Summary of the use of logging libraries in python

Python's logging module provides a general logging system, which can be used by third-party modules or applications. The following article mainly introduces some knowledge summary about the use of logging library in python. The article gives detailed information. Sample code, friends in need can refer to it, let’s take a look below.

Preface

Recently, due to work needs, I have been writing some python scripts. It feels very low to always use print to print information, so I took the time. I have studied the logging library of python to print and record logs elegantly. I won’t go into more details below, let’s take a look at the detailed introduction.

1. Simply print the log to the screen:

import logging

logging.debug('This is debug message')  #debug
logging.info('This is info message')   #info
logging.warning('This is warning message') #warn

Print on screen ：WARNING:root:This is warning message

By default, WARNING level logs will be printed

• DEBUG: Detailed information , debugging information.

• INFO: Confirm everything is working as expected.

• WARNING: Indicates that something unexpected has occurred, or that a problem will occur in the near future (such as 'disk full'). The software is still working normally.

• ERROR: Due to a more serious problem, the software can no longer perform some functions.

• CRITICAL: A serious error indicating that the software can no longer run.

2. Configure the log input format and method through the basicConfig function

import logging

logging.basicConfig(level=logging.DEBUG,
    format='%(asctime)s %(filename)s[line:%(lineno)d] %(levelname)s %(message)s',
    datefmt='%Y-%m-%d %a %H:%M:%S',
    filename='test.log',
    filemode='w')
 
logging.debug('This is debug message')
logging.info('This is info message')
logging.warning('This is warning message')

The above code will not print the log on the screen, but will generate the log file test.log in the current directory, and the log will be printed in the log file:

2017 -10-16 Mon 10:05:17 testlogging.py[line:25] DEBUG This is debug message

2017-10-16 Mon 10:05:17 testlogging.py[line:26 ] INFO This is info message

2017-10-16 Mon 10:05:17 testlogging.py[line:27] WARNING This is warning message

• ## Parameters of the #logging.basicConfig function:

• filename: Specify the log file name

• #filemode: The same meaning as the file function, specify the log file name Open mode, 'w' or 'a'

##format: Specify the output format and content. format can output a lot of useful information, as shown in the above example:

 %(levelno)s: 打印日志级别的数值
 %(levelname)s: 打印日志级别名称
 %(pathname)s: 打印当前执行程序的路径，其实就是sys.argv[0]
 %(filename)s: 打印当前执行程序名
 %(funcName)s: 打印日志的当前函数
 %(lineno)d: 打印日志的当前行号
 %(asctime)s: 打印日志的时间
 %(thread)d: 打印线程ID
 %(threadName)s: 打印线程名称
 %(process)d: 打印进程ID
 %(message)s: 打印日志信息

datefmt: Specifies the time format, the same as time.strftime()
level: Sets the log level , the default is logging.WARNING
stream: Specify the output stream of the log. You can specify the output to sys.stderr, sys.stdout or a file. The default output is to sys.stderr. When stream When specified with filename at the same time, stream is ignored

3. Output the log to the screen and log file at the same time

#定义一个StreamHandler，将INFO级别或更高的日志信息打印到标准错误，并将其添加到当前的日志处理对象
console = logging.StreamHandler()
console.setLevel(logging.INFO)
formatter = logging.Formatter('%(name)-12s: %(levelname)-8s %(message)s')
console.setFormatter(formatter)
logging.getLogger('').addHandler(console)

Print on the screen:

root: INFO This is info message

root : WARNING This is warning message

printed in the file:

2017-10-16 Mon 10: 20:07 testlogging.py[line:46] DEBUG This is debug message

2017-10-16 Mon 10:20:07 testlogging.py[line:47] INFO This is info message

2017-10-16 Mon 10:20:07 testlogging.py[line:48] WARNING This is warning message

4. Configure through the configuration file Log

#logger.conf
[loggers]
#定义logger模块，root是父类，必需存在的，其它的是自定义。 
keys=root,infoLogger,warnlogger

[logger_root] 
level=DEBUG       #level  级别，级别有DEBUG、INFO、WARNING、ERROR、CRITICAL
handlers=infohandler,warnhandler #handlers 处理类，可以有多个，用逗号分开

[logger_infoLogger]     #[logger_xxxx] logger_模块名称
handlers=infohandler
qualname=infoLogger     #qualname logger名称，应用程序通过 logging.getLogger获取。对于不能获取的名称，则记录到root模块。
propagate=0       #propagate 是否继承父类的log信息，0:否 1:是

[logger_warnlogger]
handlers=warnhandler
qualname=warnlogger
propagate=0

###############################################
#定义handler
[handlers]
keys=infohandler,warnhandler

[handler_infohandler]
class=StreamHandler     #class handler类名
level=INFO       #level 日志级别
formatter=form02      #formatter，下面定义的formatter
args=(sys.stdout,)     #args handler初始化函数参数

[handler_warnhandler]
class=FileHandler
level=WARN
formatter=form01
args=('logs/deploylog.log', 'a')

###############################################
# 定义格式化输出
[formatters]
keys=form01,form02

[formatter_form01]
format=%(message)s %(asctime)s
datefmt=%Y-%m-%d %H:%M:%S

[formatter_form02]
format=%(asctime)s %(levelname)s %(message)s
datefmt=%Y-%m-%d %H:%M:%S

Log format

• ##%(filename)s file name, excluding directory

• %(pathname)s Directory name, full path

• %(funcName)s Function name

• %(levelname) s level name

• %(lineno)d line number

• ##%(module)s module name

• %(message)s Message body

• %(name)s Log module name

• %(process)d Process id

• %(processName)s process name

• %(thread)d thread id

• % (threadName)s thread name

• Test configuration file

from logging.config import fileConfig

fileConfig('logger.conf')
logger=logging.getLogger('infoLogger')
logger.info('test1')
logger_error=logging.getLogger('warnhandler')
logger_error.warn('test5')

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