内容表

logging — Python 日志设施

上一话题

getopt — 命令行选项 C 样式剖析器

下一话题

`logging` — Python 日志设施 ¶

源代码： Lib/logging/__init__.py

此模块为应用程序和库实现灵活事件日志系统，定义了一些函数和类。

由标准库模块提供日志 API 的关键好处是，所有 Python 模块都可以参与日志记录，因此，应用程序日志可以包括自己集成来自第 3 方模块消息的消息。

Here’s a simple example of idiomatic usage:

# myapp.py
import logging
import mylib
logger = logging.getLogger(__name__)
def main():
    logging.basicConfig(filename='myapp.log', level=logging.INFO)
    logger.info('Started')
    mylib.do_something()
    logger.info('Finished')
if __name__ == '__main__':
    main()

# mylib.py
import logging
logger = logging.getLogger(__name__)
def do_something():
    logger.info('Doing something')

If you run myapp.py , you should see this in myapp.log :

INFO:__main__:Started
INFO:mylib:Doing something
INFO:__main__:Finished

The key feature of this idiomatic usage is that the majority of code is simply creating a module level logger with getLogger(__name__) , and using that logger to do any needed logging. This is concise, while allowing downstream code fine-grained control if needed. Logged messages to the module-level logger get forwarded to handlers of loggers in higher-level modules, all the way up to the highest-level logger known as the root logger; this approach is known as hierarchical logging.

For logging to be useful, it needs to be configured: setting the levels and destinations for each logger, potentially changing how specific modules log, often based on command-line arguments or application configuration. In most cases, like the one above, only the root logger needs to be so configured, since all the lower level loggers at module level eventually forward their messages to its handlers. basicConfig() provides a quick way to configure the root logger that handles many use cases.

模块提供了许多功能和灵活性。若不熟悉日志记录，掌握它的最佳方式是查看教程 ( 见上文和右边的链接 ).

The basic classes defined by the module, together with their attributes and methods, are listed in the sections below.

日志器暴露应用程序代码，可以直接使用的接口。
处理程序将日志记录 (由日志器所创建) 发送到适当目的地。
过滤器为确定要输出哪些日志，提供更细粒度设施。
格式化程序指定最终输出日志记录的布局。

日志器对象 ¶

日志器拥有下列属性和方法。注意，日志器应该 NEVER 被直接实例化，但始终透过模块级函数 logging.getLogger(name) 。多次调用 getLogger() 采用相同名称将始终返回同一 Logger 对象的引用。

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 ，和 foo.bam are all descendants of foo . In addition, all loggers are descendants of the root logger. 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 ¶

name ¶

This is the logger’s name, and is the value that was passed to getLogger() to obtain the logger.

注意

This attribute should be treated as read-only.

level ¶

The threshold of this logger, as set by the setLevel() 方法。

注意

Do not set this attribute directly - always use setLevel() , which has checks for the level passed to it.

parent ¶

The parent logger of this logger. It may change based on later instantiation of loggers which are higher up in the namespace hierarchy.

注意

This value should be treated as read-only.

propagate ¶

If this attribute 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.

Spelling it out with an example: If the propagate attribute of the logger named A.B.C evaluates to true, any event logged to A.B.C via a method call such as logging.getLogger('A.B.C').error(...) will [subject to passing that logger’s level and filter settings] be passed in turn to any handlers attached to loggers named A.B , A and the root logger, after first being passed to any handlers attached to A.B.C . If any logger in the chain A.B.C , A.B , A 有它自己的 propagate attribute set to false, then that is the last logger whose handlers are offered the event to handle, and propagation stops at that point.

The constructor sets this attribute to True .

注意

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.

handlers ¶

The list of handlers directly attached to this logger instance.

注意

This attribute should be treated as read-only; it is normally changed via the addHandler() and removeHandler() methods, which use locks to ensure thread-safe operation.

被禁用 ¶

This attribute disables handling of any events. It is set to False in the initializer, and only changed by logging configuration code.

注意

This attribute should be treated as read-only.

setLevel ( level ) ¶

将此日志器的阈值设为 level 。日志消息级别小于 level 会被忽略；日志消息拥有严重 level 或更高将由服务此日志器的任何一个或多个处理程序发出，除非处理程序级别已被设为严重级别高于 level .

当创建时，日志器级别被设为 NOTSET (导致处理所有消息当日志器是根日志器时，或委托给父级当日志器是非根日志器时)。注意，根日志器的创建是采用级别 WARNING .

