Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1 | :mod:`logging` --- Logging facility for Python |
| 2 | ============================================== |
| 3 | |
| 4 | .. module:: logging |
Vinay Sajip | 1d5d685 | 2010-12-12 22:47:13 +0000 | [diff] [blame] | 5 | :synopsis: Flexible event logging system for applications. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 6 | |
| 7 | |
| 8 | .. moduleauthor:: Vinay Sajip <vinay_sajip@red-dove.com> |
| 9 | .. sectionauthor:: Vinay Sajip <vinay_sajip@red-dove.com> |
| 10 | |
| 11 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 12 | .. index:: pair: Errors; logging |
| 13 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 14 | .. sidebar:: Important |
| 15 | |
Vinay Sajip | 01094e1 | 2010-12-19 13:41:26 +0000 | [diff] [blame] | 16 | This page contains the API reference information. For tutorial |
| 17 | information and discussion of more advanced topics, see |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 18 | |
| 19 | * :ref:`Basic Tutorial <logging-basic-tutorial>` |
| 20 | * :ref:`Advanced Tutorial <logging-advanced-tutorial>` |
| 21 | * :ref:`Logging Cookbook <logging-cookbook>` |
| 22 | |
| 23 | |
Vinay Sajip | 1d5d685 | 2010-12-12 22:47:13 +0000 | [diff] [blame] | 24 | This module defines functions and classes which implement a flexible event |
Vinay Sajip | 36675b6 | 2010-12-12 22:30:17 +0000 | [diff] [blame] | 25 | logging system for applications and libraries. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 26 | |
Vinay Sajip | a18b959 | 2010-12-12 13:20:55 +0000 | [diff] [blame] | 27 | The key benefit of having the logging API provided by a standard library module |
| 28 | is that all Python modules can participate in logging, so your application log |
| 29 | can include your own messages integrated with messages from third-party |
| 30 | modules. |
| 31 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 32 | The module provides a lot of functionality and flexibility. If you are |
| 33 | unfamiliar with logging, the best way to get to grips with it is to see the |
Vinay Sajip | 01094e1 | 2010-12-19 13:41:26 +0000 | [diff] [blame] | 34 | tutorials (see the links on the right). |
Vinay Sajip | a18b959 | 2010-12-12 13:20:55 +0000 | [diff] [blame] | 35 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 36 | The basic classes defined by the module, together with their functions, are |
| 37 | listed below. |
Vinay Sajip | 9a6b400 | 2010-12-14 19:40:21 +0000 | [diff] [blame] | 38 | |
| 39 | * Loggers expose the interface that application code directly uses. |
| 40 | * Handlers send the log records (created by loggers) to the appropriate |
| 41 | destination. |
| 42 | * Filters provide a finer grained facility for determining which log records |
| 43 | to output. |
| 44 | * Formatters specify the layout of log records in the final output. |
Vinay Sajip | a18b959 | 2010-12-12 13:20:55 +0000 | [diff] [blame] | 45 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 46 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 47 | .. _logger: |
Vinay Sajip | 5286ccf | 2010-12-12 13:25:29 +0000 | [diff] [blame] | 48 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 49 | Logger Objects |
Christian Heimes | 8b0facf | 2007-12-04 19:30:01 +0000 | [diff] [blame] | 50 | -------------- |
| 51 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 52 | Loggers have the following attributes and methods. Note that Loggers are never |
| 53 | instantiated directly, but always through the module-level function |
| 54 | ``logging.getLogger(name)``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 55 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 56 | .. class:: Logger |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 57 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 58 | .. attribute:: Logger.propagate |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 59 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 60 | If this evaluates to false, logging messages are not passed by this logger or by |
| 61 | its child loggers to the handlers of higher level (ancestor) loggers. The |
| 62 | constructor sets this attribute to 1. |
Vinay Sajip | c8c8c69 | 2010-09-17 10:09:04 +0000 | [diff] [blame] | 63 | |
| 64 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 65 | .. method:: Logger.setLevel(lvl) |
Vinay Sajip | f234eb9 | 2010-12-12 17:37:27 +0000 | [diff] [blame] | 66 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 67 | Sets the threshold for this logger to *lvl*. Logging messages which are less |
| 68 | severe than *lvl* will be ignored. When a logger is created, the level is set to |
| 69 | :const:`NOTSET` (which causes all messages to be processed when the logger is |
| 70 | the root logger, or delegation to the parent when the logger is a non-root |
| 71 | logger). Note that the root logger is created with level :const:`WARNING`. |
| 72 | |
| 73 | The term 'delegation to the parent' means that if a logger has a level of |
| 74 | NOTSET, its chain of ancestor loggers is traversed until either an ancestor with |
| 75 | a level other than NOTSET is found, or the root is reached. |
| 76 | |
| 77 | If an ancestor is found with a level other than NOTSET, then that ancestor's |
| 78 | level is treated as the effective level of the logger where the ancestor search |
| 79 | began, and is used to determine how a logging event is handled. |
| 80 | |
| 81 | If the root is reached, and it has a level of NOTSET, then all messages will be |
| 82 | processed. Otherwise, the root's level will be used as the effective level. |
| 83 | |
| 84 | |
| 85 | .. method:: Logger.isEnabledFor(lvl) |
| 86 | |
| 87 | Indicates if a message of severity *lvl* would be processed by this logger. |
| 88 | This method checks first the module-level level set by |
| 89 | ``logging.disable(lvl)`` and then the logger's effective level as determined |
| 90 | by :meth:`getEffectiveLevel`. |
| 91 | |
| 92 | |
| 93 | .. method:: Logger.getEffectiveLevel() |
| 94 | |
| 95 | Indicates the effective level for this logger. If a value other than |
| 96 | :const:`NOTSET` has been set using :meth:`setLevel`, it is returned. Otherwise, |
| 97 | the hierarchy is traversed towards the root until a value other than |
| 98 | :const:`NOTSET` is found, and that value is returned. |
| 99 | |
| 100 | |
| 101 | .. method:: Logger.getChild(suffix) |
| 102 | |
| 103 | Returns a logger which is a descendant to this logger, as determined by the suffix. |
| 104 | Thus, ``logging.getLogger('abc').getChild('def.ghi')`` would return the same |
| 105 | logger as would be returned by ``logging.getLogger('abc.def.ghi')``. This is a |
| 106 | convenience method, useful when the parent logger is named using e.g. ``__name__`` |
| 107 | rather than a literal string. |
| 108 | |
| 109 | .. versionadded:: 3.2 |
| 110 | |
| 111 | |
| 112 | .. method:: Logger.debug(msg, *args, **kwargs) |
| 113 | |
| 114 | Logs a message with level :const:`DEBUG` on this logger. The *msg* is the |
| 115 | message format string, and the *args* are the arguments which are merged into |
| 116 | *msg* using the string formatting operator. (Note that this means that you can |
| 117 | use keywords in the format string, together with a single dictionary argument.) |
| 118 | |
| 119 | There are three keyword arguments in *kwargs* which are inspected: *exc_info* |
| 120 | which, if it does not evaluate as false, causes exception information to be |
| 121 | added to the logging message. If an exception tuple (in the format returned by |
| 122 | :func:`sys.exc_info`) is provided, it is used; otherwise, :func:`sys.exc_info` |
| 123 | is called to get the exception information. |
| 124 | |
| 125 | The second optional keyword argument is *stack_info*, which defaults to |
| 126 | False. If specified as True, stack information is added to the logging |
| 127 | message, including the actual logging call. Note that this is not the same |
| 128 | stack information as that displayed through specifying *exc_info*: The |
| 129 | former is stack frames from the bottom of the stack up to the logging call |
