15.7. logging — Logging facility for Python
Source code: Lib/logging/__init__.py
This module defines functions and classes which implement a flexible event
logging system for applications and libraries.
The key benefit of having the logging API provided by a standard library module
is that all Python modules can participate in logging, so your application log
can include your own messages integrated with messages from third-party
modules.
The module provides a lot of functionality and flexibility. If you are
unfamiliar with logging, the best way to get to grips with it is to see the
tutorials (see the links on the right).
The basic classes defined by the module, together with their functions, are
listed below.
- Loggers expose the interface that application code directly uses.
- Handlers send the log records (created by loggers) to the appropriate
destination.
- Filters provide a finer grained facility for determining which log records
to output.
- Formatters specify the layout of log records in the final output.
15.7.1. Logger Objects
Loggers have the following attributes and methods. Note that Loggers are never
instantiated directly, but always through the module-level function
logging.getLogger(name). Multiple calls to getLogger() with the same
name will always return a reference to the same Logger object.
The name is potentially a period-separated hierarchical value, like
foo.bar.baz (though it could also be just plain foo, for example).
Loggers that are further down in the hierarchical list are children of loggers
higher up in the list. For example, given a logger with a name of foo,
loggers with names of foo.bar, foo.bar.baz, and foo.bam are all
descendants of foo. The logger name hierarchy is analogous to the Python
package hierarchy, and identical to it if you organise your loggers on a
per-module basis using the recommended construction
logging.getLogger(__name__). That’s because in a module, __name__
is the module’s name in the Python package namespace.
-
class
logging.Logger
-
Logger.propagate
If this evaluates to true, events logged to this logger will be passed to the
handlers of higher level (ancestor) loggers, in addition to any handlers
attached to this logger. Messages are passed directly to the ancestor
loggers’ handlers - neither the level nor filters of the ancestor loggers in
question are considered.
If this evaluates to false, logging messages are not passed to the handlers
of ancestor loggers.
The constructor sets this attribute to True.
Note
If you attach a handler to a logger and one or more of its
ancestors, it may emit the same record multiple times. In general, you
should not need to attach a handler to more than one logger - if you just
attach it to the appropriate logger which is highest in the logger
hierarchy, then it will see all events logged by all descendant loggers,
provided that their propagate setting is left set to True. A common
scenario is to attach handlers only to the root logger, and to let
propagation take care of the rest.
-
Logger.setLevel(level)
Sets the threshold for this logger to level. Logging messages which are less
severe than level will be ignored. When a logger is created, the level is set to
NOTSET (which causes all messages to be processed when the logger is
the root logger, or delegation to the parent when the logger is a non-root
logger). Note that the root logger is created with level WARNING.
The term ‘delegation to the parent’ means that if a logger has a level of
NOTSET, its chain of ancestor loggers is traversed until either an ancestor with
a level other than NOTSET is found, or the root is reached.
If an ancestor is found with a level other than NOTSET, then that ancestor’s
level is treated as the effective level of the logger where the ancestor search
began, and is used to determine how a logging event is handled.
If the root is reached, and it has a level of NOTSET, then all messages will be
processed. Otherwise, the root’s level will be used as the effective level.
See Logging Levels for a list of levels.
-
Logger.isEnabledFor(lvl)
Indicates if a message of severity lvl would be processed by this logger.
This method checks first the module-level level set by
logging.disable(lvl) and then the logger’s effective level as determined
by getEffectiveLevel().
-
Logger.getEffectiveLevel()
Indicates the effective level for this logger. If a value other than
NOTSET has been set using setLevel(), it is returned. Otherwise,
the hierarchy is traversed towards the root until a value other than
NOTSET is found, and that value is returned. The value returned is
an integer, typically one of logging.DEBUG, logging.INFO
etc.
-
Logger.getChild(suffix)
Returns a logger which is a descendant to this logger, as determined by the suffix.