术语 "委托给父级" 意味着，若日志器拥有 NOTSET 级别，将遍历其祖先日志器链，直到找到非 NOTSET 级别的祖先为止，或到达根。

若找到的祖先级别不是 NOTSET，那么，该祖先的级别被视为开始祖先搜索日志器的有效级别，并用于确定如何处理 logging 事件。

若到达根，且其拥有 NOTSET 级别，那么将处理所有消息。否则，将根级别用作有效级别。

见日志级别了解级别列表。

3.2 版改变： The level parameter now accepts a string representation of the level such as ‘INFO’ as an alternative to the integer constants such as INFO . Note, however, that levels are internally stored as integers, and methods such as e.g. getEffectiveLevel() and isEnabledFor() will return/expect to be passed integers.

isEnabledFor ( level ) ¶: Indicates if a message of severity level would be processed by this logger. This method checks first the module-level level set by logging.disable(level) and then the logger’s effective level as determined by getEffectiveLevel() .

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.

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.

Added in version 3.2.

getChildren ( ) ¶

Returns a set of loggers which are immediate children of this logger. So for example logging.getLogger().getChildren() might return a set containing loggers named foo and bar , but a logger named foo.bar wouldn’t be included in the set. Likewise, logging.getLogger('foo').getChildren() might return a set including a logger named foo.bar , but it wouldn’t include one named foo.bar.baz .

3.12 版添加。

debug ( msg , * args , ** kwargs ) ¶

日志消息采用级别 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.) No % formatting operation is performed on msg when no args are supplied.

There are four keyword arguments in kwargs which are inspected: exc_info , stack_info , stacklevel and extra .

若 exc_info does not evaluate as false, it causes exception information to be added to the logging message. If an exception tuple (in the format returned by sys.exc_info() ) or an exception instance is provided, it is used; otherwise, sys.exc_info() is called to get the exception information.

The second optional keyword argument is stack_info ，其默认为 False . If true, stack information is added to the logging message, including the actual logging call. Note that this is not the same stack information as that displayed through specifying exc_info : The former is stack frames from the bottom of the stack up to the logging call in the current thread, whereas the latter is information about stack frames which have been unwound, following an exception, while searching for exception handlers.

You can specify stack_info independently of exc_info , e.g. to just show how you got to a certain point in your code, even when no exceptions were raised. The stack frames are printed following a header line which says:

Stack (most recent call last):

This mimics the Traceback (most recent call last): which is used when displaying exception frames.

The third optional keyword argument is stacklevel ，其默认为 1 . If greater than 1, the corresponding number of stack frames are skipped when computing the line number and function name set in the LogRecord created for the logging event. This can be used in logging helpers so that the function name, filename and line number recorded are not the information for the helper function/method, but rather its caller. The name of this parameter mirrors the equivalent one in the warnings 模块。

The fourth 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)s %(clientip)-15s %(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 section on LogRecord 属性 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 Formatter s would be used with particular Handler 。

If no handler is attached to this logger (or any of its ancestors, taking into account the relevant Logger.propagate attributes), the message will be sent to the handler set on lastResort .

3.2 版改变： The stack_info 参数被添加。

3.5 版改变： The exc_info 参数现在可以接受异常实例。

3.8 版改变： The stacklevel 参数被添加。

info ( msg , * args , ** kwargs ) ¶: 日志消息采用级别 INFO 在此日志器。自变量的解释如 debug() .

warning ( msg , * args , ** kwargs ) ¶

日志消息采用级别 WARNING 在此日志器。自变量的解释如 debug() .

注意

存在过时方法 warn 功能等同于 warning . As warn 被弃用，请不要使用它 - 使用 warning 代替。

error ( msg , * args , ** kwargs ) ¶: 日志消息采用级别 ERROR 在此日志器。自变量的解释如 debug() .

critical ( msg , * args , ** kwargs ) ¶: 日志消息采用级别 CRITICAL 在此日志器。自变量的解释如 debug() .

log ( level , msg , * args , ** kwargs ) ¶: 日志消息采用整数级别 level 在此日志器。其它自变量的解释如 debug() .

exception ( msg , * args , ** kwargs ) ¶: 日志消息采用级别 ERROR 在此日志器。自变量的解释如 debug() . Exception info is added to the logging message. This method should only be called from an exception handler.

addFilter ( filter ) ¶: 添加指定过滤器 filter 到此日志器。

removeFilter ( filter ) ¶: 移除指定过滤器 filter 从此日志器。

filter ( record ) ¶: Apply this logger’s filters to the record and return True 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.

addHandler ( hdlr ) ¶: 添加指定处理程序 hdlr 到此日志器。

removeHandler ( hdlr ) ¶: 移除指定处理程序 hdlr 从此日志器。

findCaller ( stack_info = False , stacklevel = 1 ) ¶

Finds the caller’s source filename and line number. Returns the filename, line number, function name and stack information as a 4-element tuple. The stack information is returned as None unless stack_info is True .

