Python logging模块学习笔记

模块级函数

logging.getlogger([name]):返回一个logger对象，如果没有指定名字将返回root logger
logging.debug()、logging.info()、logging.warning()、logging.error()、logging.critical()：设定root logger的日志级别
logging.basicconfig():用默认formatter为日志系统建立一个streamhandler，设置基础配置并加到root logger中

示例：logging_level_example.py

import logging
import sys

levels = {'debug': logging.debug,
          'info': logging.info,
          'warning': logging.warning,
          'error': logging.error,
          'critical': logging.critical}

if len(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 an info message')
logging.warning('this is a warning message')
logging.error('this is an error message')
logging.critical('this is a critical error message')

输出：

$ python logging_level_example.py debug
debug:root:this is a debug message
info:root:this is an info message
warning:root:this is a warning message
error:root:this is an error message
critical:root:this is a critical error message

$ python logging_level_example.py info
info:root:this is an info message
warning:root:this is a warning message
error:root:this is an error message
critical:root:this is a critical error message

loggers

logger.setlevel(lel):指定最低的日志级别，低于lel的级别将被忽略。debug是最低的内置级别，critical为最高
logger.addfilter(filt)、logger.removefilter(filt):添加或删除指定的filter
logger.addhandler(hdlr)、logger.removehandler(hdlr)：增加或删除指定的handler
logger.debug()、logger.info()、logger.warning()、logger.error()、logger.critical()：可以设置的日志级别

示例：simple_logging_module.py

import logging

# create logger
logger = logging.getlogger("simple_example")
logger.setlevel(logging.debug)

# create console handler and set level to debug
ch = logging.streamhandler()
ch.setlevel(logging.debug)

# create formatter
formatter = logging.formatter("%(asctime)s - %(name)s - %(levelname)s - %(message)s")

# add formatter to ch
ch.setformatter(formatter)

# add ch to logger
logger.addhandler(ch)

# "application" code
logger.debug("debug message")
logger.info("info message")
logger.warn("warn message")
logger.error("error message")
logger.critical("critical message")

输出：

$ python simple_logging_module.py
2005-03-19 15:10:26,618 - simple_example - debug - debug message
2005-03-19 15:10:26,620 - simple_example - info - info message
2005-03-19 15:10:26,695 - simple_example - warning - warn message
2005-03-19 15:10:26,697 - simple_example - error - error message
2005-03-19 15:10:26,773 - simple_example - critical - critical message

handlers

handler对象负责发送相关的信息到指定目的地。可以通过addhandler()方法添加多个多handler
handler.setlevel(lel):指定被处理的信息级别，低于lel级别的信息将被忽略
handler.setformatter()：给这个handler选择一个格式
handler.addfilter(filt)、handler.removefilter(filt)：新增或删除一个filter对象

formatters

formatter对象设置日志信息最后的规则、结构和内容，默认的时间格式为%y-%m-%d %h:%m:%s，下面是formatter常用的一些信息

%(name)s	logger的名字
%(levelno)s	数字形式的日志级别
%(levelname)s	文本形式的日志级别
%(pathname)s	调用日志输出函数的模块的完整路径名，可能没有
%(filename)s	调用日志输出函数的模块的文件名
%(module)s	调用日志输出函数的模块名
%(funcname)s	调用日志输出函数的函数名
%(lineno)d	调用日志输出函数的语句所在的代码行
%(created)f	当前时间，用unix标准的表示时间的浮 点数表示
%(relativecreated)d	输出日志信息时的，自logger创建以 来的毫秒数
%(asctime)s	字符串形式的当前时间。默认格式是 “2003-07-08 16:49:45,896”。逗号后面的是毫秒
%(thread)d	线程id。可能没有
%(threadname)s	线程名。可能没有
%(process)d	进程id。可能没有
%(message)s	用户输出的消息

最后来个完整例子：

import logging

# set up logging to file - see previous section for more details
logging.basicconfig(level=logging.debug,
                    format='%(asctime)s %(name)-12s %(levelname)-8s %(message)s',
                    datefmt='%m-%d %h:%m',
                    filename='/temp/myapp.log',
                    filemode='w')
# define a handler which writes info messages or higher to the sys.stderr
console = logging.streamhandler()
console.setlevel(logging.info)
# set a format which is simpler for console use
formatter = logging.formatter('%(name)-12s: %(levelname)-8s %(message)s')
# tell the handler to use this format
console.setformatter(formatter)
# add the handler to the root logger
logging.getlogger('').addhandler(console)

# now, we can log to the root logger, or any other logger. first the root...
logging.info('jackdaws love my big sphinx of quartz.')

# now, define a couple of other loggers which might represent areas in your
# application:

logger1 = logging.getlogger('myapp.area1')
logger2 = logging.getlogger('myapp.area2')

logger1.debug('quick zephyrs blow, vexing daft jim.')
logger1.info('how quickly daft jumping zebras vex.')
logger2.warning('jail zesty vixen who grabbed pay from quack.')
logger2.error('the five boxing wizards jump quickly.')

运行后，在终端看到的结果

root        : info     jackdaws love my big sphinx of quartz.
myapp.area1 : info     how quickly daft jumping zebras vex.
myapp.area2 : warning  jail zesty vixen who grabbed pay from quack.
myapp.area2 : error    the five boxing wizards jump quickly.

在日志文件中的结果

10-22 22:19 root         info     jackdaws love my big sphinx of quartz.
10-22 22:19 myapp.area1  debug    quick zephyrs blow, vexing daft jim.
10-22 22:19 myapp.area1  info     how quickly daft jumping zebras vex.
10-22 22:19 myapp.area2  warning  jail zesty vixen who grabbed pay from quack.
10-22 22:19 myapp.area2  error    the five boxing wizards jump quickly.

发现debug信息只有在文件中出现，这是因为streamhandler中setlevel是info，可以看出logger.setlevel()和handler.setlevel()的区别

详细信息请参阅 http://docs.python.org/library/logging.html