`logging.handlers` — 日志处理程序 ¶

包中提供了下列有用处理程序。注意，其中 3 个处理程序 ( StreamHandler , FileHandler and NullHandler ) 实际定义在 logging 模块本身，但已文档化在此除其它处理程序外。

StreamHandler ¶

The StreamHandler 类，位于核心 logging 包，将日志记录输出发送给流，譬如 sys.stdout , sys.stderr 或任何像文件对象 (或更准确地说，任何对象支持 write() and flush() 方法)。

class logging. StreamHandler ( stream = None ) ¶

返回新的实例化 StreamHandler 类。若 stream 有指定，实例将使用它为日志记录输出；否则， sys.stderr 会被使用。

emit ( record ) ¶: If a formatter is specified, it is used to format the record. The record is then written to the stream followed by terminator . If exception information is present, it is formatted using traceback.print_exception() and appended to the stream.

flush ( ) ¶: 刷新流通过调用其 flush() 方法。注意， close() method is inherited from Handler and so does no output, so an explicit flush() call may be needed at times.

setStream ( stream ) ¶

Sets the instance’s stream to the specified value, if it is different. The old stream is flushed before the new stream is set.

参数 :: stream – The stream that the handler should use.
返回 :: the old stream, if the stream was changed, or None if it wasn’t.

3.7 版添加。

terminator ¶

String used as the terminator when writing a formatted record to a stream. Default value is '\n' .

If you don’t want a newline termination, you can set the handler instance’s terminator attribute to the empty string.

In earlier versions, the terminator was hardcoded as '\n' .

Added in version 3.2.

FileHandler ¶

The FileHandler 类，位于核心 logging package, sends logging output to a disk file. It inherits the output functionality from StreamHandler .

class logging. FileHandler ( filename , mode = 'a' , encoding = None , delay = False , errors = None ) ¶

返回新的实例化 FileHandler 类。打开指定文件并用作日志记录流。若 mode 未指定， 'a' 被使用。若 encoding 不是 None ，用于采用该编码打开文件。若 delay 为 True，则延迟打开文件直到首次调用 emit() 。默认情况下，文件会无限增长。若 errors is specified, it’s used to determine how encoding errors are handled.

3.6 版改变：除字符串值外， Path 对象也接受为 filename 自变量。

3.9 版改变： The errors 参数被添加。

close ( ) ¶: 关闭文件。

emit ( record ) ¶

将记录输出到文件。

Note that if the file was closed due to logging shutdown at exit and the file mode is ‘w’, the record will not be emitted (see bpo-42378 ).

NullHandler ¶

Added in version 3.1.

The NullHandler 类，位于核心 logging package, does not do any formatting or output. It is essentially a ‘no-op’ handler for use by library developers.

class logging. NullHandler ¶

返回新的实例化 NullHandler 类。

emit ( record ) ¶: This method does nothing.

handle ( record ) ¶: This method does nothing.

createLock ( ) ¶: 此方法返回 None for the lock, since there is no underlying I/O to which access needs to be serialized.

见 Configuring Logging for a Library for more information on how to use NullHandler .

WatchedFileHandler ¶

The WatchedFileHandler 类，位于 logging.handlers module, is a FileHandler which watches the file it is logging to. If the file changes, it is closed and reopened using the file name.

A file change can happen because of usage of programs such as newsyslog and logrotate which perform log file rotation. This handler, intended for use under Unix/Linux, watches the file to see if it has changed since the last emit. (A file is deemed to have changed if its device or inode have changed.) If the file has changed, the old file stream is closed, and the file opened to get a new stream.

This handler is not appropriate for use under Windows, because under Windows open log files cannot be moved or renamed - logging opens the files with exclusive locks - and so there is no need for such a handler. Furthermore, ST_INO is not supported under Windows; stat() always returns zero for this value.

class logging.handlers. WatchedFileHandler ( filename , mode = 'a' , encoding = None , delay = False , errors = None ) ¶

返回新的实例化 WatchedFileHandler 类。打开指定文件并用作日志记录流。若 mode 未指定， 'a' 被使用。若 encoding 不是 None ，用于采用该编码打开文件。若 delay 为 True，则延迟打开文件直到首次调用 emit() 。默认情况下，文件会无限增长。若 errors 有提供，它确定如何处理编码错误。

3.6 版改变：除字符串值外， Path 对象也接受为 filename 自变量。

3.9 版改变： The errors 参数被添加。

reopenIfNeeded ( ) ¶

Checks to see if the file has changed. If it has, the existing stream is flushed and closed and the file opened again, typically as a precursor to outputting the record to the file.