| 130 | in the current thread, whereas the latter is information about stack frames |
| 131 | which have been unwound, following an exception, while searching for |
| 132 | exception handlers. |
| 133 | |
| 134 | You can specify *stack_info* independently of *exc_info*, e.g. to just show |
| 135 | how you got to a certain point in your code, even when no exceptions were |
| 136 | raised. The stack frames are printed following a header line which says:: |
| 137 | |
| 138 | Stack (most recent call last): |
| 139 | |
| 140 | This mimics the `Traceback (most recent call last):` which is used when |
| 141 | displaying exception frames. |
| 142 | |
| 143 | The third keyword argument is *extra* which can be used to pass a |
| 144 | dictionary which is used to populate the __dict__ of the LogRecord created for |
| 145 | the logging event with user-defined attributes. These custom attributes can then |
| 146 | be used as you like. For example, they could be incorporated into logged |
| 147 | messages. For example:: |
| 148 | |
| 149 | FORMAT = '%(asctime)-15s %(clientip)s %(user)-8s %(message)s' |
| 150 | logging.basicConfig(format=FORMAT) |
| 151 | d = { 'clientip' : '192.168.0.1', 'user' : 'fbloggs' } |
| 152 | logger = logging.getLogger('tcpserver') |
| 153 | logger.warning('Protocol problem: %s', 'connection reset', extra=d) |
| 154 | |
| 155 | would print something like :: |
| 156 | |
| 157 | 2006-02-08 22:20:02,165 192.168.0.1 fbloggs Protocol problem: connection reset |
| 158 | |
| 159 | The keys in the dictionary passed in *extra* should not clash with the keys used |
| 160 | by the logging system. (See the :class:`Formatter` documentation for more |
| 161 | information on which keys are used by the logging system.) |
| 162 | |
| 163 | If you choose to use these attributes in logged messages, you need to exercise |
| 164 | some care. In the above example, for instance, the :class:`Formatter` has been |
| 165 | set up with a format string which expects 'clientip' and 'user' in the attribute |
| 166 | dictionary of the LogRecord. If these are missing, the message will not be |
| 167 | logged because a string formatting exception will occur. So in this case, you |
| 168 | always need to pass the *extra* dictionary with these keys. |
| 169 | |
| 170 | While this might be annoying, this feature is intended for use in specialized |
| 171 | circumstances, such as multi-threaded servers where the same code executes in |
| 172 | many contexts, and interesting conditions which arise are dependent on this |
| 173 | context (such as remote client IP address and authenticated user name, in the |
| 174 | above example). In such circumstances, it is likely that specialized |
| 175 | :class:`Formatter`\ s would be used with particular :class:`Handler`\ s. |
| 176 | |
| 177 | .. versionadded:: 3.2 |
| 178 | The *stack_info* parameter was added. |
| 179 | |
| 180 | |
| 181 | .. method:: Logger.info(msg, *args, **kwargs) |
| 182 | |
| 183 | Logs a message with level :const:`INFO` on this logger. The arguments are |
| 184 | interpreted as for :meth:`debug`. |
| 185 | |
| 186 | |
| 187 | .. method:: Logger.warning(msg, *args, **kwargs) |
| 188 | |
| 189 | Logs a message with level :const:`WARNING` on this logger. The arguments are |
| 190 | interpreted as for :meth:`debug`. |
| 191 | |
| 192 | |
| 193 | .. method:: Logger.error(msg, *args, **kwargs) |
| 194 | |
| 195 | Logs a message with level :const:`ERROR` on this logger. The arguments are |
| 196 | interpreted as for :meth:`debug`. |
| 197 | |
| 198 | |
| 199 | .. method:: Logger.critical(msg, *args, **kwargs) |
| 200 | |
| 201 | Logs a message with level :const:`CRITICAL` on this logger. The arguments are |
| 202 | interpreted as for :meth:`debug`. |
| 203 | |
| 204 | |
| 205 | .. method:: Logger.log(lvl, msg, *args, **kwargs) |
| 206 | |
| 207 | Logs a message with integer level *lvl* on this logger. The other arguments are |
| 208 | interpreted as for :meth:`debug`. |
| 209 | |
| 210 | |
| 211 | .. method:: Logger.exception(msg, *args) |
| 212 | |
| 213 | Logs a message with level :const:`ERROR` on this logger. The arguments are |
| 214 | interpreted as for :meth:`debug`. Exception info is added to the logging |
| 215 | message. This method should only be called from an exception handler. |
| 216 | |
| 217 | |
| 218 | .. method:: Logger.addFilter(filt) |
| 219 | |
| 220 | Adds the specified filter *filt* to this logger. |
| 221 | |
| 222 | |
| 223 | .. method:: Logger.removeFilter(filt) |
| 224 | |
| 225 | Removes the specified filter *filt* from this logger. |
| 226 | |
| 227 | |
| 228 | .. method:: Logger.filter(record) |
| 229 | |
| 230 | Applies this logger's filters to the record and returns a true value if the |
| 231 | record is to be processed. |
| 232 | |
| 233 | |
| 234 | .. method:: Logger.addHandler(hdlr) |
| 235 | |
| 236 | Adds the specified handler *hdlr* to this logger. |
| 237 | |
| 238 | |
| 239 | .. method:: Logger.removeHandler(hdlr) |
| 240 | |
| 241 | Removes the specified handler *hdlr* from this logger. |
| 242 | |
| 243 | |
| 244 | .. method:: Logger.findCaller(stack_info=False) |
| 245 | |
| 246 | Finds the caller's source filename and line number. Returns the filename, line |
| 247 | number, function name and stack information as a 4-element tuple. The stack |
| 248 | information is returned as *None* unless *stack_info* is *True*. |
| 249 | |
| 250 | |
| 251 | .. method:: Logger.handle(record) |
| 252 | |
| 253 | Handles a record by passing it to all handlers associated with this logger and |
| 254 | its ancestors (until a false value of *propagate* is found). This method is used |
| 255 | for unpickled records received from a socket, as well as those created locally. |
| 256 | Logger-level filtering is applied using :meth:`~Logger.filter`. |
| 257 | |
| 258 | |
| 259 | .. method:: Logger.makeRecord(name, lvl, fn, lno, msg, args, exc_info, func=None, extra=None, sinfo=None) |
| 260 | |
| 261 | This is a factory method which can be overridden in subclasses to create |
| 262 | specialized :class:`LogRecord` instances. |
| 263 | |
| 264 | .. method:: Logger.hasHandlers() |
| 265 | |
| 266 | Checks to see if this logger has any handlers configured. This is done by |
| 267 | looking for handlers in this logger and its parents in the logger hierarchy. |
| 268 | Returns True if a handler was found, else False. The method stops searching |
| 269 | up the hierarchy whenever a logger with the 'propagate' attribute set to |
| 270 | False is found - that will be the last logger which is checked for the |
| 271 | existence of handlers. |
| 272 | |
| 273 | .. versionadded:: 3.2 |
| 274 | |
| 275 | |
| 276 | .. _handler: |
| 277 | |
| 278 | Handler Objects |
Benjamin Peterson | 058e31e | 2009-01-16 03:54:08 +0000 | [diff] [blame] | 279 | --------------- |
| 280 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 281 | Handlers have the following attributes and methods. Note that :class:`Handler` |
| 282 | is never instantiated directly; this class acts as a base for more useful |
| 283 | subclasses. However, the :meth:`__init__` method in subclasses needs to call |
| 284 | :meth:`Handler.__init__`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 285 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 286 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 287 | .. method:: Handler.__init__(level=NOTSET) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 288 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 289 | Initializes the :class:`Handler` instance by setting its level, setting the list |
| 290 | of filters to the empty list and creating a lock (using :meth:`createLock`) for |
| 291 | serializing access to an I/O mechanism. |
Vinay Sajip | 30bf122 | 2009-01-10 19:23:34 +0000 | [diff] [blame] | 292 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 293 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 294 | .. method:: Handler.createLock() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 295 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 296 | Initializes a thread lock which can be used to serialize access to underlying |