The stacklevel parameter is passed from code calling the debug() and other APIs. If greater than 1, the excess is used to skip stack frames before determining the values to be returned. This will generally be useful when calling logging APIs from helper/wrapper code, so that the information in the event log refers not to the helper/wrapper code, but to the code that calls it.

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() .

makeRecord ( name , level , fn , lno , msg , args , exc_info , func = None , extra = None , sinfo = None ) ¶: This is a factory method which can be overridden in subclasses to create specialized LogRecord 实例。

hasHandlers ( ) ¶

Checks to see if this logger has any handlers configured. This is done by looking for handlers in this logger and its parents in the logger hierarchy. Returns True if a handler was found, else False . The method stops searching up the hierarchy whenever a logger with the ‘propagate’ attribute set to false is found - that will be the last logger which is checked for the existence of handlers.

Added in version 3.2.

3.7 版改变：日志器现在可以被腌制和取消腌制。

日志级别 ¶

下表给出了 logging 级别的数值。这些是首要感兴趣的，若想定义自己的级别，且需要它们拥有相对于预定义级别的特定值。若采用相同数值定义级别，它会覆盖预定义值；预定义名称丢失。

级别	数值	What it means / When to use it
logging. NOTSET ¶	0	When set on a logger, indicates that ancestor loggers are to be consulted to determine the effective level. If that still resolves to `NOTSET` , then all events are logged. When set on a handler, all events are handled.
logging. DEBUG ¶	10	Detailed information, typically only of interest to a developer trying to diagnose a problem.
logging. INFO ¶	20	Confirmation that things are working as expected.
logging. WARNING ¶	30	An indication that something unexpected happened, or that a problem might occur in the near future (e.g. ‘disk space low’). The software is still working as expected.
logging. ERROR ¶	40	Due to a more serious problem, the software has not been able to perform some function.
logging. CRITICAL ¶	50	A serious error, indicating that the program itself may be unable to continue running.

处理程序对象 ¶

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__() .

class logging. Handler ¶

__init__ ( level = NOTSET ) ¶: 初始化 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.

createLock ( ) ¶: Initializes a thread lock which can be used to serialize access to underlying I/O functionality which may not be threadsafe.

acquire ( ) ¶: 获得的线程锁创建采用 createLock() .

release ( ) ¶: Releases the thread lock acquired with acquire() .

setLevel ( level ) ¶

Sets the threshold for this handler to level 。日志消息级别小于 level will be ignored. When a handler is created, the level is set to NOTSET (which causes all messages to be processed).

见日志级别了解级别列表。

3.2 版改变： The level parameter now accepts a string representation of the level such as ‘INFO’ as an alternative to the integer constants such as INFO .

setFormatter ( fmt ) ¶: 设置 Formatter 为此处理程序到 fmt .

addFilter ( filter ) ¶: 添加指定过滤器 filter 到此处理程序。

removeFilter ( filter ) ¶: 移除指定过滤器 filter 从此处理程序。

filter ( record ) ¶: Apply this handler’s filters to the record and return True 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.

flush ( ) ¶: Ensure all logging output has been flushed. This version does nothing and is intended to be implemented by subclasses.

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() 方法。

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.

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).

format ( record ) ¶: Do formatting for a record - if a formatter is set, use it. Otherwise, use the default formatter for the module.

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 .

警告

This method is called after a handler-level lock is acquired, which is released after this method returns. When you override this method, note that you should be careful when calling anything that invokes other parts of the logging API which might do locking, because that might result in a deadlock. Specifically:

Logging configuration APIs acquire the module-level lock, and then individual handler-level locks as those handlers are configured.
Many logging APIs lock the module-level lock. If such an API is called from this method, it could cause a deadlock if a configuration call is made on another thread, because that thread will try to acquire the module-level lock before the handler-level lock, whereas this thread tries to acquire the module-level lock after the handler-level lock (because in this method, the handler-level lock has already been acquired).

For a list of handlers included as standard, see logging.handlers .