Thus, logging.getLogger('abc').getChild('def.ghi') would return the same
logger as would be returned by logging.getLogger('abc.def.ghi'). This is a
convenience method, useful when the parent logger is named using e.g. __name__
rather than a literal string.
-
Logger.debug(msg, *args, **kwargs)
Logs a message with level DEBUG on this logger. The msg is the
message format string, and the args are the arguments which are merged into
msg using the string formatting operator. (Note that this means that you can
use keywords in the format string, together with a single dictionary argument.)
There are two keyword arguments in kwargs which are inspected: exc_info
which, if it does not evaluate as false, causes exception information to be
added to the logging message. If an exception tuple (in the format returned by
sys.exc_info()) is provided, it is used; otherwise, sys.exc_info()
is called to get the exception information.
The second keyword argument is extra which can be used to pass a
dictionary which is used to populate the __dict__ of the LogRecord created for
the logging event with user-defined attributes. These custom attributes can then
be used as you like. For example, they could be incorporated into logged
messages. For example:
FORMAT = '%(asctime)-15s %(clientip)s %(user)-8s %(message)s'
logging.basicConfig(format=FORMAT)
d = {'clientip': '192.168.0.1', 'user': 'fbloggs'}
logger = logging.getLogger('tcpserver')
logger.warning('Protocol problem: %s', 'connection reset', extra=d)
would print something like
2006-02-08 22:20:02,165 192.168.0.1 fbloggs Protocol problem: connection reset
The keys in the dictionary passed in extra should not clash with the keys used
by the logging system. (See the Formatter documentation for more
information on which keys are used by the logging system.)
If you choose to use these attributes in logged messages, you need to exercise
some care. In the above example, for instance, the Formatter has been
set up with a format string which expects ‘clientip’ and ‘user’ in the attribute
dictionary of the LogRecord. If these are missing, the message will not be
logged because a string formatting exception will occur. So in this case, you
always need to pass the extra dictionary with these keys.
While this might be annoying, this feature is intended for use in specialized
circumstances, such as multi-threaded servers where the same code executes in
many contexts, and interesting conditions which arise are dependent on this
context (such as remote client IP address and authenticated user name, in the
above example). In such circumstances, it is likely that specialized
Formatters would be used with particular Handlers.
-
Logger.info(msg, *args, **kwargs)
Logs a message with level INFO on this logger. The arguments are
interpreted as for debug().
-
Logger.warning(msg, *args, **kwargs)
Logs a message with level WARNING on this logger. The arguments are
interpreted as for debug().
-
Logger.error(msg, *args, **kwargs)
Logs a message with level ERROR on this logger. The arguments are
interpreted as for debug().
-
Logger.critical(msg, *args, **kwargs)
Logs a message with level CRITICAL on this logger. The arguments are
interpreted as for debug().
-
Logger.log(lvl, msg, *args, **kwargs)
Logs a message with integer level lvl on this logger. The other arguments are
interpreted as for debug().
-
Logger.exception(msg, *args, **kwargs)
Logs a message with level ERROR on this logger. The arguments are
interpreted as for debug(), except that any passed exc_info is not
inspected. Exception info is always added to the logging message. This method
should only be called from an exception handler.
-
Logger.addFilter(filter)
Adds the specified filter filter to this logger.
-
Logger.removeFilter(filter)
Removes the specified filter filter from this logger.
-
Logger.filter(record)
Applies this logger’s filters to the record and returns a true value if the
record is to be processed. The filters are consulted in turn, until one of
them returns a false value. If none of them return a false value, the record
will be processed (passed to handlers). If one returns a false value, no
further processing of the record occurs.
-
Logger.addHandler(hdlr)
Adds the specified handler hdlr to this logger.
-
Logger.removeHandler(hdlr)
Removes the specified handler hdlr from this logger.
-
Logger.findCaller()
Finds the caller’s source filename and line number. Returns the filename, line
number and function name as a 3-element tuple.
Changed in version 2.4: The function name was added. In earlier versions, the filename and line
number were returned as a 2-element tuple.