Added in version 3.6.

emit ( record ) ¶: Outputs the record to the file, but first calls reopenIfNeeded() to reopen the file if it has changed.

BaseRotatingHandler ¶

The BaseRotatingHandler 类，位于 logging.handlers module, is the base class for the rotating file handlers, RotatingFileHandler and TimedRotatingFileHandler . You should not need to instantiate this class, but it has attributes and methods you may need to override.

class logging.handlers. BaseRotatingHandler ( filename , mode , encoding = None , delay = False , errors = None ) ¶

The parameters are as for FileHandler . The attributes are:

namer ¶: If this attribute is set to a callable, the rotation_filename() method delegates to this callable. The parameters passed to the callable are those passed to rotation_filename() .

注意

The namer function is called quite a few times during rollover, so it should be as simple and as fast as possible. It should also return the same output every time for a given input, otherwise the rollover behaviour may not work as expected.

It’s also worth noting that care should be taken when using a namer to preserve certain attributes in the filename which are used during rotation. For example, RotatingFileHandler expects to have a set of log files whose names contain successive integers, so that rotation works as expected, and TimedRotatingFileHandler deletes old log files (based on the backupCount parameter passed to the handler’s initializer) by determining the oldest files to delete. For this to happen, the filenames should be sortable using the date/time portion of the filename, and a namer needs to respect this. (If a namer is wanted that doesn’t respect this scheme, it will need to be used in a subclass of TimedRotatingFileHandler which overrides the getFilesToDelete() method to fit in with the custom naming scheme.)

Added in version 3.3.

rotator ¶

If this attribute is set to a callable, the rotate() method delegates to this callable. The parameters passed to the callable are those passed to rotate() .

Added in version 3.3.

rotation_filename ( default_name ) ¶

Modify the filename of a log file when rotating.

This is provided so that a custom filename can be provided.

The default implementation calls the ‘namer’ attribute of the handler, if it’s callable, passing the default name to it. If the attribute isn’t callable (the default is None ), the name is returned unchanged.

参数 :: default_name – The default name for the log file.

Added in version 3.3.

rotate ( source , dest ) ¶

When rotating, rotate the current log.

The default implementation calls the ‘rotator’ attribute of the handler, if it’s callable, passing the source and dest arguments to it. If the attribute isn’t callable (the default is None ), the source is simply renamed to the destination.

参数 :

source – The source filename. This is normally the base filename, e.g. ‘test.log’.
dest – The destination filename. This is normally what the source is rotated to, e.g. ‘test.log.1’.

Added in version 3.3.

The reason the attributes exist is to save you having to subclass - you can use the same callables for instances of RotatingFileHandler and TimedRotatingFileHandler . If either the namer or rotator callable raises an exception, this will be handled in the same way as any other exception during an emit() call, i.e. via the handleError() method of the handler.

If you need to make more significant changes to rotation processing, you can override the methods.

For an example, see Using a rotator and namer to customize log rotation processing .

RotatingFileHandler ¶

The RotatingFileHandler 类，位于 logging.handlers 模块，支持轮换磁盘日志文件。

class logging.handlers. RotatingFileHandler ( filename , mode = 'a' , maxBytes = 0 , backupCount = 0 , encoding = None , delay = False , errors = None ) ¶

返回新的实例化 RotatingFileHandler 类。打开指定文件并用作日志记录流。若 mode 未指定， 'a' 被使用。若 encoding 不是 None ，用于采用该编码打开文件。若 delay 为 True，则延迟打开文件直到首次调用 emit() 。默认情况下，文件会无限增长。若 errors 有提供，它确定如何处理编码错误。