Formatter 对象 ¶

class logging. Formatter ( fmt = None , datefmt = None , style = '%' , validate = True , * , defaults = None ) ¶

Responsible for converting a LogRecord to an output string to be interpreted by a human or external system.

参数 :

fmt ( str ) – A format string in the given style for the logged output as a whole. The possible mapping keys are drawn from the LogRecord 对象的 LogRecord 属性。若未指定， '%(message)s' is used, which is just the logged message.
datefmt ( str ) – A format string in the given style for the date/time portion of the logged output. If not specified, the default described in formatTime() 被使用。
style ( str ) – Can be one of '%' , '{' or '$' and determines how the format string will be merged with its data: using one of printf 样式字符串格式化 ( % ), str.format() ( { ) 或 string.Template ( $ ). This only applies to fmt and datefmt (如 '%(message)s' versus '{message}' ), not to the actual log messages passed to the logging methods. However, there are other ways 要使用 { - and $ -formatting for log messages.
validate ( bool ) – If True (the default), incorrect or mismatched fmt and style 将引发 ValueError ; for example, logging.Formatter('%(asctime)s - %(message)s', style='{') .
defaults ( dict [ str , 任何 ] ) – A dictionary with default values to use in custom fields. For example, logging.Formatter('%(ip)s %(message)s', defaults={"ip": None})

3.2 版改变：添加 style 参数。

3.8 版改变：添加 validate 参数。

3.10 版改变：添加 defaults 参数。

format ( record ) ¶

The record’s attribute dictionary is used as the operand to a string formatting operation. Returns the resulting string. Before formatting the dictionary, a couple of preparatory steps are carried out. The message attribute of the record is computed using msg % args . If the formatting string contains '(asctime)' , formatTime() is called to format the event time. If there is exception information, it is formatted using formatException() and appended to the message. Note that the formatted exception information is cached in attribute exc_text . This is useful because the exception information can be pickled and sent across the wire, but you should be careful if you have more than one Formatter subclass which customizes the formatting of exception information. In this case, you will have to clear the cached value (by setting the exc_text 属性为 None ) after a formatter has done its formatting, so that the next formatter to handle the event doesn’t use the cached value, but recalculates it afresh.

If stack information is available, it’s appended after the exception information, using formatStack() to transform it if necessary.

formatTime ( record , datefmt = None ) ¶

This method should be called from format() by a formatter which wants to make use of a formatted time. This method can be overridden in formatters to provide for any specific requirement, but the basic behavior is as follows: if datefmt (a string) is specified, it is used with time.strftime() to format the creation time of the record. Otherwise, the format ‘%Y-%m-%d %H:%M:%S,uuu’ is used, where the uuu part is a millisecond value and the other letters are as per the time.strftime() documentation. An example time in this format is 2003-01-23 00:29:50,411 . The resulting string is returned.

This function uses a user-configurable function to convert the creation time to a tuple. By default, time.localtime() is used; to change this for a particular formatter instance, set the converter attribute to a function with the same signature as time.localtime() or time.gmtime() . To change it for all formatters, for example if you want all logging times to be shown in GMT, set the converter attribute in the Formatter 类。

3.3 版改变： Previously, the default format was hard-coded as in this example: 2010-09-06 22:38:15,292 where the part before the comma is handled by a strptime format string ( '%Y-%m-%d %H:%M:%S' ), and the part after the comma is a millisecond value. Because strptime does not have a format placeholder for milliseconds, the millisecond value is appended using another format string, '%s,%03d' — and both of these format strings have been hardcoded into this method. With the change, these strings are defined as class-level attributes which can be overridden at the instance level when desired. The names of the attributes are default_time_format (for the strptime format string) and default_msec_format (for appending the millisecond value).

3.9 版改变： The default_msec_format 可以是 None .

formatException ( exc_info ) ¶: Formats the specified exception information (a standard exception tuple as returned by sys.exc_info() ) as a string. This default implementation just uses traceback.print_exception() . The resulting string is returned.

formatStack ( stack_info ) ¶: Formats the specified stack information (a string as returned by traceback.print_stack() , but with the last newline removed) as a string. This default implementation just returns the input value.

class logging. BufferingFormatter ( linefmt = None ) ¶

A base formatter class suitable for subclassing when you want to format a number of records. You can pass a Formatter instance which you want to use to format each line (that corresponds to a single record). If not specified, the default formatter (which just outputs the event message) is used as the line formatter.

formatHeader ( records ) ¶: Return a header for a list of records . The base implementation just returns the empty string. You will need to override this method if you want specific behaviour, e.g. to show the count of records, a title or a separator line.

formatFooter ( records ) ¶: Return a footer for a list of records . The base implementation just returns the empty string. You will need to override this method if you want specific behaviour, e.g. to show the count of records or a separator line.

format ( records ) ¶: Return formatted text for a list of records . The base implementation just returns the empty string if there are no records; otherwise, it returns the concatenation of the header, each record formatted with the line formatter, and the footer.

