logging
— Python 日志设施
¶
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。
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).
下面列出了由模块定义的基本类及其函数。
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
. 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.
logging.
Logger
¶
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.
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.
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.
3.2 版新增。
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)-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
Formatter
s would be used with particular
Handler
。
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。
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。
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.
3.2 版新增。
3.7 版改变： 日志器现在可以被腌制和取消腌制。
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 |
|---|---|
CRITICAL
|
50 |
ERROR
|
40 |
WARNING
|
30 |
INFO
|
20 |
DEBUG
|
10 |
NOTSET
|
0 |
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__()
.
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()
.
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
.
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
.
For a list of handlers included as standard, see
logging.handlers
.
Formatter
对象拥有下列属性和方法。它们负责转换
LogRecord
到 (通常) 字符串，可以被人类或外部系统所解释。基
Formatter
allows a formatting string to be specified. If none is supplied, the default value of
'%(message)s'
is used, which just includes the message in the logging call. To have additional items of information in the formatted output (such as a timestamp), keep reading.
A Formatter can be initialized with a format string which makes use of knowledge of the
LogRecord
attributes - such as the default value mentioned above making use of the fact that the user’s message and arguments are pre-formatted into a
LogRecord
’s
message
attribute. This format string contains standard Python %-style mapping keys. See section
printf 样式字符串格式化
for more information on string formatting.
The useful mapping keys in a
LogRecord
are given in the section on
LogRecord 属性
.
logging.
Formatter
(
fmt=None
,
datefmt=None
,
style='%'
)
¶
返回新的实例化
Formatter
class. The instance is initialized with a format string for the message as a whole, as well as a format string for the date/time portion of a message. If no
fmt
被指定，
'%(message)s'
源于使用。若无
datefmt
is specified, a format is used which is described in the
formatTime()
文档编制。
The
style
parameter can be one of ‘%’, ‘{’ or ‘$’ and determines how the format string will be merged with its data: using one of %-formatting,
str.format()
or
string.Template
。见
在整个应用程序中使用特定格式化样式
for more information on using {- and $-formatting for log messages.
3.2 版改变： The style 参数被添加。
3.8 版改变：
The
validate
parameter was added. Incorrect or mismatched style and fmt will raise a
ValueError
。例如：
logging.Formatter('%(asctime)s - %(message)s', style='{')
.
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 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).
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.
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.
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 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.
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()
.
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
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).
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
field of the record.
名称 – 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.
sinfo – 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.
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:03d}
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). |
3.1 版改变： processName 被添加。
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
.
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.
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.
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.
除上文描述的类外，还有许多模块级函数。
logging.
getLogger
(
name=None
)
¶
返回具有指定名称的日志器，或者若名称为
None
，返回是层次结构根日志器的日志器。若指定，名称通常是点分隔的分层名称，像
‘a’
,
‘a.b’
or
‘a.b.c.d’
。这些名称的选取完全取决于使用日志记录的开发者。
采用给定名称调用此函数全部返回同一日志器实例。这意味着日志器实例从不需要在应用程序的不同部分之间传递。
logging.
getLoggerClass
(
)
¶
返回标准
Logger
类，或最后类被传递给
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.
getLogRecordFactory
(
)
¶
返回的可调用被用于创建
LogRecord
.
3.2 版新增：
此函数有提供，除了
setLogRecordFactory()
，要允许开发者更多地控制如何
LogRecord
representing a logging event is constructed.
见
setLogRecordFactory()
for more information about the how the factory is called.
logging.
debug
(
msg
,
*args
,
**kwargs
)
¶
日志消息采用级别
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 three 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()
) 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 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
Formatter
s would be used with particular
Handler
。
3.2 版改变： The stack_info 参数被添加。
logging.
info
(
msg
,
*args
,
**kwargs
)
¶
日志消息采用级别
INFO
on the root logger. The arguments are interpreted as for
debug()
.
logging.
warning
(
msg
,
*args
,
**kwargs
)
¶
日志消息采用级别
WARNING
on the root logger. The arguments are interpreted as for
debug()
.