-
Logger.handle(record)
Handles a record by passing it to all handlers associated with this logger and
its ancestors (until a false value of propagate is found). This method is used
for unpickled records received from a socket, as well as those created locally.
Logger-level filtering is applied using filter().
-
Logger.makeRecord(name, lvl, fn, lno, msg, args, exc_info, func=None, extra=None)
This is a factory method which can be overridden in subclasses to create
specialized LogRecord instances.
Changed in version 2.5: func and extra were added.
15.7.2. Logging Levels
The numeric values of logging levels are given in the following table. These are
primarily of interest if you want to define your own levels, and need them to
have specific values relative to the predefined levels. If you define a level
with the same numeric value, it overwrites the predefined value; the predefined
name is lost.
| Level |
Numeric value |
CRITICAL |
50 |
ERROR |
40 |
WARNING |
30 |
INFO |
20 |
DEBUG |
10 |
NOTSET |
0 |
15.7.3. Handler Objects
Handlers have the following attributes and methods. Note that Handler
is never instantiated directly; this class acts as a base for more useful
subclasses. However, the __init__() method in subclasses needs to call
Handler.__init__().
-
Handler.__init__(level=NOTSET)
Initializes the Handler instance by setting its level, setting the list
of filters to the empty list and creating a lock (using createLock()) for
serializing access to an I/O mechanism.
-
Handler.createLock()
Initializes a thread lock which can be used to serialize access to underlying
I/O functionality which may not be threadsafe.
-
Handler.acquire()
Acquires the thread lock created with createLock().
-
Handler.release()
Releases the thread lock acquired with acquire().
-
Handler.setLevel(level)
Sets the threshold for this handler to level. Logging messages which are less
severe than level will be ignored. When a handler is created, the level is set
to NOTSET (which causes all messages to be processed).
See Logging Levels for a list of levels.
-
Handler.setFormatter(fmt)
Sets the Formatter for this handler to fmt.
-
Handler.addFilter(filter)
Adds the specified filter filter to this handler.
-
Handler.removeFilter(filter)
Removes the specified filter filter from this handler.
-
Handler.filter(record)
Applies this handler’s filters to the record and returns a true value if the
record is to be processed. The filters are consulted in turn, until one of
them returns a false value. If none of them return a false value, the record
will be emitted. If one returns a false value, the handler will not emit the
record.
-
Handler.flush()
Ensure all logging output has been flushed. This version does nothing and is
intended to be implemented by subclasses.
-
Handler.close()
Tidy up any resources used by the handler. This version does no output but
removes the handler from an internal list of handlers which is closed when
shutdown() is called. Subclasses should ensure that this gets called
from overridden close() methods.
-
Handler.handle(record)
Conditionally emits the specified logging record, depending on filters which may
have been added to the handler. Wraps the actual emission of the record with
acquisition/release of the I/O thread lock.
-
Handler.handleError(record)
This method should be called from handlers when an exception is encountered
during an emit() call. If the module-level attribute
raiseExceptions is False, exceptions get silently ignored. This is
what is mostly wanted for a logging system - most users will not care about
errors in the logging system, they are more interested in application
errors. You could, however, replace this with a custom handler if you wish.
The specified record is the one which was being processed when the exception
occurred. (The default value of raiseExceptions is True, as that is
more useful during development).
-
Handler.format(record)
Do formatting for a record - if a formatter is set, use it. Otherwise, use the
default formatter for the module.
-
Handler.emit(record)
Do whatever it takes to actually log the specified logging record. This version
is intended to be implemented by subclasses and so raises a
NotImplementedError.
For a list of handlers included as standard, see logging.handlers.
15.7.5. Filter Objects
Filters can be used by Handlers and Loggers for more sophisticated
filtering than is provided by levels. The base filter class only allows events
which are below a certain point in the logger hierarchy. For example, a filter
initialized with ‘A.B’ will allow events logged by loggers ‘A.B’, ‘A.B.C’,
‘A.B.C.D’, ‘A.B.D’ etc. but not ‘A.BB’, ‘B.A.B’ etc. If initialized with the
empty string, all events are passed.
