Python Logging module research

Background

I added a logging function to a new project and wanted to write one myself, but by chance, I discovered through Google that Python has a very powerful built-in log module: logging. After some rough research, here are some of my notes.

Why use logs

Track some running information of the program to achieve the purpose of always understanding the running status of the program, quickly catching program exceptions, and timely discovering program errors

Introduction to the logging module

Starting from Python 2.3, Python The standard library has added a logging module. The logging module provides a standard information output interface for running applications. The typical logging mechanism implementation is to simply write the data to be output to a txt file. The way to write a log file is A common way of logging, and the logging module provides more. It can output output information to all file-like objects, even TCP and UDP sockets, email servers, Unix syslog systems, and NT series Event log system, memory buffer and HTTP server, and of course "real" files.

Introducing the logging module:

import logging #import logging module
#使用logging模块：
class CLog:
   #----------------------------------------------------------------------------
   def __init__(self):
      self.logger = logging.getLogger()
      fileHandler = logging.FileHandler(LOG_FILE_PATH)
      formatHandler = logging.Formatter('%(asctime)s %(levelname)s: %(message)s')
      fileHandler.setFormatter(formatHandler)
      self.logger.addHandler(fileHandler)
      self.logger.setLevel(logging.NOTSET)
   
   #----------------------------------------------------------------------------
   def DebugMessage(self,msg):
      self.logger.debug(msg)
      pass
      
oCLog = CLog()

A simple log module is defined above, and I want to use this simple code to describe it Check the logging module

logger

to get an instance of the log. This part of the code is well separated. You can enrich the characteristics of the log instance by adding different handlers

FileHandler

specifies that the output end of the Log is a file, through Pass in the file path to specify the output file. We can define other output terminals for Log, such as StreamHandler, and various other complex output methods. File is probably the most commonly used method, and other methods need to be slowly explored

FormatHandler

FomartHandler specifies the output format of FileHandler. For example, I use the following format: ('%(asctime)s %(levelname)s: %(message)s'), then the output text format is:

2013-07 -25 08:20:01,525 INFO: goodbye [127.0.0.1]:60442

For format keywords, such as asctime, levelname, please refer to the LogRecord attributes official document

Level

The Logging module defines 5 types of log information The priority of

LevelWhen it's used

DEBUGDetailed information, typically of interest only when diagnosing problems.

INFOConfirmation that things are working as expected.

WARNINGAn 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.

ERRORDue to a more serious problem, the software has not been able to perform some function.

CRITICALA serious error, indicating that the program itself may be unable to continue running.

Priority relationship:

DEBUG

You can determine the output information based on self.logger.debug(msg), self.logger.info(msg), and other functions Priority

SetLevel

SetLevel function defines the priority of the Log instance for processing log information. If the defined priority is info, all debug information will be ignored and will not be output to the output. Only the set priority will be input. And information above the set priority