| 297 | I/O functionality which may not be threadsafe. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 298 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 299 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 300 | .. method:: Handler.acquire() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 301 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 302 | Acquires the thread lock created with :meth:`createLock`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 303 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 304 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 305 | .. method:: Handler.release() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 306 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 307 | Releases the thread lock acquired with :meth:`acquire`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 308 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 309 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 310 | .. method:: Handler.setLevel(lvl) |
Vinay Sajip | 30bf122 | 2009-01-10 19:23:34 +0000 | [diff] [blame] | 311 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 312 | Sets the threshold for this handler to *lvl*. Logging messages which are less |
| 313 | severe than *lvl* will be ignored. When a handler is created, the level is set |
| 314 | to :const:`NOTSET` (which causes all messages to be processed). |
| 315 | |
| 316 | |
| 317 | .. method:: Handler.setFormatter(form) |
| 318 | |
| 319 | Sets the :class:`Formatter` for this handler to *form*. |
| 320 | |
| 321 | |
| 322 | .. method:: Handler.addFilter(filt) |
| 323 | |
| 324 | Adds the specified filter *filt* to this handler. |
| 325 | |
| 326 | |
| 327 | .. method:: Handler.removeFilter(filt) |
| 328 | |
| 329 | Removes the specified filter *filt* from this handler. |
| 330 | |
| 331 | |
| 332 | .. method:: Handler.filter(record) |
| 333 | |
| 334 | Applies this handler's filters to the record and returns a true value if the |
| 335 | record is to be processed. |
| 336 | |
| 337 | |
| 338 | .. method:: Handler.flush() |
| 339 | |
| 340 | Ensure all logging output has been flushed. This version does nothing and is |
| 341 | intended to be implemented by subclasses. |
| 342 | |
| 343 | |
| 344 | .. method:: Handler.close() |
| 345 | |
| 346 | Tidy up any resources used by the handler. This version does no output but |
| 347 | removes the handler from an internal list of handlers which is closed when |
| 348 | :func:`shutdown` is called. Subclasses should ensure that this gets called |
| 349 | from overridden :meth:`close` methods. |
| 350 | |
| 351 | |
| 352 | .. method:: Handler.handle(record) |
| 353 | |
| 354 | Conditionally emits the specified logging record, depending on filters which may |
| 355 | have been added to the handler. Wraps the actual emission of the record with |
| 356 | acquisition/release of the I/O thread lock. |
| 357 | |
| 358 | |
| 359 | .. method:: Handler.handleError(record) |
| 360 | |
| 361 | This method should be called from handlers when an exception is encountered |
| 362 | during an :meth:`emit` call. By default it does nothing, which means that |
| 363 | exceptions get silently ignored. This is what is mostly wanted for a logging |
| 364 | system - most users will not care about errors in the logging system, they are |
| 365 | more interested in application errors. You could, however, replace this with a |
| 366 | custom handler if you wish. The specified record is the one which was being |
| 367 | processed when the exception occurred. |
| 368 | |
| 369 | |
| 370 | .. method:: Handler.format(record) |
| 371 | |
| 372 | Do formatting for a record - if a formatter is set, use it. Otherwise, use the |
| 373 | default formatter for the module. |
| 374 | |
| 375 | |
| 376 | .. method:: Handler.emit(record) |
| 377 | |
| 378 | Do whatever it takes to actually log the specified logging record. This version |
| 379 | is intended to be implemented by subclasses and so raises a |
| 380 | :exc:`NotImplementedError`. |
| 381 | |
| 382 | For a list of handlers included as standard, see :mod:`logging.handlers`. |
| 383 | |
| 384 | .. _formatter-objects: |
| 385 | |
| 386 | Formatter Objects |
| 387 | ----------------- |
Vinay Sajip | 121a1c4 | 2010-09-08 10:46:15 +0000 | [diff] [blame] | 388 | |
Vinay Sajip | 30bf122 | 2009-01-10 19:23:34 +0000 | [diff] [blame] | 389 | .. currentmodule:: logging |
| 390 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 391 | :class:`Formatter` objects have the following attributes and methods. They are |
| 392 | responsible for converting a :class:`LogRecord` to (usually) a string which can |
| 393 | be interpreted by either a human or an external system. The base |
| 394 | :class:`Formatter` allows a formatting string to be specified. If none is |
| 395 | supplied, the default value of ``'%(message)s'`` is used. |
Georg Brandl | f973407 | 2008-12-07 15:30:06 +0000 | [diff] [blame] | 396 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 397 | A Formatter can be initialized with a format string which makes use of knowledge |
| 398 | of the :class:`LogRecord` attributes - such as the default value mentioned above |
| 399 | making use of the fact that the user's message and arguments are pre-formatted |
| 400 | into a :class:`LogRecord`'s *message* attribute. This format string contains |
| 401 | standard Python %-style mapping keys. See section :ref:`old-string-formatting` |
| 402 | for more information on string formatting. |
Georg Brandl | f973407 | 2008-12-07 15:30:06 +0000 | [diff] [blame] | 403 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 404 | The useful mapping keys in a :class:`LogRecord` are given in the section on |
| 405 | :ref:`logrecord-attributes`. |
Vinay Sajip | 121a1c4 | 2010-09-08 10:46:15 +0000 | [diff] [blame] | 406 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 407 | |
Vinay Sajip | c46102c | 2011-04-08 01:30:51 +0100 | [diff] [blame] | 408 | .. class:: Formatter(fmt=None, datefmt=None, style='%') |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 409 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 410 | Returns a new instance of the :class:`Formatter` class. The instance is |
| 411 | initialized with a format string for the message as a whole, as well as a |
| 412 | format string for the date/time portion of a message. If no *fmt* is |
| 413 | specified, ``'%(message)s'`` is used. If no *datefmt* is specified, the |
| 414 | ISO8601 date format is used. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 415 | |
Vinay Sajip | c46102c | 2011-04-08 01:30:51 +0100 | [diff] [blame] | 416 | The *style* parameter can be one of '%', '{' or '$' and determines how |
| 417 | the format string will be merged with its data: using one of %-formatting, |
Vinay Sajip | 77f8d29 | 2011-04-08 01:34:20 +0100 | [diff] [blame] | 418 | :meth:`str.format` or :class:`string.Template`. |
Vinay Sajip | c46102c | 2011-04-08 01:30:51 +0100 | [diff] [blame] | 419 | |
| 420 | .. versionchanged:: 3.2 |
| 421 | The *style* parameter was added. |
| 422 | |
| 423 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 424 | .. method:: format(record) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 425 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 426 | The record's attribute dictionary is used as the operand to a string |
| 427 | formatting operation. Returns the resulting string. Before formatting the |
| 428 | dictionary, a couple of preparatory steps are carried out. The *message* |
| 429 | attribute of the record is computed using *msg* % *args*. If the |
| 430 | formatting string contains ``'(asctime)'``, :meth:`formatTime` is called |
| 431 | to format the event time. If there is exception information, it is |
| 432 | formatted using :meth:`formatException` and appended to the message. Note |
| 433 | that the formatted exception information is cached in attribute |
| 434 | *exc_text*. This is useful because the exception information can be |