-
class
logging.Filter(name='')
Returns an instance of the Filter class. If name is specified, it
names a logger which, together with its children, will have its events allowed
through the filter. If name is the empty string, allows every event.
-
filter(record)
Is the specified record to be logged? Returns zero for no, nonzero for
yes. If deemed appropriate, the record may be modified in-place by this
method.
Note that filters attached to handlers are consulted before an event is
emitted by the handler, whereas filters attached to loggers are consulted
whenever an event is logged (using debug(), info(),
etc.), before sending an event to handlers. This means that events which have
been generated by descendant loggers will not be filtered by a logger’s filter
setting, unless the filter has also been applied to those descendant loggers.
You don’t actually need to subclass Filter: you can pass any instance
which has a filter method with the same semantics.
Although filters are used primarily to filter records based on more
sophisticated criteria than levels, they get to see every record which is
processed by the handler or logger they’re attached to: this can be useful if
you want to do things like counting how many records were processed by a
particular logger or handler, or adding, changing or removing attributes in
the LogRecord being processed. Obviously changing the LogRecord needs to be
done with some care, but it does allow the injection of contextual information
into logs (see Using Filters to impart contextual information).
15.7.6. LogRecord Objects
LogRecord instances are created automatically by the Logger
every time something is logged, and can be created manually via
makeLogRecord() (for example, from a pickled event received over the
wire).
-
class
logging.LogRecord(name, level, pathname, lineno, msg, args, exc_info, func=None)
Contains all the information pertinent to the event being logged.
The primary information is passed in msg and args, which
are combined using msg % args to create the message field of the
record.
| Parameters: |
- name – The name of the logger used to log the event represented by
this LogRecord. Note that this name will always have this
value, even though it may be emitted by a handler attached to
a different (ancestor) logger.
- level – The numeric level of the logging event (one of DEBUG, INFO etc.)
Note that this is converted to two attributes of the LogRecord:
levelno for the numeric value and levelname for the
corresponding level name.
- pathname – The full pathname of the source file where the logging call
was made.
- lineno – The line number in the source file where the logging call was
made.
- msg – The event description message, possibly a format string with
placeholders for variable data.
- args – Variable data to merge into the msg argument to obtain the
event description.
- exc_info – An exception tuple with the current exception information,
or
None if no exception information is available.
- func – The name of the function or method from which the logging call
was invoked.
|
Changed in version 2.5: func was added.
-
getMessage()
Returns the message for this LogRecord instance after merging any
user-supplied arguments with the message. If the user-supplied message
argument to the logging call is not a string, str() is called on it to
convert it to a string. This allows use of user-defined classes as
messages, whose __str__ method can return the actual format string to
be used.
15.7.7. LogRecord attributes
The LogRecord has a number of attributes, most of which are derived from the
parameters to the constructor. (Note that the names do not always correspond
exactly between the LogRecord constructor parameters and the LogRecord
attributes.) These attributes can be used to merge data from the record into
the format string. The following table lists (in alphabetical order) the
attribute names, their meanings and the corresponding placeholder in a %-style
format string.
