-08 16:49:45,896' | 750 | | | (the numbers after the comma are millisecond | 751 | | | portion of the time). | 752 +----------------+-------------------------+-----------------------------------------------+ 753 | created | ``%(created)f`` | Time when the :class:`LogRecord` was created | 754 | | | (as returned by :func:`time.time`). | 755 +----------------+-------------------------+-----------------------------------------------+ 756 | exc_info | You shouldn't need to | Exception tuple ( la ``sys.exc_info``) or, | 757 | | format this yourself. | if no exception has occurred, ``None``. | 758 +----------------+-------------------------+-----------------------------------------------+ 759 | filename | ``%(filename)s`` | Filename portion of ``pathname``. | 760 +----------------+-------------------------+-----------------------------------------------+ 761 | funcName | ``%(funcName)s`` | Name of function containing the logging call. | 762 +----------------+-------------------------+-----------------------------------------------+ 763 | levelname | ``%(levelname)s`` | Text logging level for the message | 764 | | | (``'DEBUG'``, ``'INFO'``, ``'WARNING'``, | 765 | | | ``'ERROR'``, ``'CRITICAL'``). | 766 +----------------+-------------------------+-----------------------------------------------+ 767 | levelno | ``%(levelno)s`` | Numeric logging level for the message | 768 | | | (:const:`DEBUG`, :const:`INFO`, | 769 | | | :const:`WARNING`, :const:`ERROR`, | 770 | | | :const:`CRITICAL`). | 771 +----------------+-------------------------+-----------------------------------------------+ 772 | lineno | ``%(lineno)d`` | Source line number where the logging call was | 773 | | | issued (if available). | 774 +----------------+-------------------------+-----------------------------------------------+ 775 | module | ``%(module)s`` | Module (name portion of ``filename``). | 776 +----------------+-------------------------+-----------------------------------------------+ 777 | msecs | ``%(msecs)d`` | Millisecond portion of the time when the | 778 | | | :class:`LogRecord` was created. | 779 +----------------+-------------------------+-----------------------------------------------+ 780 | message | ``%(message)s`` | The logged message, computed as ``msg % | 781 | | | args``. This is set when | 782 | | | :meth:`Formatter.format` is invoked. | 783 +----------------+-------------------------+-----------------------------------------------+ 784 | msg | You shouldn't need to | The format string passed in the original | 785 | | format this yourself. | logging call. Merged with ``args`` to | 786 | | | produce ``message``, or an arbitrary object | 787 | | | (see :ref:`arbitrary-object-messages`). | 788 +----------------+-------------------------+-----------------------------------------------+ 789 | name | ``%(name)s`` | Name of the logger used to log the call. | 790 +----------------+-------------------------+-----------------------------------------------+ 791 | pathname | ``%(pathname)s`` | Full pathname of the source file where the | 792 | | | logging call was issued (if available). | 793 +----------------+-------------------------+-----------------------------------------------+ 794 | process | ``%(process)d`` | Process ID (if available). | 795 +----------------+-------------------------+-----------------------------------------------+ 796 | processName | ``%(processName)s`` | Process name (if available). | 797 +----------------+-------------------------+-----------------------------------------------+ 798 | relativeCreated| ``%(relativeCreated)d`` | Time in milliseconds when the LogRecord was | 799 | | | created, relative to the time the logging | 800 | | | module was loaded. | 801 +----------------+-------------------------+-----------------------------------------------+ 802 | stack_info | You shouldn't need to | Stack frame information (where available) | 803 | | format this yourself. | from the bottom of the stack in the current | 804 | | | thread, up to and including the stack frame | 805 | | | of the logging call which resulted in the | 806 | | | creation of this record. | 807 +----------------+-------------------------+-----------------------------------------------+ 808 | thread | ``%(thread)d`` | Thread ID (if available). | 809 +----------------+-------------------------+-----------------------------------------------+ 810 | threadName | ``%(threadName)s`` | Thread name (if available). | 811 +----------------+-------------------------+-----------------------------------------------+ 812 813 .. versionchanged:: 3.1 814 *processName* was added. 815 816 817 .. _logger-adapter: 818 819 LoggerAdapter Objects 820 --------------------- 821 822 :class:`LoggerAdapter` instances are used to conveniently pass contextual 823 information into logging calls. For a usage example, see the section on 824 :ref:`adding contextual information to your logging output <context-info>`. 825 826 .. class:: LoggerAdapter(logger, extra) 827 828 Returns an instance of :class:`LoggerAdapter` initialized with an 829 underlying :class:`Logger` instance and a dict-like object. 