A logger is configured to have a log level. This log level describes the severity of the messages that the logger will handle. Python defines the following log levels:
§ DEBUG: Low level system information for debugging purposes
§ INFO: General system information
§ WARNING: Information describing a minor problem that has occurred.
§ ERROR: Information describing a major problem that has occurred.
§ CRITICAL: Information describing a critical problem that has occurred.
Each message that is written to the logger is a Log Record. Each log record also has a log level indicating the severity of that specific message. A log record can also contain useful metadata that describes the event that is being logged. This can include details such as a stack trace or an error code.
When a message is given to the logger, the log level of the message is compared to the log level of the logger. If the log level of the message meets or exceeds the log level of the logger itself, the message will undergo further processing. If it doesn’t, the message will be ignored.
Once a logger has determined that a message needs to be processed, it is passed to a Handler.
（来源：https://docs.djangoproject.com/en/1.4/topics/logging/ ）
简单的范例
#-*- coding: utf-8 -*-
import logging
"""logging的简单使用示例
"""
if __name__ == '__main__':
# 最简单的用法，不推荐直接用logging模块
logging.debug(u'这个不会被打印出来')
logging.info(u'这个也不会被打印出来')
logging.warning(u'这个就会了，因为logging默认的级别是WARNING，低于这个等级的信息就会被忽略')
稍微难一点的范例
#-*- coding: utf-8 -*-
import logging
"""logging的使用示例
"""
if __name__ == '__main__':
# python官方文档中提供的一段示例，使用logging模块产生logger对象
FORMAT = '%(asctime)-15s %(clientip)s %(user)-8s %(message)s'
logging.basicConfig(format = FORMAT)
d = { 'clientip' : '192.168.0.1', 'user' : 'fbloggs' }
# 创建一个日志对象
logger = logging.getLogger('tcpserver')
logger.warning('Protocol problem: %s', 'connection reset', extra = d)
# 设置级别
logger.setLevel(logging.DEBUG)
logger.debug('Hello', extra = d)
复杂一点的用法，为logger添加了若干个handler。
#-*- coding: utf-8 -*-
import logging, logging.config
"""logging的使用示例
"""
if __name__ == '__main__':
# 比较复杂的用法
LOGGING = {
# 版本，总是1
'version': 1,
'disable_existing_loggers': True,
'formatters': {
'verbose': {'format': '%(levelname)s %(asctime)s %(module)s %(process)d %(thread)d %(message)s'},
'simple': {'format': '%(levelname)s %(message)s'},
'default': {
'format' : '%(asctime)s %(message)s',
'datefmt' : '%Y-%m-%d %H:%M:%S'
}
},
'handlers': {
'null': {
'level':'DEBUG',
'class':'logging.NullHandler',
},
'console':{
'level':'DEBUG',
'class':'logging.StreamHandler',
'formatter': 'default'
},
'file': {
'level': 'INFO',
# TimedRotatingFileHandler会将日志按一定时间间隔写入文件中，并
# 将文件重命名为'原文件名+时间戮'这样的形式
# Python提供了其它的handler，参考logging.handlers
'class': 'logging.handlers.TimedRotatingFileHandler',
'formatter': 'default',
# 后面这些会以参数的形式传递给TimedRotatingFileHandler的
# 构造器
# filename所在的目录要确保存在
'filename' : 'log',
# 每5分钟刷新一下
'when' : 'M',
'interval' : 1,
'encoding' : 'utf8',
}
},
'loggers' : {
# 定义了一个logger
'mylogger' : {
'level' : 'DEBUG',
'handlers' : ['console', 'file'],
'propagate' : True
}
}
}
logging.config.dictConfig(LOGGING)
logger = logging.getLogger('mylogger')
logger.info('Hello')
另外，还可以通过配置文件来配置logging，方法如下：
配置文件（log_conf）：
[loggers]
keys=root,mylogger
[handlers]
keys=null,console,file
[formatters]
keys=verbose,simple,default
[formatter_verbose]
format=%(levelname)s %(asctime)s %(module)s %(process)d %(thread)d %(message)s
datefmt=
class=logging.Formatter
[formatter_simple]
format=%(levelname)s %(message)s
datefmt=
class=logging.Formatter
[formatter_default]
format=%(asctime)s %(message)s
datefmt=%Y-%m-%d %H:%M:%S
class=logging.Formatter
[logger_mylogger]
level=DEBUG
handlers=console,file
propagate=1
qualname=
[logger_root]
level=NOTSET
handlers=
[handler_null]
class=NullHandler
level=DEBUG
args=()
[handler_console]
class=StreamHandler
level=DEBUG
args=()
[handler_file]
class=handlers.TimedRotatingFileHandler
level=INFO
formatter=default
args=('log','M',1,0,'utf8')
Python代码：
#-*- coding: utf-8 -*-
import logging, logging.config
"""logging的使用示例
"""
if __name__ == '__main__':
# 使用配置文件
logging.config.fileConfig('log_conf')
logger = logging.getLogger('mylogger')
logger.info('Hello')