| Attribute name |
Format |
Description |
| args |
You shouldn’t need to
format this yourself. |
The tuple of arguments merged into msg to
produce message, or a dict whose values
are used for the merge (when there is only one
argument, and it is a dictionary). |
| asctime |
%(asctime)s |
Human-readable time when the
LogRecord was created. By default
this is of the form ‘2003-07-08 16:49:45,896’
(the numbers after the comma are millisecond
portion of the time). |
| created |
%(created)f |
Time when the LogRecord was created
(as returned by time.time()). |
| exc_info |
You shouldn’t need to
format this yourself. |
Exception tuple (à la sys.exc_info) or,
if no exception has occurred, None. |
| filename |
%(filename)s |
Filename portion of pathname. |
| funcName |
%(funcName)s |
Name of function containing the logging call. |
| levelname |
%(levelname)s |
Text logging level for the message
('DEBUG', 'INFO', 'WARNING',
'ERROR', 'CRITICAL'). |
| levelno |
%(levelno)s |
Numeric logging level for the message
(DEBUG, INFO,
WARNING, ERROR,
CRITICAL). |
| lineno |
%(lineno)d |
Source line number where the logging call was
issued (if available). |
| module |
%(module)s |
Module (name portion of filename). |
| msecs |
%(msecs)d |
Millisecond portion of the time when the
LogRecord was created. |
| message |
%(message)s |
The logged message, computed as msg %
args. This is set when
Formatter.format() is invoked. |
| msg |
You shouldn’t need to
format this yourself. |
The format string passed in the original
logging call. Merged with args to
produce message, or an arbitrary object
(see Using arbitrary objects as messages). |
| name |
%(name)s |
Name of the logger used to log the call. |
| pathname |
%(pathname)s |
Full pathname of the source file where the
logging call was issued (if available). |
| process |
%(process)d |
Process ID (if available). |
| processName |
%(processName)s |
Process name (if available). |
| relativeCreated |
%(relativeCreated)d |
Time in milliseconds when the LogRecord was
created, relative to the time the logging
module was loaded. |
| thread |
%(thread)d |
Thread ID (if available). |
| threadName |
%(threadName)s |
Thread name (if available). |
Changed in version 2.5: funcName was added.
Changed in version 2.6: processName was added.
15.7.8. LoggerAdapter Objects
LoggerAdapter instances are used to conveniently pass contextual
information into logging calls. For a usage example, see the section on
adding contextual information to your logging output.
-
class
logging.LoggerAdapter(logger, extra)
Returns an instance of LoggerAdapter initialized with an
underlying Logger instance and a dict-like object.
-
process(msg, kwargs)
Modifies the message and/or keyword arguments passed to a logging call in
order to insert contextual information. This implementation takes the object
passed as extra to the constructor and adds it to kwargs using key
‘extra’. The return value is a (msg, kwargs) tuple which has the
(possibly modified) versions of the arguments passed in.
In addition to the above, LoggerAdapter supports the following
methods of Logger: debug(), info(),
warning(), error(), exception(),
critical(), log() and isEnabledFor().
These methods have the same signatures as their counterparts in Logger,
so you can use the two types of instances interchangeably for these calls.
15.7.9. Thread Safety
The logging module is intended to be thread-safe without any special work
needing to be done by its clients. It achieves this though using threading
locks; there is one lock to serialize access to the module’s shared data, and
each handler also creates a lock to serialize access to its underlying I/O.
If you are implementing asynchronous signal handlers using the signal
module, you may not be able to use logging from within such handlers. This is
because lock implementations in the threading module are not always
re-entrant, and so cannot be invoked from such signal handlers.
15.7.10. Module-Level Functions
In addition to the classes described above, there are a number of module- level
functions.
-
logging.getLogger([name])
Return a logger with the specified name or, if no name is specified, return a
logger which is the root logger of the hierarchy. If specified, the name is
typically a dot-separated hierarchical name like “a”, “a.b” or “a.b.c.d”.
Choice of these names is entirely up to the developer who is using logging.
All calls to this function with a given name return the same logger instance.
This means that logger instances never need to be passed between different parts
of an application.
-
logging.getLoggerClass()
Return either the standard Logger class, or the last class passed to
setLoggerClass(). This function may be called from within a new class
definition, to ensure that installing a customized Logger class will
not undo customizations already applied by other code. For example:
class MyLogger(logging.getLoggerClass()):
# ... override behaviour here
-
logging.debug(msg[, *args[, **kwargs]])
Logs a message with level DEBUG on the root logger. The msg is the
message format string, and the args are the arguments which are merged into
msg using the string formatting operator. (Note that this means that you can
use keywords in the format string, together with a single dictionary argument.)