可以使用 maxBytes and backupCount 值以允许文件 rollover 按预先确定大小。当大小即将超过时，关闭文件并为输出默默打开新文件。出现翻转每当当前日志文件接近 maxBytes 长度；但是若 maxBytes or backupCount 为 0，从不出现翻转，所以，一般来说需要设置 backupCount 到至少 1，且拥有非零 maxBytes 。当 backupCount 非 0，系统将通过追加扩展名 .1、.2 等到文件名以保存旧日志文件。例如，采用 backupCount 5 和基文件名 app.log ，将获得 app.log , app.log.1 , app.log.2 ，直到 app.log.5 。正写入的文件始终是 app.log 。当填充此文被时，关闭它并重命名为 app.log.1 ，及若文件 app.log.1 , app.log.2 等存在，那么将它们重命名为 app.log.2 , app.log.3 等分别。

3.6 版改变：除字符串值外， Path 对象也接受为 filename 自变量。

3.9 版改变： The errors 参数被添加。

doRollover ( ) ¶: 进行翻转，如上所述。

emit ( record ) ¶: 将记录输出到文件，以迎合先前描述的翻转。

TimedRotatingFileHandler ¶

The TimedRotatingFileHandler 类，位于 logging.handlers 模块，支持按一定时间间隔轮换磁盘日志文件。

class logging.handlers. TimedRotatingFileHandler ( filename , 当 = 'h' , interval = 1 , backupCount = 0 , encoding = None , delay = False , utc = False , atTime = None , errors = None ) ¶

返回新的实例化 TimedRotatingFileHandler class. The specified file is opened and used as the stream for logging. On rotating it also sets the filename suffix. Rotating happens based on the product of 当 and interval .

可以使用当 to specify the type of interval . The list of possible values is below. Note that they are not case sensitive.

值	Type of interval	If/how atTime is used
`'S'`	Seconds	忽略
`'M'`	Minutes	忽略
`'H'`	Hours	忽略
`'D'`	Days	忽略
`'W0'-'W6'`	Weekday (0=Monday)	Used to compute initial rollover time
`'midnight'`	Roll over at midnight, if atTime not specified, else at time atTime	Used to compute initial rollover time

When using weekday-based rotation, specify ‘W0’ for Monday, ‘W1’ for Tuesday, and so on up to ‘W6’ for Sunday. In this case, the value passed for interval isn’t used.

The system will save old log files by appending extensions to the filename. The extensions are date-and-time based, using the strftime format %Y-%m-%d_%H-%M-%S or a leading portion thereof, depending on the rollover interval.

When computing the next rollover time for the first time (when the handler is created), the last modification time of an existing log file, or else the current time, is used to compute when the next rotation will occur.

若 utc argument is true, times in UTC will be used; otherwise local time is used.

若 backupCount is nonzero, at most backupCount files will be kept, and if more would be created when rollover occurs, the oldest one is deleted. The deletion logic uses the interval to determine which files to delete, so changing the interval may leave old files lying around.

若 delay 为 True，则延迟打开文件直到首次调用 emit() .

若 atTime 不是 None ，它必须是 datetime.time instance which specifies the time of day when rollover occurs, for the cases where rollover is set to happen “at midnight” or “on a particular weekday”. Note that in these cases, the atTime value is effectively used to compute the initial rollover, and subsequent rollovers would be calculated via the normal interval calculation.

若 errors is specified, it’s used to determine how encoding errors are handled.

注意

Calculation of the initial rollover time is done when the handler is initialised. Calculation of subsequent rollover times is done only when rollover occurs, and rollover occurs only when emitting output. If this is not kept in mind, it might lead to some confusion. For example, if an interval of “every minute” is set, that does not mean you will always see log files with times (in the filename) separated by a minute; if, during application execution, logging output is generated more frequently than once a minute, then you can expect to see log files with times separated by a minute. If, on the other hand, logging messages are only output once every five minutes (say), then there will be gaps in the file times corresponding to the minutes where no output (and hence no rollover) occurred.

3.4 版改变： atTime 参数被添加。

3.6 版改变：除字符串值外， Path 对象也接受为 filename 自变量。

3.9 版改变： The errors 参数被添加。

doRollover ( ) ¶: 进行翻转，如上所述。

emit ( record ) ¶: Outputs the record to the file, catering for rollover as described above.

getFilesToDelete ( ) ¶: Returns a list of filenames which should be deleted as part of rollover. These are the absolute paths of the oldest backup log files written by the handler.

SocketHandler ¶

The SocketHandler 类，位于 logging.handlers module, sends logging output to a network socket. The base class uses a TCP socket.

class logging.handlers. SocketHandler ( host , port ) ¶

返回新的实例化 SocketHandler class intended to communicate with a remote machine whose address is given by host and port .