| 435 | pickled and sent across the wire, but you should be careful if you have |
| 436 | more than one :class:`Formatter` subclass which customizes the formatting |
| 437 | of exception information. In this case, you will have to clear the cached |
| 438 | value after a formatter has done its formatting, so that the next |
| 439 | formatter to handle the event doesn't use the cached value but |
| 440 | recalculates it afresh. |
| 441 | |
| 442 | If stack information is available, it's appended after the exception |
| 443 | information, using :meth:`formatStack` to transform it if necessary. |
| 444 | |
| 445 | |
| 446 | .. method:: formatTime(record, datefmt=None) |
| 447 | |
| 448 | This method should be called from :meth:`format` by a formatter which |
| 449 | wants to make use of a formatted time. This method can be overridden in |
| 450 | formatters to provide for any specific requirement, but the basic behavior |
| 451 | is as follows: if *datefmt* (a string) is specified, it is used with |
| 452 | :func:`time.strftime` to format the creation time of the |
| 453 | record. Otherwise, the ISO8601 format is used. The resulting string is |
| 454 | returned. |
| 455 | |
| 456 | |
| 457 | .. method:: formatException(exc_info) |
| 458 | |
| 459 | Formats the specified exception information (a standard exception tuple as |
| 460 | returned by :func:`sys.exc_info`) as a string. This default implementation |
| 461 | just uses :func:`traceback.print_exception`. The resulting string is |
| 462 | returned. |
| 463 | |
| 464 | .. method:: formatStack(stack_info) |
| 465 | |
| 466 | Formats the specified stack information (a string as returned by |
| 467 | :func:`traceback.print_stack`, but with the last newline removed) as a |
| 468 | string. This default implementation just returns the input value. |
| 469 | |
| 470 | .. _filter: |
| 471 | |
| 472 | Filter Objects |
| 473 | -------------- |
| 474 | |
| 475 | ``Filters`` can be used by ``Handlers`` and ``Loggers`` for more sophisticated |
| 476 | filtering than is provided by levels. The base filter class only allows events |
| 477 | which are below a certain point in the logger hierarchy. For example, a filter |
| 478 | initialized with 'A.B' will allow events logged by loggers 'A.B', 'A.B.C', |
| 479 | 'A.B.C.D', 'A.B.D' etc. but not 'A.BB', 'B.A.B' etc. If initialized with the |
| 480 | empty string, all events are passed. |
| 481 | |
| 482 | |
| 483 | .. class:: Filter(name='') |
| 484 | |
| 485 | Returns an instance of the :class:`Filter` class. If *name* is specified, it |
| 486 | names a logger which, together with its children, will have its events allowed |
| 487 | through the filter. If *name* is the empty string, allows every event. |
| 488 | |
| 489 | |
| 490 | .. method:: filter(record) |
| 491 | |
| 492 | Is the specified record to be logged? Returns zero for no, nonzero for |
| 493 | yes. If deemed appropriate, the record may be modified in-place by this |
| 494 | method. |
| 495 | |
| 496 | Note that filters attached to handlers are consulted whenever an event is |
| 497 | emitted by the handler, whereas filters attached to loggers are consulted |
| 498 | whenever an event is logged to the handler (using :meth:`debug`, :meth:`info`, |
| 499 | etc.) This means that events which have been generated by descendant loggers |
| 500 | will not be filtered by a logger's filter setting, unless the filter has also |
| 501 | been applied to those descendant loggers. |
| 502 | |
| 503 | You don't actually need to subclass ``Filter``: you can pass any instance |
| 504 | which has a ``filter`` method with the same semantics. |
| 505 | |
| 506 | .. versionchanged:: 3.2 |
| 507 | You don't need to create specialized ``Filter`` classes, or use other |
| 508 | classes with a ``filter`` method: you can use a function (or other |
| 509 | callable) as a filter. The filtering logic will check to see if the filter |
| 510 | object has a ``filter`` attribute: if it does, it's assumed to be a |
| 511 | ``Filter`` and its :meth:`~Filter.filter` method is called. Otherwise, it's |
| 512 | assumed to be a callable and called with the record as the single |
| 513 | parameter. The returned value should conform to that returned by |
| 514 | :meth:`~Filter.filter`. |
| 515 | |
| 516 | Although filters are used primarily to filter records based on more |
| 517 | sophisticated criteria than levels, they get to see every record which is |
| 518 | processed by the handler or logger they're attached to: this can be useful if |
| 519 | you want to do things like counting how many records were processed by a |
| 520 | particular logger or handler, or adding, changing or removing attributes in |
| 521 | the LogRecord being processed. Obviously changing the LogRecord needs to be |
| 522 | done with some care, but it does allow the injection of contextual information |
| 523 | into logs (see :ref:`filters-contextual`). |
| 524 | |
| 525 | .. _log-record: |
| 526 | |
| 527 | LogRecord Objects |
| 528 | ----------------- |
| 529 | |
| 530 | :class:`LogRecord` instances are created automatically by the :class:`Logger` |
| 531 | every time something is logged, and can be created manually via |
| 532 | :func:`makeLogRecord` (for example, from a pickled event received over the |
| 533 | wire). |
| 534 | |
| 535 | |
| 536 | .. class:: LogRecord(name, level, pathname, lineno, msg, args, exc_info, func=None, sinfo=None) |
| 537 | |
| 538 | Contains all the information pertinent to the event being logged. |
| 539 | |
| 540 | The primary information is passed in :attr:`msg` and :attr:`args`, which |
| 541 | are combined using ``msg % args`` to create the :attr:`message` field of the |
| 542 | record. |
| 543 | |
| 544 | :param name: The name of the logger used to log the event represented by |
| 545 | this LogRecord. |
| 546 | :param level: The numeric level of the logging event (one of DEBUG, INFO etc.) |
| 547 | :param pathname: The full pathname of the source file where the logging call |
| 548 | was made. |
| 549 | :param lineno: The line number in the source file where the logging call was |
| 550 | made. |
| 551 | :param msg: The event description message, possibly a format string with |
| 552 | placeholders for variable data. |
| 553 | :param args: Variable data to merge into the *msg* argument to obtain the |
| 554 | event description. |
| 555 | :param exc_info: An exception tuple with the current exception information, |
| 556 | or *None* if no exception information is available. |
| 557 | :param func: The name of the function or method from which the logging call |
| 558 | was invoked. |
| 559 | :param sinfo: A text string representing stack information from the base of |
| 560 | the stack in the current thread, up to the logging call. |
| 561 | |
| 562 | .. method:: getMessage() |
| 563 | |
| 564 | Returns the message for this :class:`LogRecord` instance after merging any |
| 565 | user-supplied arguments with the message. If the user-supplied message |
| 566 | argument to the logging call is not a string, :func:`str` is called on it to |
| 567 | convert it to a string. This allows use of user-defined classes as |
| 568 | messages, whose ``__str__`` method can return the actual format string to |
| 569 | be used. |
| 570 | |
| 571 | .. versionchanged:: 3.2 |
| 572 | The creation of a ``LogRecord`` has been made more configurable by |
| 573 | providing a factory which is used to create the record. The factory can be |
| 574 | set using :func:`getLogRecordFactory` and :func:`setLogRecordFactory` |
| 575 | (see this for the factory's signature). |
| 576 | |
| 577 | This functionality can be used to inject your own values into a |
| 578 | LogRecord at creation time. You can use the following pattern:: |
| 579 | |
| 580 | old_factory = logging.getLogRecordFactory() |
| 581 | |
| 582 | def record_factory(*args, **kwargs): |
| 583 | record = old_factory(*args, **kwargs) |
| 584 | record.custom_attribute = 0xdecafbad |
| 585 | return record |
| 586 | |
| 587 | logging.setLogRecordFactory(record_factory) |
| 588 | |
| 589 | With this pattern, multiple factories could be chained, and as long |