830 831 .. method:: process(msg, kwargs) 832 833 Modifies the message and/or keyword arguments passed to a logging call in 834 order to insert contextual information. This implementation takes the object 835 passed as *extra* to the constructor and adds it to *kwargs* using key 836 'extra'. The return value is a (*msg*, *kwargs*) tuple which has the 837 (possibly modified) versions of the arguments passed in. 838 839 In addition to the above, :class:`LoggerAdapter` supports the following 840 methods of :class:`Logger`: :meth:`~Logger.debug`, :meth:`~Logger.info`, 841 :meth:`~Logger.warning`, :meth:`~Logger.error`, :meth:`~Logger.exception`, 842 :meth:`~Logger.critical`, :meth:`~Logger.log`, :meth:`~Logger.isEnabledFor`, 843 :meth:`~Logger.getEffectiveLevel`, :meth:`~Logger.setLevel` and 844 :meth:`~Logger.hasHandlers`. These methods have the same signatures as their 845 counterparts in :class:`Logger`, so you can use the two types of instances 846 interchangeably. 847 848 .. versionchanged:: 3.2 849 The :meth:`~Logger.isEnabledFor`, :meth:`~Logger.getEffectiveLevel`, 850 :meth:`~Logger.setLevel` and :meth:`~Logger.hasHandlers` methods were added 851 to :class:`LoggerAdapter`. These methods delegate to the underlying logger. 852 853 854 Thread Safety 855 ------------- 856 857 The logging module is intended to be thread-safe without any special work 858 needing to be done by its clients. It achieves this though using threading 859 locks; there is one lock to serialize access to the module's shared data, and 860 each handler also creates a lock to serialize access to its underlying I/O. 861 862 If you are implementing asynchronous signal handlers using the :mod:`signal` 863 module, you may not be able to use logging from within such handlers. This is 864 because lock implementations in the :mod:`threading` module are not always 865 re-entrant, and so cannot be invoked from such signal handlers. 866 867 868 Module-Level Functions 869 ---------------------- 870 871 In addition to the classes described above, there are a number of module- level 872 functions. 873 874 875 .. function:: getLogger(name=None) 876 877 Return a logger with the specified name or, if name is ``None``, return a 878 logger which is the root logger of the hierarchy. If specified, the name is 879 typically a dot-separated hierarchical name like *'a'*, *'a.b'* or *'a.b.c.d'*. 880 Choice of these names is entirely up to the developer who is using logging. 881 882 All calls to this function with a given name return the same logger instance. 883 This means that logger instances never need to be passed between different parts 884 of an application. 885 886 887 .. function:: getLoggerClass() 888 889 Return either the standard :class:`Logger` class, or the last class passed to 890 :func:`setLoggerClass`. This function may be called from within a new class 891 definition, to ensure that installing a customized :class:`Logger` class will 892 not undo customizations already applied by other code. For example:: 893 894 class MyLogger(logging.getLoggerClass()): 895 # ... override behaviour here 896 897 898 .. function:: getLogRecordFactory() 899 900 Return a callable which is used to create a :class:`LogRecord`. 901 902 .. versionadded:: 3.2 903 This function has been provided, along with :func:`setLogRecordFactory`, 904 to allow developers more control over how the :class:`LogRecord` 905 representing a logging event is constructed. 906 907 See :func:`setLogRecordFactory` for more information about the how the 908 factory is called. 909 910 .. function:: debug(msg, *args, **kwargs) 911 912 Logs a message with level :const:`DEBUG` on the root logger. The *msg* is the 913 message format string, and the *args* are the arguments which are merged into 914 *msg* using the string formatting operator. (Note that this means that you can 915 use keywords in the format string, together with a single dictionary argument.) 916 917 There are three keyword arguments in *kwargs* which are inspected: *exc_info* 918 which, if it does not evaluate as false, causes exception information to be 919 added to the logging message. If an exception tuple (in the format returned by 920 :func:`sys.exc_info`) is provided, it is used; otherwise, :func:`sys.exc_info` 921 is called to get the exception information. 922 923 The second optional keyword argument is *stack_info*, which defaults to 924 ``False``. If true, stack information is added to the logging 925 message, including the actual logging call. Note that this is not the same 926 stack information as that displayed through specifying *exc_info*: The 927 former is stack frames from the bottom of the stack up to the logging call 928 in the current thread, whereas the latter is information about stack frames 929 which have been unwound, following an exception, while searching for 930 exception handlers. 