3.4 版改变：若 port is specified as None , a Unix domain socket is created using the value in host - otherwise, a TCP socket is created.

close ( ) ¶: 关闭套接字。

emit ( ) ¶: Pickles the record’s attribute dictionary and writes it to the socket in binary format. If there is an error with the socket, silently drops the packet. If the connection was previously lost, re-establishes the connection. To unpickle the record at the receiving end into a LogRecord ，使用 makeLogRecord() 函数。

handleError ( ) ¶: Handles an error which has occurred during emit() . The most likely cause is a lost connection. Closes the socket so that we can retry on the next event.

makeSocket ( ) ¶: This is a factory method which allows subclasses to define the precise type of socket they want. The default implementation creates a TCP socket ( socket.SOCK_STREAM ).

makePickle ( record ) ¶

Pickles the record’s attribute dictionary in binary format with a length prefix, and returns it ready for transmission across the socket. The details of this operation are equivalent to:

data = pickle.dumps(record_attr_dict, 1)
datalen = struct.pack('>L', len(data))
return datalen + data

Note that pickles aren’t completely secure. If you are concerned about security, you may want to override this method to implement a more secure mechanism. For example, you can sign pickles using HMAC and then verify them on the receiving end, or alternatively you can disable unpickling of global objects on the receiving end.

send ( packet ) ¶

Send a pickled byte-string packet to the socket. The format of the sent byte-string is as described in the documentation for makePickle() .

This function allows for partial sends, which can happen when the network is busy.

createSocket ( ) ¶

Tries to create a socket; on failure, uses an exponential back-off algorithm. On initial failure, the handler will drop the message it was trying to send. When subsequent messages are handled by the same instance, it will not try connecting until some time has passed. The default parameters are such that the initial delay is one second, and if after that delay the connection still can’t be made, the handler will double the delay each time up to a maximum of 30 seconds.

This behaviour is controlled by the following handler attributes:

retryStart (initial delay, defaulting to 1.0 seconds).
retryFactor (multiplier, defaulting to 2.0).
retryMax (maximum delay, defaulting to 30.0 seconds).

This means that if the remote listener starts up after the handler has been used, you could lose messages (since the handler won’t even attempt a connection until the delay has elapsed, but just silently drop messages during the delay period).

DatagramHandler ¶

The DatagramHandler 类，位于 logging.handlers 模块，继承自 SocketHandler 以支持通过 UDP 套接字发送日志消息。

class logging.handlers. DatagramHandler ( host , port ) ¶

返回新的实例化 DatagramHandler class intended to communicate with a remote machine whose address is given by host and port .

注意

As UDP is not a streaming protocol, there is no persistent connection between an instance of this handler and host . For this reason, when using a network socket, a DNS lookup might have to be made each time an event is logged, which can introduce some latency into the system. If this affects you, you can do a lookup yourself and initialize this handler using the looked-up IP address rather than the hostname.

3.4 版改变：若 port is specified as None , a Unix domain socket is created using the value in host - otherwise, a UDP socket is created.

emit ( ) ¶: Pickles the record’s attribute dictionary and writes it to the socket in binary format. If there is an error with the socket, silently drops the packet. To unpickle the record at the receiving end into a LogRecord ，使用 makeLogRecord() 函数。

makeSocket ( ) ¶: The factory method of SocketHandler is here overridden to create a UDP socket ( socket.SOCK_DGRAM ).

send ( s ) ¶: Send a pickled byte-string to a socket. The format of the sent byte-string is as described in the documentation for SocketHandler.makePickle() .

SysLogHandler ¶

The SysLogHandler 类，位于 logging.handlers module, supports sending logging messages to a remote or local Unix syslog.

class logging.handlers. SysLogHandler ( address = ('localhost', SYSLOG_UDP_PORT) , facility = LOG_USER , socktype = socket.SOCK_DGRAM ) ¶

返回新的实例化 SysLogHandler class intended to communicate with a remote Unix machine whose address is given by address in the form of a (host, port) tuple. If address 未指定， ('localhost', 514) is used. The address is used to open a socket. An alternative to providing a (host, port) tuple is providing an address as a string, for example ‘/dev/log’. In this case, a Unix domain socket is used to send the message to the syslog. If facility 未指定， LOG_USER is used. The type of socket opened depends on the socktype argument, which defaults to socket.SOCK_DGRAM and thus opens a UDP socket. To open a TCP socket (for use with the newer syslog daemons such as rsyslog), specify a value of socket.SOCK_STREAM .