| 590 | as they don't overwrite each other's attributes or unintentionally |
| 591 | overwrite the standard attributes listed above, there should be no |
| 592 | surprises. |
| 593 | |
| 594 | |
| 595 | .. _logrecord-attributes: |
| 596 | |
| 597 | LogRecord attributes |
| 598 | -------------------- |
| 599 | |
| 600 | The LogRecord has a number of attributes, most of which are derived from the |
| 601 | parameters to the constructor. (Note that the names do not always correspond |
| 602 | exactly between the LogRecord constructor parameters and the LogRecord |
| 603 | attributes.) These attributes can be used to merge data from the record into |
| 604 | the format string. The following table lists (in alphabetical order) the |
| 605 | attribute names, their meanings and the corresponding placeholder in a %-style |
| 606 | format string. |
| 607 | |
| 608 | If you are using {}-formatting (:func:`str.format`), you can use |
| 609 | ``{attrname}`` as the placeholder in the format string. If you are using |
| 610 | $-formatting (:class:`string.Template`), use the form ``${attrname}``. In |
| 611 | both cases, of course, replace ``attrname`` with the actual attribute name |
| 612 | you want to use. |
| 613 | |
| 614 | In the case of {}-formatting, you can specify formatting flags by placing them |
| 615 | after the attribute name, separated from it with a colon. For example: a |
| 616 | placeholder of ``{msecs:03d}`` would format a millisecond value of ``4`` as |
| 617 | ``004``. Refer to the :meth:`str.format` documentation for full details on |
| 618 | the options available to you. |
| 619 | |
| 620 | +----------------+-------------------------+-----------------------------------------------+ |
| 621 | | Attribute name | Format | Description | |
| 622 | +================+=========================+===============================================+ |
| 623 | | args | You shouldn't need to | The tuple of arguments merged into ``msg`` to | |
| 624 | | | format this yourself. | produce ``message``. | |
| 625 | +----------------+-------------------------+-----------------------------------------------+ |
| 626 | | asctime | ``%(asctime)s`` | Human-readable time when the | |
| 627 | | | | :class:`LogRecord` was created. By default | |
| 628 | | | | this is of the form '2003-07-08 16:49:45,896' | |
| 629 | | | | (the numbers after the comma are millisecond | |
| 630 | | | | portion of the time). | |
| 631 | +----------------+-------------------------+-----------------------------------------------+ |
| 632 | | created | ``%(created)f`` | Time when the :class:`LogRecord` was created | |
| 633 | | | | (as returned by :func:`time.time`). | |
| 634 | +----------------+-------------------------+-----------------------------------------------+ |
| 635 | | exc_info | You shouldn't need to | Exception tuple (Ã la ``sys.exc_info``) or, | |
| 636 | | | format this yourself. | if no exception has occurred, *None*. | |
| 637 | +----------------+-------------------------+-----------------------------------------------+ |
| 638 | | filename | ``%(filename)s`` | Filename portion of ``pathname``. | |
| 639 | +----------------+-------------------------+-----------------------------------------------+ |
| 640 | | funcName | ``%(funcName)s`` | Name of function containing the logging call. | |
| 641 | +----------------+-------------------------+-----------------------------------------------+ |
| 642 | | levelname | ``%(levelname)s`` | Text logging level for the message | |
| 643 | | | | (``'DEBUG'``, ``'INFO'``, ``'WARNING'``, | |
| 644 | | | | ``'ERROR'``, ``'CRITICAL'``). | |
| 645 | +----------------+-------------------------+-----------------------------------------------+ |
| 646 | | levelno | ``%(levelno)s`` | Numeric logging level for the message | |
| 647 | | | | (:const:`DEBUG`, :const:`INFO`, | |
| 648 | | | | :const:`WARNING`, :const:`ERROR`, | |
| 649 | | | | :const:`CRITICAL`). | |
| 650 | +----------------+-------------------------+-----------------------------------------------+ |
| 651 | | lineno | ``%(lineno)d`` | Source line number where the logging call was | |
| 652 | | | | issued (if available). | |
| 653 | +----------------+-------------------------+-----------------------------------------------+ |
| 654 | | module | ``%(module)s`` | Module (name portion of ``filename``). | |
| 655 | +----------------+-------------------------+-----------------------------------------------+ |
| 656 | | msecs | ``%(msecs)d`` | Millisecond portion of the time when the | |
| 657 | | | | :class:`LogRecord` was created. | |
| 658 | +----------------+-------------------------+-----------------------------------------------+ |
| 659 | | message | ``%(message)s`` | The logged message, computed as ``msg % | |
| 660 | | | | args``. This is set when | |
| 661 | | | | :meth:`Formatter.format` is invoked. | |
| 662 | +----------------+-------------------------+-----------------------------------------------+ |
| 663 | | msg | You shouldn't need to | The format string passed in the original | |
| 664 | | | format this yourself. | logging call. Merged with ``args`` to | |
| 665 | | | | produce ``message``, or an arbitrary object | |
| 666 | | | | (see :ref:`arbitrary-object-messages`). | |
| 667 | +----------------+-------------------------+-----------------------------------------------+ |
| 668 | | name | ``%(name)s`` | Name of the logger used to log the call. | |
| 669 | +----------------+-------------------------+-----------------------------------------------+ |
| 670 | | pathname | ``%(pathname)s`` | Full pathname of the source file where the | |
| 671 | | | | logging call was issued (if available). | |
| 672 | +----------------+-------------------------+-----------------------------------------------+ |
| 673 | | process | ``%(process)d`` | Process ID (if available). | |
| 674 | +----------------+-------------------------+-----------------------------------------------+ |
| 675 | | processName | ``%(processName)s`` | Process name (if available). | |
| 676 | +----------------+-------------------------+-----------------------------------------------+ |
| 677 | | relativeCreated| ``%(relativeCreated)d`` | Time in milliseconds when the LogRecord was | |
| 678 | | | | created, relative to the time the logging | |
| 679 | | | | module was loaded. | |
| 680 | +----------------+-------------------------+-----------------------------------------------+ |
| 681 | | stack_info | You shouldn't need to | Stack frame information (where available) | |
| 682 | | | format this yourself. | from the bottom of the stack in the current | |
| 683 | | | | thread, up to and including the stack frame | |
| 684 | | | | of the logging call which resulted in the | |
| 685 | | | | creation of this record. | |
| 686 | +----------------+-------------------------+-----------------------------------------------+ |
| 687 | | thread | ``%(thread)d`` | Thread ID (if available). | |
| 688 | +----------------+-------------------------+-----------------------------------------------+ |
| 689 | | threadName | ``%(threadName)s`` | Thread name (if available). | |
| 690 | +----------------+-------------------------+-----------------------------------------------+ |
| 691 | |
| 692 | |
| 693 | .. _logger-adapter: |
| 694 | |
| 695 | LoggerAdapter Objects |
| 696 | --------------------- |
| 697 | |
| 698 | :class:`LoggerAdapter` instances are used to conveniently pass contextual |
| 699 | information into logging calls. For a usage example , see the section on |
| 700 | :ref:`adding contextual information to your logging output <context-info>`. |
| 701 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 702 | .. class:: LoggerAdapter(logger, extra) |
| 703 | |
| 704 | Returns an instance of :class:`LoggerAdapter` initialized with an |
| 705 | underlying :class:`Logger` instance and a dict-like object. |
| 706 | |
| 707 | .. method:: process(msg, kwargs) |
| 708 | |
| 709 | Modifies the message and/or keyword arguments passed to a logging call in |
| 710 | order to insert contextual information. This implementation takes the object |