931 932 You can specify *stack_info* independently of *exc_info*, e.g. to just show 933 how you got to a certain point in your code, even when no exceptions were 934 raised. The stack frames are printed following a header line which says:: 935 936 Stack (most recent call last): 937 938 This mimics the ``Traceback (most recent call last):`` which is used when 939 displaying exception frames. 940 941 The third optional keyword argument is *extra* which can be used to pass a 942 dictionary which is used to populate the __dict__ of the LogRecord created for 943 the logging event with user-defined attributes. These custom attributes can then 944 be used as you like. For example, they could be incorporated into logged 945 messages. For example:: 946 947 FORMAT = '%(asctime)-15s %(clientip)s %(user)-8s %(message)s' 948 logging.basicConfig(format=FORMAT) 949 d = {'clientip': '192.168.0.1', 'user': 'fbloggs'} 950 logging.warning('Protocol problem: %s', 'connection reset', extra=d) 951 952 would print something like:: 953 954 2006-02-08 22:20:02,165 192.168.0.1 fbloggs Protocol problem: connection reset 955 956 The keys in the dictionary passed in *extra* should not clash with the keys used 957 by the logging system. (See the :class:`Formatter` documentation for more 958 information on which keys are used by the logging system.) 959 960 If you choose to use these attributes in logged messages, you need to exercise 961 some care. In the above example, for instance, the :class:`Formatter` has been 962 set up with a format string which expects 'clientip' and 'user' in the attribute 963 dictionary of the LogRecord. If these are missing, the message will not be 964 logged because a string formatting exception will occur. So in this case, you 965 always need to pass the *extra* dictionary with these keys. 966 967 While this might be annoying, this feature is intended for use in specialized 968 circumstances, such as multi-threaded servers where the same code executes in 969 many contexts, and interesting conditions which arise are dependent on this 970 context (such as remote client IP address and authenticated user name, in the 971 above example). In such circumstances, it is likely that specialized 972 :class:`Formatter`\ s would be used with particular :class:`Handler`\ s. 973 974 .. versionadded:: 3.2 975 The *stack_info* parameter was added. 976 977 .. function:: info(msg, *args, **kwargs) 978 979 Logs a message with level :const:`INFO` on the root logger. The arguments are 980 interpreted as for :func:`debug`. 981 982 983 .. function:: warning(msg, *args, **kwargs) 984 985 Logs a message with level :const:`WARNING` on the root logger. The arguments 986 are interpreted as for :func:`debug`. 987 988 .. note:: There is an obsolete function ``warn`` which is functionally 989 identical to ``warning``. As ``warn`` is deprecated, please do not use 990 it - use ``warning`` instead. 991 992 993 .. function:: error(msg, *args, **kwargs) 994 995 Logs a message with level :const:`ERROR` on the root logger. The arguments are 996 interpreted as for :func:`debug`. 997 998 999 .. function:: critical(msg, *args, **kwargs) 1000 1001 Logs a message with level :const:`CRITICAL` on the root logger. The arguments 1002 are interpreted as for :func:`debug`. 1003 1004 1005 .. function:: exception(msg, *args, **kwargs) 1006 1007 Logs a message with level :const:`ERROR` on the root logger. The arguments are 1008 interpreted as for :func:`debug`. Exception info is added to the logging 1009 message. This function should only be called from an exception handler. 1010 1011 .. function:: log(level, msg, *args, **kwargs) 1012 1013 Logs a message with level *level* on the root logger. The other arguments are 1014 interpreted as for :func:`debug`. 1015 1016 .. note:: The above module-level convenience functions, which delegate to the 1017 root logger, call :func:`basicConfig` to ensure that at least one handler 1018 is available. Because of this, they should *not* be used in threads, 1019 in versions of Python earlier than 2.7.1 and 3.2, unless at least one 1020 handler has been added to the root logger *before* the threads are 1021 started. In earlier versions of Python, due to a thread safety shortcoming 1022 in :func:`basicConfig`, this can (under rare circumstances) lead to 1023 handlers being added multiple times to the root logger, which can in turn 1024 lead to multiple messages for the same event. 1025 1026 .. function:: disable(lvl) 1027 1028 Provides an overriding level *lvl* for all loggers which takes precedence over 1029 the logger's own level. When the need arises to temporarily throttle logging 1030 output down across the whole application, this function can be useful. Its 1031 effect is to disable all logging calls of severity *lvl* and below, so that 1032 if you call it with a value of INFO, then all INFO and DEBUG events would be 1033 discarded, whereas those of severity WARNING and above would be processed 1034 according to the logger's effective level. If 1035 ``logging.disable(logging.NOTSET)`` is called, it effectively removes this 1036 overriding level, so that logging output again depends on the effective 1037 levels of individual loggers. 