Note that if your server is not listening on UDP port 514, SysLogHandler may appear not to work. In that case, check what address you should be using for a domain socket - it’s system dependent. For example, on Linux it’s usually ‘/dev/log’ but on OS/X it’s ‘/var/run/syslog’. You’ll need to check your platform and use the appropriate address (you may need to do this check at runtime if your application needs to run on several platforms). On Windows, you pretty much have to use the UDP option.

注意

On macOS 12.x (Monterey), Apple has changed the behaviour of their syslog daemon - it no longer listens on a domain socket. Therefore, you cannot expect SysLogHandler to work on this system.

见 gh-91070 了解更多信息。

3.2 版改变： socktype 被添加。

close ( ) ¶: 关闭到远程主机的套接字。

createSocket ( ) ¶

Tries to create a socket and, if it’s not a datagram socket, connect it to the other end. This method is called during handler initialization, but it’s not regarded as an error if the other end isn’t listening at this point - the method will be called again when emitting an event, if there is no socket at that point.

Added in version 3.11.

emit ( record ) ¶

The record is formatted, and then sent to the syslog server. If exception information is present, it is not sent to the server.

3.2.1 版改变： (见： bpo-12168 .) In earlier versions, the message sent to the syslog daemons was always terminated with a NUL byte, because early versions of these daemons expected a NUL terminated message - even though it’s not in the relevant specification ( RFC 5424 ). More recent versions of these daemons don’t expect the NUL byte but strip it off if it’s there, and even more recent daemons (which adhere more closely to RFC 5424) pass the NUL byte on as part of the message.

To enable easier handling of syslog messages in the face of all these differing daemon behaviours, the appending of the NUL byte has been made configurable, through the use of a class-level attribute, append_nul . This defaults to True (preserving the existing behaviour) but can be set to False 在 SysLogHandler instance in order for that instance to not append the NUL terminator.

3.3 版改变： (见： bpo-12419 .) In earlier versions, there was no facility for an “ident” or “tag” prefix to identify the source of the message. This can now be specified using a class-level attribute, defaulting to "" to preserve existing behaviour, but which can be overridden on a SysLogHandler instance in order for that instance to prepend the ident to every message handled. Note that the provided ident must be text, not bytes, and is prepended to the message exactly as is.

encodePriority ( facility , priority ) ¶

Encodes the facility and priority into an integer. You can pass in strings or integers - if strings are passed, internal mapping dictionaries are used to convert them to integers.

The symbolic LOG_ values are defined in SysLogHandler and mirror the values defined in the sys/syslog.h 头文件。

Priorities

Name (string)	Symbolic value
`alert`	LOG_ALERT
`crit` or `critical`	LOG_CRIT
`debug`	LOG_DEBUG
`emerg` or `panic`	LOG_EMERG
`err` or `error`	LOG_ERR
`info`	LOG_INFO
`notice`	LOG_NOTICE
`warn` or `warning`	LOG_WARNING

Facilities

Name (string)	Symbolic value
`auth`	LOG_AUTH
`authpriv`	LOG_AUTHPRIV
`cron`	LOG_CRON
`daemon`	LOG_DAEMON
`ftp`	LOG_FTP
`kern`	LOG_KERN
`lpr`	LOG_LPR
`mail`	LOG_MAIL
`news`	LOG_NEWS
`syslog`	LOG_SYSLOG
`user`	LOG_USER
`uucp`	LOG_UUCP
`local0`	LOG_LOCAL0
`local1`	LOG_LOCAL1
`local2`	LOG_LOCAL2
`local3`	LOG_LOCAL3
`local4`	LOG_LOCAL4
`local5`	LOG_LOCAL5
`local6`	LOG_LOCAL6
`local7`	LOG_LOCAL7

mapPriority ( levelname ) ¶: Maps a logging level name to a syslog priority name. You may need to override this if you are using custom levels, or if the default algorithm is not suitable for your needs. The default algorithm maps DEBUG , INFO , WARNING , ERROR and CRITICAL to the equivalent syslog names, and all other level names to ‘warning’.

