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python logging 重复写日志问题

程序员文章站 2023-08-22 22:45:25
原文链接:https://blog.csdn.net/huilan_same/article/details/51858817 ......

原文链接:https://blog.csdn.net/huilan_same/article/details/51858817 

在用logging模块写日志的时候,遇到了日志重复打印的问题。即在同一个脚本中第一次调用,正常显示,第二次调用,则显示了重复的两条,以此类推,非常头疼。

网上找到原因:没有删除前一次调用的handle对象

示例

import logging


def log(message):
    logger = logging.getLogger('testlog')

    streamhandler = logging.StreamHandler()
    streamhandler.setLevel(logging.ERROR)
    formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(name)s - %(message)s')
    streamhandler.setFormatter(formatter)

    logger.addHandler(streamhandler)
    logger.error(message)

if __name__ == '__main__':
    log('hi')
    log('hi too')
    log('hi three')

输出结果:

2016-07-08 09:17:29,740 - ERROR - testlog - hi 
2016-07-08 09:17:29,740 - ERROR - testlog - hi too 
2016-07-08 09:17:29,740 - ERROR - testlog - hi too 
2016-07-08 09:17:29,740 - ERROR - testlog - hi three 
2016-07-08 09:17:29,740 - ERROR - testlog - hi three 
2016-07-08 09:17:29,740 - ERROR - testlog - hi three

 

修改后的代码:

import logging


def log(message):
    logger = logging.getLogger('testlog')

    streamhandler = logging.StreamHandler()
    streamhandler.setLevel(logging.ERROR)
    formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(name)s - %(message)s')
    streamhandler.setFormatter(formatter)

    logger.addHandler(streamhandler)
    logger.error(message)

    #  添加下面一句,在记录日志之后移除句柄
    logger.removeHandler(streamhandler)

if __name__ == '__main__':
    log('hi')
    log('hi too')
    log('hi three')

修改后显示结果:

2016-07-08 09:32:28,206 - ERROR - testlog - hi 
2016-07-08 09:32:28,206 - ERROR - testlog - hi too 
2016-07-08 09:32:28,206 - ERROR - testlog - hi three

深度解析

第二次调用log的时候,根据getLogger(name)里的name获取一个logger对象,而这个logger对象里已经有了第一次添加的handler,第二次又添加了一个handler,所以logger对象里有两个相同的handler,以此类推,调用几次就有几个handler。

 

解决方法:1.每次调用都修改getLogger(name) 中的name

                  2.使用removeHandler(handlername)

                  3.在log方法里做判断,是否已经存在handler

                  4.使用pop函数把handle列表中的handler删除

 

方法三:

import logging


def log(message):
    logger = logging.getLogger('testlog')

    #  这里进行判断,如果logger.handlers列表为空,则添加,否则,直接去写日志
    if not logger.handlers:
        streamhandler = logging.StreamHandler()
        streamhandler.setLevel(logging.ERROR)
        formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(name)s - %(message)s')
        streamhandler.setFormatter(formatter)
        logger.addHandler(streamhandler)

    logger.error(message)


if __name__ == '__main__':
    log('hi')
    log('hi too')
    log('hi three')

方法四:

import logging


def log(message):
    logger = logging.getLogger('testlog')

    streamhandler = logging.StreamHandler()
    streamhandler.setLevel(logging.ERROR)
    formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(name)s - %(message)s')
    streamhandler.setFormatter(formatter)

    logger.addHandler(streamhandler)

    logger.error(message)

    #  用pop方法把logger.handlers列表中的handler移除,注意如果你add了多个handler,这里需多次pop,或者可以直接为handlers列表赋空值
    logger.handlers.pop()
    # logger.handler = []


if __name__ == '__main__':
    log('hi')
    log('hi too')
    log('hi three')