1038 1039 1040 .. function:: addLevelName(lvl, levelName) 1041 1042 Associates level *lvl* with text *levelName* in an internal dictionary, which is 1043 used to map numeric levels to a textual representation, for example when a 1044 :class:`Formatter` formats a message. This function can also be used to define 1045 your own levels. The only constraints are that all levels used must be 1046 registered using this function, levels should be positive integers and they 1047 should increase in increasing order of severity. 1048 1049 .. note:: If you are thinking of defining your own levels, please see the 1050 section on :ref:`custom-levels`. 1051 1052 .. function:: getLevelName(lvl) 1053 1054 Returns the textual representation of logging level *lvl*. If the level is one 1055 of the predefined levels :const:`CRITICAL`, :const:`ERROR`, :const:`WARNING`, 1056 :const:`INFO` or :const:`DEBUG` then you get the corresponding string. If you 1057 have associated levels with names using :func:`addLevelName` then the name you 1058 have associated with *lvl* is returned. If a numeric value corresponding to one 1059 of the defined levels is passed in, the corresponding string representation is 1060 returned. Otherwise, the string 'Level %s' % lvl is returned. 1061 1062 .. note:: Levels are internally integers (as they need to be compared in the 1063 logging logic). This function is used to convert between an integer level 1064 and the level name displayed in the formatted log output by means of the 1065 ``%(levelname)s`` format specifier (see :ref:`logrecord-attributes`). 1066 1067 .. versionchanged:: 3.4 1068 In Python versions earlier than 3.4, this function could also be passed a 1069 text level, and would return the corresponding numeric value of the level. 1070 This undocumented behaviour was considered a mistake, and was removed in 1071 Python 3.4, but reinstated in 3.4.2 due to retain backward compatibility. 1072 1073 .. function:: makeLogRecord(attrdict) 1074 1075 Creates and returns a new :class:`LogRecord` instance whose attributes are 1076 defined by *attrdict*. This function is useful for taking a pickled 1077 :class:`LogRecord` attribute dictionary, sent over a socket, and reconstituting 1078 it as a :class:`LogRecord` instance at the receiving end. 1079 1080 1081 .. function:: basicConfig(**kwargs) 1082 1083 Does basic configuration for the logging system by creating a 1084 :class:`StreamHandler` with a default :class:`Formatter` and adding it to the 1085 root logger. The functions :func:`debug`, :func:`info`, :func:`warning`, 1086 :func:`error` and :func:`critical` will call :func:`basicConfig` automatically 1087 if no handlers are defined for the root logger. 1088 1089 This function does nothing if the root logger already has handlers 1090 configured for it. 1091 1092 .. note:: This function should be called from the main thread 1093 before other threads are started. In versions of Python prior to 1094 2.7.1 and 3.2, if this function is called from multiple threads, 1095 it is possible (in rare circumstances) that a handler will be added 1096 to the root logger more than once, leading to unexpected results 1097 such as messages being duplicated in the log. 1098 1099 The following keyword arguments are supported. 1100 1101 .. tabularcolumns:: |l|L| 1102 1103 +--------------+---------------------------------------------+ 1104 | Format | Description | 1105 +==============+=============================================+ 1106 | ``filename`` | Specifies that a FileHandler be created, | 1107 | | using the specified filename, rather than a | 1108 | | StreamHandler. | 1109 +--------------+---------------------------------------------+ 1110 | ``filemode`` | Specifies the mode to open the file, if | 1111 | | filename is specified (if filemode is | 1112 | | unspecified, it defaults to 'a'). | 1113 +--------------+---------------------------------------------+ 1114 | ``format`` | Use the specified format string for the | 1115 | | handler. | 1116 +--------------+---------------------------------------------+ 1117 | ``datefmt`` | Use the specified date/time format. | 1118 +--------------+---------------------------------------------+ 1119 | ``style`` | If ``format`` is specified, use this style | 1120 | | for the format string. One of '%', '{' or | 1121 | | '$' for %-formatting, :meth:`str.format` or | 1122 | | :class:`string.Template` respectively, and | 1123 | | defaulting to '%' if not specified. | 1124 +--------------+---------------------------------------------+ 1125 | ``level`` | Set the root logger level to the specified | 1126 | | level. | 1127 +--------------+---------------------------------------------+ 1128 | ``stream`` | Use the specified stream to initialize the | 1129 | | StreamHandler. Note that this argument is | 1130 | | incompatible with 'filename' - if both are | 1131 | | present, a ``ValueError`` is raised. | 1132 +--------------+---------------------------------------------+ 1133 | ``handlers`` | If specified, this should be an iterable of | 1134 | | already created handlers to add to the root | 1135 | | logger. Any handlers which don't already | 1136 | | have a formatter set will be assigned the | 1137 | | default formatter created in this function. | 1138 | | Note that this argument is incompatible | 1139 | | with 'filename' or 'stream' - if both are | 1140 | | present, a ``ValueError`` is raised. | 1141 +--------------+---------------------------------------------+ 1142 1143 .. versionchanged:: 3.2 1144 The ``style`` argument was added. 