There are two keyword arguments in kwargs which are inspected: exc_info
which, if it does not evaluate as false, causes exception information to be
added to the logging message. If an exception tuple (in the format returned by
sys.exc_info()) is provided, it is used; otherwise, sys.exc_info()
is called to get the exception information.
The other optional keyword argument is extra which can be used to pass a
dictionary which is used to populate the __dict__ of the LogRecord created for
the logging event with user-defined attributes. These custom attributes can then
be used as you like. For example, they could be incorporated into logged
messages. For example:
FORMAT = "%(asctime)-15s %(clientip)s %(user)-8s %(message)s"
logging.basicConfig(format=FORMAT)
d = {'clientip': '192.168.0.1', 'user': 'fbloggs'}
logging.warning("Protocol problem: %s", "connection reset", extra=d)
would print something like:
2006-02-08 22:20:02,165 192.168.0.1 fbloggs Protocol problem: connection reset
The keys in the dictionary passed in extra should not clash with the keys used
by the logging system. (See the Formatter documentation for more
information on which keys are used by the logging system.)
If you choose to use these attributes in logged messages, you need to exercise
some care. In the above example, for instance, the Formatter has been
set up with a format string which expects ‘clientip’ and ‘user’ in the attribute
dictionary of the LogRecord. If these are missing, the message will not be
logged because a string formatting exception will occur. So in this case, you
always need to pass the extra dictionary with these keys.
While this might be annoying, this feature is intended for use in specialized
circumstances, such as multi-threaded servers where the same code executes in
many contexts, and interesting conditions which arise are dependent on this
context (such as remote client IP address and authenticated user name, in the
above example). In such circumstances, it is likely that specialized
Formatters would be used with particular Handlers.
Changed in version 2.5: extra was added.
-
logging.info(msg[, *args[, **kwargs]])
Logs a message with level INFO on the root logger. The arguments are
interpreted as for debug().
-
logging.warning(msg[, *args[, **kwargs]])
Logs a message with level WARNING on the root logger. The arguments are
interpreted as for debug().
-
logging.error(msg[, *args[, **kwargs]])
Logs a message with level ERROR on the root logger. The arguments are
interpreted as for debug().
-
logging.critical(msg[, *args[, **kwargs]])
Logs a message with level CRITICAL on the root logger. The arguments
are interpreted as for debug().
-
logging.exception(msg[, *args[, **kwargs]])
Logs a message with level ERROR on the root logger. The arguments are
interpreted as for debug(), except that any passed exc_info is not
inspected. Exception info is always added to the logging message. This
function should only be called from an exception handler.
-
logging.log(level, msg[, *args[, **kwargs]])
Logs a message with level level on the root logger. The other arguments are
interpreted as for debug().
Note
The above module-level convenience functions, which delegate to the
root logger, call basicConfig() to ensure that at least one handler
is available. Because of this, they should not be used in threads,
in versions of Python earlier than 2.7.1 and 3.2, unless at least one
handler has been added to the root logger before the threads are
started. In earlier versions of Python, due to a thread safety shortcoming
in basicConfig(), this can (under rare circumstances) lead to
handlers being added multiple times to the root logger, which can in turn
lead to multiple messages for the same event.
-
logging.disable(lvl)
Provides an overriding level lvl for all loggers which takes precedence over
the logger’s own level. When the need arises to temporarily throttle logging
output down across the whole application, this function can be useful. Its
effect is to disable all logging calls of severity lvl and below, so that
if you call it with a value of INFO, then all INFO and DEBUG events would be
discarded, whereas those of severity WARNING and above would be processed
according to the logger’s effective level. If
logging.disable(logging.NOTSET) is called, it effectively removes this
overriding level, so that logging output again depends on the effective
levels of individual loggers.
