logging模块

什么时候使用logging

Task you want to perform	The best tool for the task
Display console output for ordinary usage of a command line script or program	print()
Report events that occur during normal operation of a program (e.g. for status monitoring or fault investigation)	logging.info() (or logging.debug() for very detailed output for diagnostic purposes)
Issue a warning regarding a particular runtime event	warnings.warn() in library code if the issue is avoidable and the client application should be modified to eliminate the warninglogging.warning() if there is nothing the client application can do about the situation, but the event should still be noted
Report an error regarding a particular runtime event	Raise an exception
Report suppression of an error without raising an exception (e.g. error handler in a long-running server process)	logging.error(), logging.exception() or logging.critical() as appropriate for the specific error and application domain

级别

Level	When it’s used	Numeric value
DEBUG	Detailed information, typically of interest only when diagnosing problems.	10
INFO	Confirmation that things are working as expected.	20
WARNING	An indication that something unexpected happened, or indicative of some problem in the near future (e.g. ‘disk space low’). The software is still working as expected.	30
ERROR	Due to a more serious problem, the software has not been able to perform some function.	40
CRITICAL	A serious error, indicating that the program itself may be unable to continue running.	50
NOTSET		0

基本用法

代码

import logging

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

输出

WARNING:root:This is warning message
ERROR:root:This is error message
CRITICAL:root:This is critical message

注意

• DEBUG和INFO级别日志没有在控制台显示, 是因为默认级别是WARNING

保存到文件

代码

import logging

logging.basicConfig(filename='example.log',level=logging.DEBUG)        # 设置日志路径及文件名 和 记录日志的级别
logging.debug('This message should go to the log file')
logging.info('So should this')
logging.warning('And this, too')

输出

example.log内的内容

DEBUG:root:This message should go to the log file
INFO:root:So should this
WARNING:root:And this, too