| 711 | passed as *extra* to the constructor and adds it to *kwargs* using key |
| 712 | 'extra'. The return value is a (*msg*, *kwargs*) tuple which has the |
| 713 | (possibly modified) versions of the arguments passed in. |
| 714 | |
| 715 | In addition to the above, :class:`LoggerAdapter` supports the following |
| 716 | methods of :class:`Logger`, i.e. :meth:`debug`, :meth:`info`, :meth:`warning`, |
| 717 | :meth:`error`, :meth:`exception`, :meth:`critical`, :meth:`log`, |
| 718 | :meth:`isEnabledFor`, :meth:`getEffectiveLevel`, :meth:`setLevel`, |
| 719 | :meth:`hasHandlers`. These methods have the same signatures as their |
| 720 | counterparts in :class:`Logger`, so you can use the two types of instances |
| 721 | interchangeably. |
| 722 | |
| 723 | .. versionchanged:: 3.2 |
| 724 | The :meth:`isEnabledFor`, :meth:`getEffectiveLevel`, :meth:`setLevel` and |
| 725 | :meth:`hasHandlers` methods were added to :class:`LoggerAdapter`. These |
| 726 | methods delegate to the underlying logger. |
| 727 | |
| 728 | |
| 729 | Thread Safety |
| 730 | ------------- |
| 731 | |
| 732 | The logging module is intended to be thread-safe without any special work |
| 733 | needing to be done by its clients. It achieves this though using threading |
| 734 | locks; there is one lock to serialize access to the module's shared data, and |
| 735 | each handler also creates a lock to serialize access to its underlying I/O. |
| 736 | |
| 737 | If you are implementing asynchronous signal handlers using the :mod:`signal` |
| 738 | module, you may not be able to use logging from within such handlers. This is |
| 739 | because lock implementations in the :mod:`threading` module are not always |
| 740 | re-entrant, and so cannot be invoked from such signal handlers. |
| 741 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 742 | |
Benjamin Peterson | 058e31e | 2009-01-16 03:54:08 +0000 | [diff] [blame] | 743 | Module-Level Functions |
| 744 | ---------------------- |
| 745 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 746 | In addition to the classes described above, there are a number of module- level |
| 747 | functions. |
| 748 | |
| 749 | |
Georg Brandl | cd7f32b | 2009-06-08 09:13:45 +0000 | [diff] [blame] | 750 | .. function:: getLogger(name=None) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 751 | |
Georg Brandl | cd7f32b | 2009-06-08 09:13:45 +0000 | [diff] [blame] | 752 | Return a logger with the specified name or, if name is ``None``, return a |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 753 | logger which is the root logger of the hierarchy. If specified, the name is |
Vinay Sajip | 9a6b400 | 2010-12-14 19:40:21 +0000 | [diff] [blame] | 754 | typically a dot-separated hierarchical name like *'a'*, *'a.b'* or *'a.b.c.d'*. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 755 | Choice of these names is entirely up to the developer who is using logging. |
| 756 | |
| 757 | All calls to this function with a given name return the same logger instance. |
| 758 | This means that logger instances never need to be passed between different parts |
| 759 | of an application. |
| 760 | |
| 761 | |
| 762 | .. function:: getLoggerClass() |
| 763 | |
| 764 | Return either the standard :class:`Logger` class, or the last class passed to |
| 765 | :func:`setLoggerClass`. This function may be called from within a new class |
| 766 | definition, to ensure that installing a customised :class:`Logger` class will |
| 767 | not undo customisations already applied by other code. For example:: |
| 768 | |
| 769 | class MyLogger(logging.getLoggerClass()): |
| 770 | # ... override behaviour here |
| 771 | |
| 772 | |
Vinay Sajip | 6156152 | 2010-12-03 11:50:38 +0000 | [diff] [blame] | 773 | .. function:: getLogRecordFactory() |
| 774 | |
| 775 | Return a callable which is used to create a :class:`LogRecord`. |
| 776 | |
| 777 | .. versionadded:: 3.2 |
Vinay Sajip | 6156152 | 2010-12-03 11:50:38 +0000 | [diff] [blame] | 778 | This function has been provided, along with :func:`setLogRecordFactory`, |
| 779 | to allow developers more control over how the :class:`LogRecord` |
| 780 | representing a logging event is constructed. |
| 781 | |
| 782 | See :func:`setLogRecordFactory` for more information about the how the |
| 783 | factory is called. |
| 784 | |
Georg Brandl | cd7f32b | 2009-06-08 09:13:45 +0000 | [diff] [blame] | 785 | .. function:: debug(msg, *args, **kwargs) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 786 | |
| 787 | Logs a message with level :const:`DEBUG` on the root logger. The *msg* is the |
| 788 | message format string, and the *args* are the arguments which are merged into |
| 789 | *msg* using the string formatting operator. (Note that this means that you can |
| 790 | use keywords in the format string, together with a single dictionary argument.) |
| 791 | |
Vinay Sajip | 8593ae6 | 2010-11-14 21:33:04 +0000 | [diff] [blame] | 792 | There are three keyword arguments in *kwargs* which are inspected: *exc_info* |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 793 | which, if it does not evaluate as false, causes exception information to be |
| 794 | added to the logging message. If an exception tuple (in the format returned by |
| 795 | :func:`sys.exc_info`) is provided, it is used; otherwise, :func:`sys.exc_info` |
| 796 | is called to get the exception information. |
| 797 | |
Vinay Sajip | 8593ae6 | 2010-11-14 21:33:04 +0000 | [diff] [blame] | 798 | The second optional keyword argument is *stack_info*, which defaults to |
| 799 | False. If specified as True, stack information is added to the logging |
| 800 | message, including the actual logging call. Note that this is not the same |
| 801 | stack information as that displayed through specifying *exc_info*: The |
| 802 | former is stack frames from the bottom of the stack up to the logging call |
| 803 | in the current thread, whereas the latter is information about stack frames |
| 804 | which have been unwound, following an exception, while searching for |
| 805 | exception handlers. |
| 806 | |
| 807 | You can specify *stack_info* independently of *exc_info*, e.g. to just show |
| 808 | how you got to a certain point in your code, even when no exceptions were |
| 809 | raised. The stack frames are printed following a header line which says:: |
| 810 | |
| 811 | Stack (most recent call last): |
| 812 | |
| 813 | This mimics the `Traceback (most recent call last):` which is used when |
| 814 | displaying exception frames. |
| 815 | |
| 816 | The third optional keyword argument is *extra* which can be used to pass a |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 817 | dictionary which is used to populate the __dict__ of the LogRecord created for |
| 818 | the logging event with user-defined attributes. These custom attributes can then |
| 819 | be used as you like. For example, they could be incorporated into logged |
| 820 | messages. For example:: |
| 821 | |
Vinay Sajip | 9a6b400 | 2010-12-14 19:40:21 +0000 | [diff] [blame] | 822 | FORMAT = '%(asctime)-15s %(clientip)s %(user)-8s %(message)s' |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 823 | logging.basicConfig(format=FORMAT) |
| 824 | d = {'clientip': '192.168.0.1', 'user': 'fbloggs'} |
Vinay Sajip | 9a6b400 | 2010-12-14 19:40:21 +0000 | [diff] [blame] | 825 | logging.warning('Protocol problem: %s', 'connection reset', extra=d) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 826 | |
Vinay Sajip | 4039aff | 2010-09-11 10:25:28 +0000 | [diff] [blame] | 827 | would print something like:: |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 828 | |
| 829 | 2006-02-08 22:20:02,165 192.168.0.1 fbloggs Protocol problem: connection reset |
| 830 | |
| 831 | The keys in the dictionary passed in *extra* should not clash with the keys used |
| 832 | by the logging system. (See the :class:`Formatter` documentation for more |
| 833 | information on which keys are used by the logging system.) |
| 834 | |
| 835 | If you choose to use these attributes in logged messages, you need to exercise |