NTEventLogHandler ¶

The NTEventLogHandler 类，位于 logging.handlers module, supports sending logging messages to a local Windows NT, Windows 2000 or Windows XP event log. Before you can use it, you need Mark Hammond’s Win32 extensions for Python installed.

class logging.handlers. NTEventLogHandler ( appname , dllname = None , logtype = 'Application' ) ¶

返回新的实例化 NTEventLogHandler 类。 appname is used to define the application name as it appears in the event log. An appropriate registry entry is created using this name. The dllname should give the fully qualified pathname of a .dll or .exe which contains message definitions to hold in the log (if not specified, 'win32service.pyd' is used - this is installed with the Win32 extensions and contains some basic placeholder message definitions. Note that use of these placeholders will make your event logs big, as the entire message source is held in the log. If you want slimmer logs, you have to pass in the name of your own .dll or .exe which contains the message definitions you want to use in the event log). The logtype 是某一 'Application' , 'System' or 'Security' , and defaults to 'Application' .

close ( ) ¶: At this point, you can remove the application name from the registry as a source of event log entries. However, if you do this, you will not be able to see the events as you intended in the Event Log Viewer - it needs to be able to access the registry to get the .dll name. The current version does not do this.

emit ( record ) ¶: Determines the message ID, event category and event type, and then logs the message in the NT event log.

getEventCategory ( record ) ¶: Returns the event category for the record. Override this if you want to specify your own categories. This version returns 0.

getEventType ( record ) ¶: Returns the event type for the record. Override this if you want to specify your own types. This version does a mapping using the handler’s typemap attribute, which is set up in __init__() to a dictionary which contains mappings for DEBUG , INFO , WARNING , ERROR and CRITICAL . If you are using your own levels, you will either need to override this method or place a suitable dictionary in the handler’s typemap 属性。

getMessageID ( record ) ¶: Returns the message ID for the record. If you are using your own messages, you could do this by having the msg passed to the logger being an ID rather than a format string. Then, in here, you could use a dictionary lookup to get the message ID. This version returns 1, which is the base message ID in win32service.pyd .

SMTPHandler ¶

The SMTPHandler 类，位于 logging.handlers module, supports sending logging messages to an email address via SMTP.

class logging.handlers. SMTPHandler ( mailhost , fromaddr , toaddrs , subject , credentials = None , secure = None , timeout = 1.0 ) ¶

返回新的实例化 SMTPHandler class. The instance is initialized with the from and to addresses and subject line of the email. The toaddrs should be a list of strings. To specify a non-standard SMTP port, use the (host, port) tuple format for the mailhost argument. If you use a string, the standard SMTP port is used. If your SMTP server requires authentication, you can specify a (username, password) tuple for the credentials 自变量。

To specify the use of a secure protocol (TLS), pass in a tuple to the secure argument. This will only be used when authentication credentials are supplied. The tuple should be either an empty tuple, or a single-value tuple with the name of a keyfile, or a 2-value tuple with the names of the keyfile and certificate file. (This tuple is passed to the smtplib.SMTP.starttls() method.)

A timeout can be specified for communication with the SMTP server using the timeout 自变量。

3.3 版改变：添加 timeout 参数。

emit ( record ) ¶: Formats the record and sends it to the specified addressees.

getSubject ( record ) ¶: If you want to specify a subject line which is record-dependent, override this method.

MemoryHandler ¶

The MemoryHandler 类，位于 logging.handlers module, supports buffering of logging records in memory, periodically flushing them to a target handler. Flushing occurs whenever the buffer is full, or when an event of a certain severity or greater is seen.

MemoryHandler is a subclass of the more general BufferingHandler , which is an abstract class. This buffers logging records in memory. Whenever each record is added to the buffer, a check is made by calling shouldFlush() to see if the buffer should be flushed. If it should, then flush() is expected to do the flushing.

class logging.handlers. BufferingHandler ( capacity ) ¶

Initializes the handler with a buffer of the specified capacity. Here, capacity means the number of logging records buffered.

emit ( record ) ¶: Append the record to the buffer. If shouldFlush() returns true, call flush() to process the buffer.

flush ( ) ¶: 对于 BufferingHandler instance, flushing means that it sets the buffer to an empty list. This method can be overwritten to implement more useful flushing behavior.

