Python学习之logging模块

Python自带日志处理模块logging
默认的日志级别有DEBUG,INFO,WARNING,ERROR,CRITICAL，对应的函数是debug(),info(),warning(),error()和critical()

In [490]: import logging

In [491]: LOG_FILENAME='/tmp/example.log'

In [492]: logging.basicConfig(filename=LOG_FILENAME,level=logging.DEBUG)

In [493]: logging.debug('This message should go to the log file')

查看/tmp/example.log的内容

$ cat /tmp/example.log
DEBUG:root:This message should go to the log file

不断执行

logging.debug('This message should go to the log file')

/tmp/example.log会不断地刷新

日志轮转

In [639]: import glob

In [640]: import logging

In [641]: import logging.handlers

In [642]: LOG_FILENAME='/tmp/logging_rotatingfile_example.out'

In [643]: my_logger=logging.getLogger('MyLogger')

In [644]: my_logger.setLevel(logging.DEBUG)

In [645]: handler=logging.handlers.RotatingFileHandler(LOG_FILENAME,maxBytes=20,backupCount=5)

In [646]: my_logger.addHandler(handler)

In [648]: for i in range(20):
my_logger.debug('i=%d' % i)
.....:
.....:

In [650]: logfiles=glob.glob('%s*' %LOG_FILENAME)

In [651]: for filename in logfiles:
.....:     print filename
.....:
.....:
/tmp/logging_rotatingfile_example.out.1
/tmp/logging_rotatingfile_example.out.2
/tmp/logging_rotatingfile_example.out.5
/tmp/logging_rotatingfile_example.out.3
/tmp/logging_rotatingfile_example.out.4
/tmp/logging_rotatingfile_example.out

最近的日志文件总是名为logging_rotatingfile_example.out，一旦大小达到maxBytes设置的20字节，就将轮转。

logging模块最重要的一个功能就是可以根据设置的不同的日志级别输出不同的日志信息。

import logging
import sys

LEVELS={'debug':logging.DEBUG,
'info' :logging.INFO,
'warning':logging.WARNING,
'error':logging.ERROR,
'critical':logging.CRITICAL
}

if sys.argv > 1:
level_name = sys.argv[1]
level=LEVELS.get(level_name,logging.NOTSET)
logging.basicConfig(level=level)

logging.debug('This is a debug message')
logging.info('This is a info message')
logging.warning('This is a warning message')
logging.error('This is a error message')
logging.critical('This is a critical error message')
~
~

$ python logging_level_example.py debug
DEBUG:root:This is a debug message
INFO:root:This is a info message
WARNING:root:This is a warning message
ERROR:root:This is a error message
CRITICAL:root:This is a critical error message

$ python logging_level_example.py info
INFO:root:This is a info message
WARNING:root:This is a warning message
ERROR:root:This is a error message
CRITICAL:root:This is a critical error message

$ python logging_level_example.py warning
WARNING:root:This is a warning message
ERROR:root:This is a error message
CRITICAL:root:This is a critical error message

$ python logging_level_example.py error
ERROR:root:This is a error message
CRITICAL:root:This is a critical error message

$ python logging_level_example.py critical
CRITICAL:root:This is a critical error message

logging模块包括logger，handler，filter和formatter。
Logger.setLevel()设置日志级别

Logger.addFilter()
Logger.removeFilter()
Logger.debug()
Logger.info()
Logger.warning()
Logger.error()
Logger.critical()
Logger.exception()
Logger.log()

logging.Formatter
定义日志格式
%(name)s Name of the logger (logging channel)
| %(levelno)s Numeric logging level for the message (DEBUG, INFO,
| WARNING, ERROR, CRITICAL)
| %(levelname)s Text logging level for the message ("DEBUG", "INFO",
| "WARNING", "ERROR", "CRITICAL")
| %(pathname)s Full pathname of the source file where the logging
| call was issued (if available)
| %(filename)s Filename portion of pathname
| %(module)s Module (name portion of filename)
| %(lineno)d Source line number where the logging call was issued
| (if available)
| %(funcName)s Function name
| %(created)f Time when the LogRecord was created (time.time()
| return value)
| %(asctime)s Textual time when the LogRecord was created
| %(msecs)d Millisecond portion of the creation time
| %(relativeCreated)d Time in milliseconds when the LogRecord was created,
| relative to the time the logging module was loaded
| (typically at application startup time)
| %(thread)d Thread ID (if available)
| %(threadName)s Thread name (if available)
| %(process)d Process ID (if available)
| %(message)s The result of record.getMessage(), computed just as
| the record is emitted

案例程序

def info(str):
logger=logging.getLogger('test')
FileHandler=logging.FileHandler('/tmp/'+'2015-06-26'+'.log')
FileHandler.setFormatter(logging.Formatter('%(asctime)s %(levelname)s %(message)s'))
logger.addHandler(FileHandler)
logger.setLevel(logging.INFO)
logger.info(str)
logger.removeHandler(FileHandler)
FileHandler.close()

def error(str):
logger=logging.getLogger('test')
FileHandler=logging.FileHandler('/tmp/'+'2015-06-26'+'.log')
FileHandler.setFormatter(logging.Formatter('%(asctime)s %(levelname)s %(message)s'))
logger.addHandler(FileHandler)
logger.setLevel(logging.ERROR)
logger.error(str)
logger.removeHandler(FileHandler)
FileHandler.close()

info('Starting agent process')
error('Starting error')

输出结果

2015-06-26 22:31:10,489 INFO Starting agent process
2015-06-26 22:31:10,489 ERROR Starting error
2015-06-26 22:31:12,961 INFO Starting agent process
2015-06-26 22:31:12,961 ERROR Starting error
2015-06-26 22:31:13,709 INFO Starting agent process
2015-06-26 22:31:13,709 ERROR Starting error
2015-06-26 22:31:14,201 INFO Starting agent process
2015-06-26 22:31:14,201 ERROR Starting error
2015-06-26 22:31:14,626 INFO Starting agent process
2015-06-26 22:31:14,626 ERROR Starting error
2015-06-26 22:31:15,032 INFO Starting agent process
2015-06-26 22:31:15,032 ERROR Starting error
2015-06-26 22:31:15,455 INFO Starting agent process
2015-06-26 22:31:15,455 ERROR Starting error
2015-06-26 22:31:16,500 INFO Starting agent process
2015-06-26 22:31:16,500 ERROR Starting error
2015-06-26 22:31:17,100 INFO Starting agent process
2015-06-26 22:31:17,100 ERROR Starting error
2015-06-26 22:31:17,536 INFO Starting agent process
2015-06-26 22:31:17,536 ERROR Starting error

参考文档：
https://docs.python.org/2.6/library/logging.html#configuration-file-format

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