| 836 | some care. In the above example, for instance, the :class:`Formatter` has been |
| 837 | set up with a format string which expects 'clientip' and 'user' in the attribute |
| 838 | dictionary of the LogRecord. If these are missing, the message will not be |
| 839 | logged because a string formatting exception will occur. So in this case, you |
| 840 | always need to pass the *extra* dictionary with these keys. |
| 841 | |
| 842 | While this might be annoying, this feature is intended for use in specialized |
| 843 | circumstances, such as multi-threaded servers where the same code executes in |
| 844 | many contexts, and interesting conditions which arise are dependent on this |
| 845 | context (such as remote client IP address and authenticated user name, in the |
| 846 | above example). In such circumstances, it is likely that specialized |
| 847 | :class:`Formatter`\ s would be used with particular :class:`Handler`\ s. |
| 848 | |
Vinay Sajip | 8593ae6 | 2010-11-14 21:33:04 +0000 | [diff] [blame] | 849 | .. versionadded:: 3.2 |
| 850 | The *stack_info* parameter was added. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 851 | |
Georg Brandl | cd7f32b | 2009-06-08 09:13:45 +0000 | [diff] [blame] | 852 | .. function:: info(msg, *args, **kwargs) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 853 | |
| 854 | Logs a message with level :const:`INFO` on the root logger. The arguments are |
| 855 | interpreted as for :func:`debug`. |
| 856 | |
| 857 | |
Georg Brandl | cd7f32b | 2009-06-08 09:13:45 +0000 | [diff] [blame] | 858 | .. function:: warning(msg, *args, **kwargs) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 859 | |
| 860 | Logs a message with level :const:`WARNING` on the root logger. The arguments are |
| 861 | interpreted as for :func:`debug`. |
| 862 | |
| 863 | |
Georg Brandl | cd7f32b | 2009-06-08 09:13:45 +0000 | [diff] [blame] | 864 | .. function:: error(msg, *args, **kwargs) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 865 | |
| 866 | Logs a message with level :const:`ERROR` on the root logger. The arguments are |
| 867 | interpreted as for :func:`debug`. |
| 868 | |
| 869 | |
Georg Brandl | cd7f32b | 2009-06-08 09:13:45 +0000 | [diff] [blame] | 870 | .. function:: critical(msg, *args, **kwargs) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 871 | |
| 872 | Logs a message with level :const:`CRITICAL` on the root logger. The arguments |
| 873 | are interpreted as for :func:`debug`. |
| 874 | |
| 875 | |
Georg Brandl | cd7f32b | 2009-06-08 09:13:45 +0000 | [diff] [blame] | 876 | .. function:: exception(msg, *args) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 877 | |
| 878 | Logs a message with level :const:`ERROR` on the root logger. The arguments are |
| 879 | interpreted as for :func:`debug`. Exception info is added to the logging |
| 880 | message. This function should only be called from an exception handler. |
| 881 | |
Georg Brandl | cd7f32b | 2009-06-08 09:13:45 +0000 | [diff] [blame] | 882 | .. function:: log(level, msg, *args, **kwargs) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 883 | |
| 884 | Logs a message with level *level* on the root logger. The other arguments are |
| 885 | interpreted as for :func:`debug`. |
| 886 | |
Vinay Sajip | c8c8c69 | 2010-09-17 10:09:04 +0000 | [diff] [blame] | 887 | PLEASE NOTE: The above module-level functions which delegate to the root |
| 888 | logger should *not* be used in threads, in versions of Python earlier than |
| 889 | 2.7.1 and 3.2, unless at least one handler has been added to the root |
| 890 | logger *before* the threads are started. These convenience functions call |
| 891 | :func:`basicConfig` to ensure that at least one handler is available; in |
| 892 | earlier versions of Python, this can (under rare circumstances) lead to |
| 893 | handlers being added multiple times to the root logger, which can in turn |
| 894 | lead to multiple messages for the same event. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 895 | |
| 896 | .. function:: disable(lvl) |
| 897 | |
| 898 | Provides an overriding level *lvl* for all loggers which takes precedence over |
| 899 | the logger's own level. When the need arises to temporarily throttle logging |
Benjamin Peterson | 886af96 | 2010-03-21 23:13:07 +0000 | [diff] [blame] | 900 | output down across the whole application, this function can be useful. Its |
| 901 | effect is to disable all logging calls of severity *lvl* and below, so that |
| 902 | if you call it with a value of INFO, then all INFO and DEBUG events would be |
| 903 | discarded, whereas those of severity WARNING and above would be processed |
| 904 | according to the logger's effective level. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 905 | |
| 906 | |
| 907 | .. function:: addLevelName(lvl, levelName) |
| 908 | |
| 909 | Associates level *lvl* with text *levelName* in an internal dictionary, which is |
| 910 | used to map numeric levels to a textual representation, for example when a |
| 911 | :class:`Formatter` formats a message. This function can also be used to define |
| 912 | your own levels. The only constraints are that all levels used must be |
| 913 | registered using this function, levels should be positive integers and they |
| 914 | should increase in increasing order of severity. |
| 915 | |
Vinay Sajip | c8c8c69 | 2010-09-17 10:09:04 +0000 | [diff] [blame] | 916 | NOTE: If you are thinking of defining your own levels, please see the section |
| 917 | on :ref:`custom-levels`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 918 | |
| 919 | .. function:: getLevelName(lvl) |
| 920 | |
| 921 | Returns the textual representation of logging level *lvl*. If the level is one |
| 922 | of the predefined levels :const:`CRITICAL`, :const:`ERROR`, :const:`WARNING`, |
| 923 | :const:`INFO` or :const:`DEBUG` then you get the corresponding string. If you |
| 924 | have associated levels with names using :func:`addLevelName` then the name you |
| 925 | have associated with *lvl* is returned. If a numeric value corresponding to one |
| 926 | of the defined levels is passed in, the corresponding string representation is |
Vinay Sajip | 9a6b400 | 2010-12-14 19:40:21 +0000 | [diff] [blame] | 927 | returned. Otherwise, the string 'Level %s' % lvl is returned. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 928 | |
| 929 | |
| 930 | .. function:: makeLogRecord(attrdict) |
| 931 | |
| 932 | Creates and returns a new :class:`LogRecord` instance whose attributes are |
| 933 | defined by *attrdict*. This function is useful for taking a pickled |
| 934 | :class:`LogRecord` attribute dictionary, sent over a socket, and reconstituting |
| 935 | it as a :class:`LogRecord` instance at the receiving end. |
| 936 | |
| 937 | |
Georg Brandl | cd7f32b | 2009-06-08 09:13:45 +0000 | [diff] [blame] | 938 | .. function:: basicConfig(**kwargs) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 939 | |
| 940 | Does basic configuration for the logging system by creating a |
| 941 | :class:`StreamHandler` with a default :class:`Formatter` and adding it to the |
Vinay Sajip | cbabd7e | 2009-10-10 20:32:36 +0000 | [diff] [blame] | 942 | root logger. The functions :func:`debug`, :func:`info`, :func:`warning`, |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 943 | :func:`error` and :func:`critical` will call :func:`basicConfig` automatically |
| 944 | if no handlers are defined for the root logger. |
| 945 | |
Vinay Sajip | cbabd7e | 2009-10-10 20:32:36 +0000 | [diff] [blame] | 946 | This function does nothing if the root logger already has handlers |
| 947 | configured for it. |
| 948 | |
Vinay Sajip | c8c8c69 | 2010-09-17 10:09:04 +0000 | [diff] [blame] | 949 | PLEASE NOTE: This function should be called from the main thread |
| 950 | before other threads are started. In versions of Python prior to |
| 951 | 2.7.1 and 3.2, if this function is called from multiple threads, |
| 952 | it is possible (in rare circumstances) that a handler will be added |
| 953 | to the root logger more than once, leading to unexpected results |