注意
There is an obsolete function
warn
功能等同于
warning
. As
warn
被弃用，请不要使用它 - 使用
warning
代替。
logging.
error
(
msg
,
*args
,
**kwargs
)
¶
日志消息采用级别
ERROR
on the root logger. The arguments are interpreted as for
debug()
.
logging.
critical
(
msg
,
*args
,
**kwargs
)
¶
日志消息采用级别
CRITICAL
on the root logger. The arguments are interpreted as for
debug()
.
logging.
exception
(
msg
,
*args
,
**kwargs
)
¶
日志消息采用级别
ERROR
on the root logger. The arguments are interpreted as for
debug()
. Exception info is added to the logging message. This function should only be called from an exception handler.
logging.
log
(
level
,
msg
,
*args
,
**kwargs
)
¶
日志消息采用级别
level
on the root logger. The other arguments are interpreted as for
debug()
.
注意
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
(
level=CRITICAL
)
¶
Provides an overriding level
level
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
level
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.
Note that if you have defined any custom logging level higher than
CRITICAL
(this is not recommended), you won’t be able to rely on the default value for the
level
parameter, but will have to explicitly supply a suitable value.
3.7 版改变：
The
level
parameter was defaulted to level
CRITICAL
。见
bpo-28524
for more information about this change.
logging.
addLevelName
(
level
,
levelName
)
¶
Associates level
level
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.
注意
If you are thinking of defining your own levels, please see the section on 自定义级别 .
logging.
getLevelName
(
level
)
¶
Returns the textual or numeric representation of logging level level .
若
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
level
is returned. If a numeric value corresponding to one of the defined levels is passed in, the corresponding string representation is returned.
The level parameter also accepts a string representation of the level such as ‘INFO’. In such cases, this functions returns the corresponding numeric value of the level.
If no matching numeric or string value is passed in, the string ‘Level %s’ % level is returned.
注意
Levels are internally integers (as they need to be compared in the logging logic). 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 属性
), and vice versa.
3.4 版改变： In Python versions earlier than 3.4, this function could also be passed a text level, and would return the corresponding numeric value of the level. This undocumented behaviour was considered a mistake, and was removed in Python 3.4, but reinstated in 3.4.2 due to retain backward compatibility.
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()
将调用
basicConfig()
automatically if no handlers are defined for the root logger.
This function does nothing if the root logger already has handlers configured, unless the keyword argument
force
被设为
True
.
注意
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.
| 格式 | 描述 |
|---|---|
| filename | Specifies that a FileHandler be created, using the specified filename, rather than a StreamHandler. |
| filemode |
若
filename
is specified, open the file in this
mode
。默认为
'a'
.
|
| format |
Use the specified format string for the handler. Defaults to attributes
levelname
,
name
and
message
separated by colons.
|
| datefmt |
Use the specified date/time format, as accepted by
time.strftime()
.
|
| style |
若
format
is specified, use this style for the format string. One of
'%'
,
'{'
or
'$'
for
printf-style
,
str.format()
or
string.Template
respectively. Defaults to
'%'
.
|
| 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, a
ValueError
被引发。
|
| handlers |
If specified, this should be an iterable of already created handlers to add to the root logger. Any handlers which don’t already have a formatter set will be assigned the default formatter created in this function. Note that this argument is incompatible with
filename
or
stream
- if both are present, a
ValueError
被引发。
|
| force | If this keyword argument is specified as true, any existing handlers attached to the root logger are removed and closed, before carrying out the configuration as specified by the other arguments. |
3.2 版改变： The style 自变量被添加。
3.3 版改变： The handlers argument was added. Additional checks were added to catch situations where incompatible arguments are specified (e.g. handlers together with stream or filename ，或 stream together with filename ).
3.8 版改变： The force 自变量被添加。
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.
When the logging module is imported, it registers this function as an exit handler (see
atexit
), so normally there’s no need to do that manually.
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.
factory – The factory callable to be used to instantiate a log record.
3.2 版新增：
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)
The logger name.
The logging level (numeric).
The full pathname of the file where the logging call was made.
The line number in the file where the logging call was made.
日志消息。
The arguments for the logging message.
异常元组，或
None
.
The name of the function or method which invoked the logging call.
A stack traceback such as is provided by
traceback.print_stack()
, showing the call hierarchy.
Additional keyword arguments.
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
.
3.2 版新增。
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
logging.config
用于 logging 模块的配置 API。
logging.handlers
包括于 logging 模块中的有用处理程序。
描述将此特征包括在 Python 标准库的提案。
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.