shouldFlush ( record ) ¶: 返回 True if the buffer is up to capacity. This method can be overridden to implement custom flushing strategies.

class logging.handlers. MemoryHandler ( capacity , flushLevel = ERROR , target = None , flushOnClose = True ) ¶

返回新的实例化 MemoryHandler class. The instance is initialized with a buffer size of capacity (number of records buffered). If flushLevel 未指定， ERROR 源于使用。若无 target is specified, the target will need to be set using setTarget() before this handler does anything useful. If flushOnClose is specified as False , then the buffer is not flushed when the handler is closed. If not specified or specified as True , the previous behaviour of flushing the buffer will occur when the handler is closed.

3.6 版改变： The flushOnClose 参数被添加。

close ( ) ¶: 调用 flush() , sets the target to None and clears the buffer.

flush ( ) ¶: 对于 MemoryHandler instance, flushing means just sending the buffered records to the target, if there is one. The buffer is also cleared when buffered records are sent to the target. Override if you want different behavior.

setTarget ( target ) ¶: Sets the target handler for this handler.

shouldFlush ( record ) ¶: Checks for buffer full or a record at the flushLevel or higher.

HTTPHandler ¶

The HTTPHandler 类，位于 logging.handlers module, supports sending logging messages to a web server, using either GET or POST 语义。

class logging.handlers. HTTPHandler ( host , url , 方法 = 'GET' , secure = False , credentials = None , context = None ) ¶

返回新的实例化 HTTPHandler 类。 host can be of the form host:port , should you need to use a specific port number. If no 方法被指定， GET 被使用。若 secure is true, a HTTPS connection will be used. The context parameter may be set to a ssl.SSLContext instance to configure the SSL settings used for the HTTPS connection. If credentials is specified, it should be a 2-tuple consisting of userid and password, which will be placed in a HTTP ‘Authorization’ header using Basic authentication. If you specify credentials, you should also specify secure=True so that your userid and password are not passed in cleartext across the wire.

3.5 版改变： The context 参数被添加。

mapLogRecord ( record ) ¶: Provides a dictionary, based on record , which is to be URL-encoded and sent to the web server. The default implementation just returns record.__dict__ . This method can be overridden if e.g. only a subset of LogRecord is to be sent to the web server, or if more specific customization of what’s sent to the server is required.

emit ( record ) ¶: Sends the record to the web server as a URL-encoded dictionary. The mapLogRecord() method is used to convert the record to the dictionary to be sent.

注意

Since preparing a record for sending it to a web server is not the same as a generic formatting operation, using setFormatter() to specify a Formatter 对于 HTTPHandler has no effect. Instead of calling format() , this handler calls mapLogRecord() and then urllib.parse.urlencode() to encode the dictionary in a form suitable for sending to a web server.

QueueHandler ¶

Added in version 3.2.

The QueueHandler 类，位于 logging.handlers module, supports sending logging messages to a queue, such as those implemented in the queue or multiprocessing 模块。

Along with the QueueListener class, QueueHandler can be used to let handlers do their work on a separate thread from the one which does the logging. This is important in web applications and also other service applications where threads servicing clients need to respond as quickly as possible, while any potentially slow operations (such as sending an email via SMTPHandler ) are done on a separate thread.

class logging.handlers. QueueHandler ( queue ) ¶

返回新的实例化 QueueHandler class. The instance is initialized with the queue to send messages to. The queue can be any queue-like object; it’s used as-is by the enqueue() method, which needs to know how to send messages to it. The queue is not required to have the task tracking API, which means that you can use SimpleQueue instances for queue .

注意

If you are using multiprocessing , you should avoid using SimpleQueue and instead use multiprocessing.Queue .

emit ( record ) ¶: Enqueues the result of preparing the LogRecord. Should an exception occur (e.g. because a bounded queue has filled up), the handleError() method is called to handle the error. This can result in the record silently being dropped (if logging.raiseExceptions is False ) or a message printed to sys.stderr (若 logging.raiseExceptions is True ).

prepare ( record ) ¶

Prepares a record for queuing. The object returned by this method is enqueued.

The base implementation formats the record to merge the message, arguments, exception and stack information, if present. It also removes unpickleable items from the record in-place. Specifically, it overwrites the record’s msg and message attributes with the merged message (obtained by calling the handler’s format() method), and sets the args , exc_info and exc_text attributes to None .