过滤器对象 ¶

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. 过滤 ( name = '' ) ¶

Returns an instance of the Filter 类。若 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 false for no, true for yes. Filters can either modify log records in-place or return a completely different record instance which will replace the original log record in any future processing of the event.

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.

3.2 版改变： You don’t need to create specialized Filter classes, or use other classes with a filter method: you can use a function (or other callable) as a filter. The filtering logic will check to see if the filter object has a filter attribute: if it does, it’s assumed to be a Filter 及其 filter() method is called. Otherwise, it’s assumed to be a callable and called with the record as the single parameter. The returned value should conform to that returned by filter() .

Changed in version 3.12: You can now return a LogRecord instance from filters to replace the log record rather than modifying it in place. This allows filters attached to a Handler to modify the log record before it is emitted, without having side effects on other handlers.

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 ).

LogRecord 对象 ¶

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 , sinfo = 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 attribute of the record.

参数 :

名称 ( str ) – The name of the logger used to log the event represented by this LogRecord . Note that the logger name in the LogRecord will always have this value, even though it may be emitted by a handler attached to a different (ancestor) logger.
level ( int ) – The numeric level of the logging event (such as 10 for DEBUG , 20 for 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 ( str ) – The full string path of the source file where the logging call was made.
lineno ( int ) – The line number in the source file where the logging call was made.
msg ( 任何 ) – The event description message, which can be a %-format string with placeholders for variable data, or an arbitrary object (see Using arbitrary objects as messages ).
args ( tuple | dict [ str , 任何 ] ) – Variable data to merge into the msg argument to obtain the event description.
exc_info ( tuple [ type [ BaseException ] , BaseException , types.TracebackType ] | None ) – An exception tuple with the current exception information, as returned by sys.exc_info() ，或 None if no exception information is available.
func ( str | None ) – The name of the function or method from which the logging call was invoked.
sinfo ( str | None ) – A text string representing stack information from the base of the stack in the current thread, up to the logging call.

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.

3.2 版改变： The creation of a LogRecord has been made more configurable by providing a factory which is used to create the record. The factory can be set using getLogRecordFactory() and setLogRecordFactory() (see this for the factory’s signature).

This functionality can be used to inject your own values into a LogRecord at creation time. You can use the following pattern:

old_factory = logging.getLogRecordFactory()
def record_factory(*args, **kwargs):
    record = old_factory(*args, **kwargs)
    record.custom_attribute = 0xdecafbad
    return record
logging.setLogRecordFactory(record_factory)

With this pattern, multiple factories could be chained, and as long as they don’t overwrite each other’s attributes or unintentionally overwrite the standard attributes listed above, there should be no surprises.

LogRecord 属性 ¶

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.

If you are using {}-formatting ( str.format() ), you can use {attrname} as the placeholder in the format string. If you are using $-formatting ( string.Template ), use the form ${attrname} . In both cases, of course, replace attrname with the actual attribute name you want to use.

In the case of {}-formatting, you can specify formatting flags by placing them after the attribute name, separated from it with a colon. For example: a placeholder of {msecs:03.0f} would format a millisecond value of 4 as 004 。参考 str.format() documentation for full details on the options available to you.

性名称	格式	描述
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`	用于消息的文本日志级别 ( `'DEBUG'` , `'INFO'` , `'WARNING'` , `'ERROR'` , `'CRITICAL'` ).
levelno	`%(levelno)s`	用于消息的数字日志级别 ( `DEBUG` , `INFO` , `WARNING` , `ERROR` , `CRITICAL` ).
lineno	`%(lineno)d`	Source line number where the logging call was issued (if available).
message	`%(message)s`	The logged message, computed as `msg % args` . This is set when `Formatter.format()` is invoked.
模块	`%(module)s`	Module (name portion of `filename` ).
msecs	`%(msecs)d`	Millisecond portion of the time when the `LogRecord` was created.
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 ).
名称	`%(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.
stack_info	You shouldn’t need to format this yourself.	Stack frame information (where available) from the bottom of the stack in the current thread, up to and including the stack frame of the logging call which resulted in the creation of this record.
thread	`%(thread)d`	Thread ID (if available).
threadName	`%(threadName)s`	Thread name (if available).
taskName	`%(taskName)s`	`asyncio.Task` name (if available).