| 954 | such as messages being duplicated in the log. |
| 955 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 956 | The following keyword arguments are supported. |
| 957 | |
| 958 | +--------------+---------------------------------------------+ |
| 959 | | Format | Description | |
| 960 | +==============+=============================================+ |
| 961 | | ``filename`` | Specifies that a FileHandler be created, | |
| 962 | | | using the specified filename, rather than a | |
| 963 | | | StreamHandler. | |
| 964 | +--------------+---------------------------------------------+ |
| 965 | | ``filemode`` | Specifies the mode to open the file, if | |
| 966 | | | filename is specified (if filemode is | |
| 967 | | | unspecified, it defaults to 'a'). | |
| 968 | +--------------+---------------------------------------------+ |
| 969 | | ``format`` | Use the specified format string for the | |
| 970 | | | handler. | |
| 971 | +--------------+---------------------------------------------+ |
| 972 | | ``datefmt`` | Use the specified date/time format. | |
| 973 | +--------------+---------------------------------------------+ |
Vinay Sajip | c5b2730 | 2010-10-31 14:59:16 +0000 | [diff] [blame] | 974 | | ``style`` | If ``format`` is specified, use this style | |
| 975 | | | for the format string. One of '%', '{' or | |
| 976 | | | '$' for %-formatting, :meth:`str.format` or | |
| 977 | | | :class:`string.Template` respectively, and | |
| 978 | | | defaulting to '%' if not specified. | |
| 979 | +--------------+---------------------------------------------+ |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 980 | | ``level`` | Set the root logger level to the specified | |
| 981 | | | level. | |
| 982 | +--------------+---------------------------------------------+ |
| 983 | | ``stream`` | Use the specified stream to initialize the | |
| 984 | | | StreamHandler. Note that this argument is | |
| 985 | | | incompatible with 'filename' - if both are | |
| 986 | | | present, 'stream' is ignored. | |
| 987 | +--------------+---------------------------------------------+ |
| 988 | |
Vinay Sajip | c5b2730 | 2010-10-31 14:59:16 +0000 | [diff] [blame] | 989 | .. versionchanged:: 3.2 |
| 990 | The ``style`` argument was added. |
| 991 | |
| 992 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 993 | .. function:: shutdown() |
| 994 | |
| 995 | Informs the logging system to perform an orderly shutdown by flushing and |
Christian Heimes | b186d00 | 2008-03-18 15:15:01 +0000 | [diff] [blame] | 996 | closing all handlers. This should be called at application exit and no |
| 997 | further use of the logging system should be made after this call. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 998 | |
| 999 | |
| 1000 | .. function:: setLoggerClass(klass) |
| 1001 | |
| 1002 | Tells the logging system to use the class *klass* when instantiating a logger. |
| 1003 | The class should define :meth:`__init__` such that only a name argument is |
| 1004 | required, and the :meth:`__init__` should call :meth:`Logger.__init__`. This |
| 1005 | function is typically called before any loggers are instantiated by applications |
| 1006 | which need to use custom logger behavior. |
| 1007 | |
Georg Brandl | 1eb40bc | 2010-12-03 15:30:09 +0000 | [diff] [blame] | 1008 | |
Vinay Sajip | 6156152 | 2010-12-03 11:50:38 +0000 | [diff] [blame] | 1009 | .. function:: setLogRecordFactory(factory) |
| 1010 | |
| 1011 | Set a callable which is used to create a :class:`LogRecord`. |
| 1012 | |
| 1013 | :param factory: The factory callable to be used to instantiate a log record. |
| 1014 | |
| 1015 | .. versionadded:: 3.2 |
Georg Brandl | 1eb40bc | 2010-12-03 15:30:09 +0000 | [diff] [blame] | 1016 | This function has been provided, along with :func:`getLogRecordFactory`, to |
| 1017 | allow developers more control over how the :class:`LogRecord` representing |
| 1018 | a logging event is constructed. |
Vinay Sajip | 6156152 | 2010-12-03 11:50:38 +0000 | [diff] [blame] | 1019 | |
Georg Brandl | 1eb40bc | 2010-12-03 15:30:09 +0000 | [diff] [blame] | 1020 | The factory has the following signature: |
Vinay Sajip | 6156152 | 2010-12-03 11:50:38 +0000 | [diff] [blame] | 1021 | |
Vinay Sajip | 9a6b400 | 2010-12-14 19:40:21 +0000 | [diff] [blame] | 1022 | ``factory(name, level, fn, lno, msg, args, exc_info, func=None, sinfo=None, **kwargs)`` |
Vinay Sajip | 6156152 | 2010-12-03 11:50:38 +0000 | [diff] [blame] | 1023 | |
| 1024 | :name: The logger name. |
| 1025 | :level: The logging level (numeric). |
| 1026 | :fn: The full pathname of the file where the logging call was made. |
| 1027 | :lno: The line number in the file where the logging call was made. |
| 1028 | :msg: The logging message. |
| 1029 | :args: The arguments for the logging message. |
| 1030 | :exc_info: An exception tuple, or None. |
| 1031 | :func: The name of the function or method which invoked the logging |
| 1032 | call. |
| 1033 | :sinfo: A stack traceback such as is provided by |
| 1034 | :func:`traceback.print_stack`, showing the call hierarchy. |
| 1035 | :kwargs: Additional keyword arguments. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1036 | |
Georg Brandl | 1eb40bc | 2010-12-03 15:30:09 +0000 | [diff] [blame] | 1037 | |
Benjamin Peterson | 9451a1c | 2010-03-13 22:30:34 +0000 | [diff] [blame] | 1038 | Integration with the warnings module |
| 1039 | ------------------------------------ |
| 1040 | |
| 1041 | The :func:`captureWarnings` function can be used to integrate :mod:`logging` |
| 1042 | with the :mod:`warnings` module. |
| 1043 | |
| 1044 | .. function:: captureWarnings(capture) |
| 1045 | |
| 1046 | This function is used to turn the capture of warnings by logging on and |
| 1047 | off. |
| 1048 | |
Senthil Kumaran | 46a48be | 2010-10-15 13:10:10 +0000 | [diff] [blame] | 1049 | If *capture* is ``True``, warnings issued by the :mod:`warnings` module will |
| 1050 | be redirected to the logging system. Specifically, a warning will be |
Benjamin Peterson | 9451a1c | 2010-03-13 22:30:34 +0000 | [diff] [blame] | 1051 | formatted using :func:`warnings.formatwarning` and the resulting string |
Vinay Sajip | 9a6b400 | 2010-12-14 19:40:21 +0000 | [diff] [blame] | 1052 | logged to a logger named 'py.warnings' with a severity of `WARNING`. |
Benjamin Peterson | 9451a1c | 2010-03-13 22:30:34 +0000 | [diff] [blame] | 1053 | |
Senthil Kumaran | 46a48be | 2010-10-15 13:10:10 +0000 | [diff] [blame] | 1054 | If *capture* is ``False``, the redirection of warnings to the logging system |
Benjamin Peterson | 9451a1c | 2010-03-13 22:30:34 +0000 | [diff] [blame] | 1055 | will stop, and warnings will be redirected to their original destinations |
| 1056 | (i.e. those in effect before `captureWarnings(True)` was called). |
| 1057 | |
| 1058 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 1059 | .. seealso:: |
Vinay Sajip | 7504302 | 2010-12-19 06:02:31 +0000 | [diff] [blame] | 1060 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 1061 | Module :mod:`logging.config` |
| 1062 | Configuration API for the logging module. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1063 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 1064 | Module :mod:`logging.handlers` |
| 1065 | Useful handlers included with the logging module. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1066 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 1067 | :pep:`282` - A Logging System |
| 1068 | The proposal which described this feature for inclusion in the Python standard |
| 1069 | library. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1070 | |
Vinay Sajip | c63619b | 2010-12-19 12:56:57 +0000 | [diff] [blame] | 1071 | `Original Python logging package <http://www.red-dove.com/python_logging.html>`_ |
| 1072 | This is the original source for the :mod:`logging` package. The version of the |
| 1073 | package available from this site is suitable for use with Python 1.5.2, 2.1.x |
| 1074 | and 2.2.x, which do not include the :mod:`logging` package in the standard |
| 1075 | library. |
Christian Heimes | 8b0facf | 2007-12-04 19:30:01 +0000 | [diff] [blame] | 1076 | |