You might want to override this method if you want to convert the record to a dict or JSON string, or send a modified copy of the record while leaving the original intact.

注意

The base implementation formats the message with arguments, sets the message and msg attributes to the formatted message and sets the args and exc_text attributes to None to allow pickling and to prevent further attempts at formatting. This means that a handler on the QueueListener side won’t have the information to do custom formatting, e.g. of exceptions. You may wish to subclass QueueHandler and override this method to e.g. avoid setting exc_text to None 。注意， message / msg / args changes are related to ensuring the record is pickleable, and you might or might not be able to avoid doing that depending on whether your args are pickleable. (Note that you may have to consider not only your own code but also code in any libraries that you use.)

enqueue ( record ) ¶: Enqueues the record on the queue using put_nowait() ; you may want to override this if you want to use blocking behaviour, or a timeout, or a customized queue implementation.

listener ¶

When created via configuration using dictConfig() , this attribute will contain a QueueListener instance for use with this handler. Otherwise, it will be None .

3.12 版添加。

QueueListener ¶

Added in version 3.2.

The QueueListener 类，位于 logging.handlers module, supports receiving logging messages from a queue, such as those implemented in the queue or multiprocessing modules. The messages are received from a queue in an internal thread and passed, on the same thread, to one or more handlers for processing. While QueueListener is not itself a handler, it is documented here because it works hand-in-hand with QueueHandler .

Along with the QueueHandler class, QueueListener can be used to let handlers do their work on a separate thread from the one which does the logging. This is important in web applications and also other service applications where threads servicing clients need to respond as quickly as possible, while any potentially slow operations (such as sending an email via SMTPHandler ) are done on a separate thread.

class logging.handlers. QueueListener ( queue , * handlers , respect_handler_level = False ) ¶

返回新的实例化 QueueListener class. The instance is initialized with the queue to send messages to and a list of handlers which will handle entries placed on the queue. The queue can be any queue-like object; it’s passed as-is to the dequeue() method, which needs to know how to get messages from it. The queue is not required to have the task tracking API (though it’s used if available), which means that you can use SimpleQueue instances for queue .

注意

If you are using multiprocessing , you should avoid using SimpleQueue and instead use multiprocessing.Queue .

若 respect_handler_level is True , a handler’s level is respected (compared with the level for the message) when deciding whether to pass messages to that handler; otherwise, the behaviour is as in previous Python versions - to always pass each message to each handler.

3.5 版改变： The respect_handler_level 自变量被添加。

dequeue ( block ) ¶

Dequeues a record and return it, optionally blocking.

The base implementation uses get() . You may want to override this method if you want to use timeouts or work with custom queue implementations.

prepare ( record ) ¶

Prepare a record for handling.

This implementation just returns the passed-in record. You may want to override this method if you need to do any custom marshalling or manipulation of the record before passing it to the handlers.

handle ( record ) ¶

Handle a record.

This just loops through the handlers offering them the record to handle. The actual object passed to the handlers is that which is returned from prepare() .

start ( ) ¶

启动监听器。

This starts up a background thread to monitor the queue for LogRecords to process.

stop ( ) ¶

Stops the listener.

This asks the thread to terminate, and then waits for it to do so. Note that if you don’t call this before your application exits, there may be some records still left on the queue, which won’t be processed.

enqueue_sentinel ( ) ¶

Writes a sentinel to the queue to tell the listener to quit. This implementation uses put_nowait() . You may want to override this method if you want to use timeouts or work with custom queue implementations.

Added in version 3.3.

另请参阅

模块 logging: API reference for the logging module.
模块 logging.config: 用于 logging 模块的配置 API。

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logging.handlers — 日志处理程序 ¶

StreamHandler ¶

FileHandler ¶

NullHandler ¶

WatchedFileHandler ¶

BaseRotatingHandler ¶

RotatingFileHandler ¶

TimedRotatingFileHandler ¶

SocketHandler ¶

DatagramHandler ¶

SysLogHandler ¶

NTEventLogHandler ¶

SMTPHandler ¶

MemoryHandler ¶

HTTPHandler ¶

QueueHandler ¶

QueueListener ¶

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`logging.handlers` — 日志处理程序 ¶