3.1 版改变： processName 被添加。

Changed in version 3.12: taskName 被添加。

LoggerAdapter 对象 ¶

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 ) ¶

返回实例化的 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.

manager ¶: Delegates to the underlying manager` on logger .

_log ¶: Delegates to the underlying _log`() method on logger .

In addition to the above, LoggerAdapter supports the following methods of Logger : debug() , info() , warning() , error() , exception() , critical() , log() , isEnabledFor() , getEffectiveLevel() , setLevel() and hasHandlers() . These methods have the same signatures as their counterparts in Logger , so you can use the two types of instances interchangeably.

3.2 版改变： The isEnabledFor() , getEffectiveLevel() , setLevel() and hasHandlers() methods were added to LoggerAdapter . These methods delegate to the underlying logger.

3.6 版改变：属性 manager 和方法 _log() were added, which delegate to the underlying logger and allow adapters to be nested.

线程安全 ¶

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.

模块级函数 ¶

除上文描述的类外，还有许多模块级函数。

logging. getLogger ( name = None ) ¶

logging. getLoggerClass ( ) ¶

logging. getLogRecordFactory ( ) ¶

logging. debug ( msg , * args , ** kwargs ) ¶

logging. info ( msg , * args , ** kwargs ) ¶

logging. warning ( msg , * args , ** kwargs ) ¶

logging. error ( msg , * args , ** kwargs ) ¶

logging. critical ( msg , * args , ** kwargs ) ¶

logging. exception ( msg , * args , ** kwargs ) ¶

logging. log ( level , msg , * args , ** kwargs ) ¶

logging. disable ( level = CRITICAL ) ¶

logging. addLevelName ( level , levelName ) ¶

logging. getLevelNamesMapping ( ) ¶

logging. getLevelName ( level ) ¶

logging. getHandlerByName ( name ) ¶

logging. getHandlerNames ( ) ¶

logging. makeLogRecord ( attrdict ) ¶

logging. basicConfig ( ** kwargs ) ¶

logging. shutdown ( ) ¶

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. After this call, as at any other time, do not instantiate loggers directly using the subclass: continue to use the logging.getLogger() API to get your loggers.

logging. setLogRecordFactory ( factory ) ¶

Set a callable which is used to create a LogRecord .

参数 :: factory – The factory callable to be used to instantiate a log record.

Added in version 3.2: 此函数有提供，除了 getLogRecordFactory() ，要允许开发者更多地控制如何 LogRecord representing a logging event is constructed.

工厂有以下签名：

factory(name, level, fn, lno, msg, args, exc_info, func=None, sinfo=None, **kwargs)

名称 :

The logger name.

level :

The logging level (numeric).

fn :

The full pathname of the file where the logging call was made.

lno :

The line number in the file where the logging call was made.

msg :

日志消息。

args :

The arguments for the logging message.

exc_info :

异常元组，或 None .

func :

The name of the function or method which invoked the logging call.

sinfo :

A stack traceback such as is provided by traceback.print_stack() , showing the call hierarchy.

kwargs :

Additional keyword arguments.

模块级属性 ¶

logging. lastResort ¶

A “handler of last resort” is available through this attribute. This is a StreamHandler writing to sys.stderr with a level of WARNING , and is used to handle logging events in the absence of any logging configuration. The end result is to just print the message to sys.stderr . This replaces the earlier error message saying that “no handlers could be found for logger XYZ”. If you need the earlier behaviour for some reason, lastResort can be set to None .

Added in version 3.2.

logging. raiseExceptions ¶

Used to see if exceptions during handling should be propagated.

默认： True .

若 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.

集成警告模块 ¶

The captureWarnings() 函数可以用于集成 logging 采用 warnings 模块。

logging. captureWarnings ( capture ) ¶

This function is used to turn the capture of warnings by logging on and off.

若 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 .

若 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).

另请参阅

模块 logging.config: 用于 logging 模块的配置 API。
模块 logging.handlers: 包括于 logging 模块中的有用处理程序。
PEP 282 - 日志系统: 描述将此特征包括在 Python 标准库的提案。
原始 Python 日志包: 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.