1145 1146 .. versionchanged:: 3.3 1147 The ``handlers`` argument was added. Additional checks were added to 1148 catch situations where incompatible arguments are specified (e.g. 1149 ``handlers`` together with ``stream`` or ``filename``, or ``stream`` 1150 together with ``filename``). 1151 1152 1153 .. function:: shutdown() 1154 1155 Informs the logging system to perform an orderly shutdown by flushing and 1156 closing all handlers. This should be called at application exit and no 1157 further use of the logging system should be made after this call. 1158 1159 1160 .. function:: setLoggerClass(klass) 1161 1162 Tells the logging system to use the class *klass* when instantiating a logger. 1163 The class should define :meth:`__init__` such that only a name argument is 1164 required, and the :meth:`__init__` should call :meth:`Logger.__init__`. This 1165 function is typically called before any loggers are instantiated by applications 1166 which need to use custom logger behavior. 1167 1168 1169 .. function:: setLogRecordFactory(factory) 1170 1171 Set a callable which is used to create a :class:`LogRecord`. 1172 1173 :param factory: The factory callable to be used to instantiate a log record. 1174 1175 .. versionadded:: 3.2 1176 This function has been provided, along with :func:`getLogRecordFactory`, to 1177 allow developers more control over how the :class:`LogRecord` representing 1178 a logging event is constructed. 1179 1180 The factory has the following signature: 1181 1182 ``factory(name, level, fn, lno, msg, args, exc_info, func=None, sinfo=None, **kwargs)`` 1183 1184 :name: The logger name. 1185 :level: The logging level (numeric). 1186 :fn: The full pathname of the file where the logging call was made. 1187 :lno: The line number in the file where the logging call was made. 1188 :msg: The logging message. 1189 :args: The arguments for the logging message. 1190 :exc_info: An exception tuple, or ``None``. 1191 :func: The name of the function or method which invoked the logging 1192 call. 1193 :sinfo: A stack traceback such as is provided by 1194 :func:`traceback.print_stack`, showing the call hierarchy. 1195 :kwargs: Additional keyword arguments. 1196 1197 1198 Module-Level Attributes 1199 ----------------------- 1200 1201 .. attribute:: lastResort 1202 1203 A "handler of last resort" is available through this attribute. This 1204 is a :class:`StreamHandler` writing to ``sys.stderr`` with a level of 1205 ``WARNING``, and is used to handle logging events in the absence of any 1206 logging configuration. The end result is to just print the message to 1207 ``sys.stderr``. This replaces the earlier error message saying that 1208 "no handlers could be found for logger XYZ". If you need the earlier 1209 behaviour for some reason, ``lastResort`` can be set to ``None``. 1210 1211 .. versionadded:: 3.2 1212 1213 Integration with the warnings module 1214 ------------------------------------ 1215 1216 The :func:`captureWarnings` function can be used to integrate :mod:`logging` 1217 with the :mod:`warnings` module. 1218 1219 .. function:: captureWarnings(capture) 1220 1221 This function is used to turn the capture of warnings by logging on and 1222 off. 1223 1224 If *capture* is ``True``, warnings issued by the :mod:`warnings` module will 1225 be redirected to the logging system. Specifically, a warning will be 1226 formatted using :func:`warnings.formatwarning` and the resulting string 1227 logged to a logger named ``'py.warnings'`` with a severity of :const:`WARNING`. 1228 1229 If *capture* is ``False``, the redirection of warnings to the logging system 1230 will stop, and warnings will be redirected to their original destinations 1231 (i.e. those in effect before ``captureWarnings(True)`` was called). 1232 1233 1234 .. seealso:: 1235 1236 Module :mod:`logging.config` 1237 Configuration API for the logging module. 1238 1239 Module :mod:`logging.handlers` 1240 Useful handlers included with the logging module. 1241 1242 :pep:`282` - A Logging System 1243 The proposal which described this feature for inclusion in the Python standard 1244 library. 1245 1246 `Original Python logging package <https://www.red-dove.com/python_logging.html>`_ 1247 This is the original source for the :mod:`logging` package. The version of the 1248 package available from this site is suitable for use with Python 1.5.2, 2.1.x 1249 and 2.2.x, which do not include the :mod:`logging` package in the standard 1250 library. 1251 1252