-
logging.addLevelName(lvl, levelName)
Associates level lvl with text levelName in an internal dictionary, which is
used to map numeric levels to a textual representation, for example when a
Formatter formats a message. This function can also be used to define
your own levels. The only constraints are that all levels used must be
registered using this function, levels should be positive integers and they
should increase in increasing order of severity.
Note
If you are thinking of defining your own levels, please see the
section on Custom Levels.
-
logging.getLevelName(lvl)
Returns the textual representation of logging level lvl. If the level is one
of the predefined levels CRITICAL, ERROR, WARNING,
INFO or DEBUG then you get the corresponding string. If you
have associated levels with names using addLevelName() then the name you
have associated with lvl is returned. If a numeric value corresponding to one
of the defined levels is passed in, the corresponding string representation is
returned. Otherwise, the string “Level %s” % lvl is returned.
Note
Integer levels should be used when e.g. setting levels on instances
of Logger and handlers. This function is used to convert between
an integer level and the level name displayed in the formatted log output
by means of the %(levelname)s format specifier (see
LogRecord attributes).
-
logging.makeLogRecord(attrdict)
Creates and returns a new LogRecord instance whose attributes are
defined by attrdict. This function is useful for taking a pickled
LogRecord attribute dictionary, sent over a socket, and reconstituting
it as a LogRecord instance at the receiving end.
-
logging.basicConfig([**kwargs])
Does basic configuration for the logging system by creating a
StreamHandler with a default Formatter and adding it to the
root logger. The functions debug(), info(), warning(),
error() and critical() will call basicConfig() automatically
if no handlers are defined for the root logger.
This function does nothing if the root logger already has handlers
configured for it.
Changed in version 2.4: Formerly, basicConfig() did not take any keyword arguments.
Note
This function should be called from the main thread before other
threads are started. In versions of Python prior to 2.7.1 and 3.2, if
this function is called from multiple threads, it is possible (in rare
circumstances) that a handler will be added to the root logger more than
once, leading to unexpected results such as messages being duplicated in
the log.
The following keyword arguments are supported.
| Format |
Description |
| filename |
Specifies that a FileHandler be created,
using the specified filename, rather than a
StreamHandler. |
| filemode |
If filename is specified, open the file
in this mode. Defaults to 'a'. |
| format |
Use the specified format string for the
handler. |
| datefmt |
Use the specified date/time format, as
accepted by time.strftime(). |
| level |
Set the root logger level to the specified
level. |
| stream |
Use the specified stream to initialize the
StreamHandler. Note that this argument is
incompatible with filename - if both are
present, stream is ignored. |
-
logging.shutdown()
Informs the logging system to perform an orderly shutdown by flushing and
closing all handlers. This should be called at application exit and no
further use of the logging system should be made after this call.
-
logging.setLoggerClass(klass)
Tells the logging system to use the class klass when instantiating a logger.
The class should define __init__() such that only a name argument is
required, and the __init__() should call Logger.__init__(). This
function is typically called before any loggers are instantiated by applications
which need to use custom logger behavior.
15.7.11. Integration with the warnings module
The captureWarnings() function can be used to integrate logging
with the warnings module.
-
logging.captureWarnings(capture)
This function is used to turn the capture of warnings by logging on and
off.
If capture is True, warnings issued by the warnings module will
be redirected to the logging system. Specifically, a warning will be
formatted using warnings.formatwarning() and the resulting string
logged to a logger named 'py.warnings' with a severity of WARNING.
If capture is False, the redirection of warnings to the logging system
will stop, and warnings will be redirected to their original destinations
(i.e. those in effect before captureWarnings(True) was called).
See also
- Module
logging.config
- Configuration API for the logging module.
- Module
logging.handlers
- Useful handlers included with the logging module.
- PEP 282 - A Logging System
- The proposal which described this feature for inclusion in the Python standard
library.
- Original Python logging package
- This is the original source for the
logging package. The version of the
package available from this site is suitable for use with Python 1.5.2, 2.1.x
and 2.2.x, which do not include the logging package in the standard
library.