Python logging practice

Ten hair 2021-01-20 20:44:17
python logging practice


Log for the development of system development 、 Debugging and running the whole process plays a very important role , During the debugging phase, you need to look at the log to find out what the problem is , In the runtime, if the program crashes , Log can record the cause of program crash . And sometimes python The role of the script is to return text to the caller , At this point, we need to distinguish the return value from the log used for debugging trace . This paper introduces python Common usage .

logging Two ways of log configuration are provided , Simple journal (logging.basicConfig And standard streaming framework

Simple journal

logging.basicConfig Configuration log , Standard output and files are generally supported ( Cannot be configured at the same time )

# -*- coding:utf-8 -*-
import logging
import sys
# Log output to file tenmao.log, Level is INFO, Configure log format and date time format at the same time
#logging.basicConfig(level=logging.INFO,
# format='%(asctime)s %(filename)s %(levelname)s %(message)s',
# datefmt='%a %d %b %Y %H:%M:%S',
# filename='tenmao.log',
# filemode='a')
# Log output to standard error sys.stderr( The default is standard output sys.stdout),filename and stream They are mutually exclusive. , It can't be configured at the same time
logging.basicConfig(level=logging.DEBUG, stream=sys.stderr,
format='%(asctime)s %(filename)s[line:%(lineno)d]%(levelname)s %(message)s')
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')
  • Output log content : tenmao.log
Sat 16 Jan 2021 22:45:28 simple_log.py INFO This is info message
Sat 16 Jan 2021 22:45:28 simple_log.py WARNING This is warning message
Sat 16 Jan 2021 22:45:28 simple_log.py ERROR This is error message
Sat 16 Jan 2021 22:45:28 simple_log.py CRITICAL This is critical message

Standard configuration : Streaming

logging Modules include Logger,Handler,Filter,Formatter Four parts .

  • Logger Recorder , Used to set log collection .
  • Handler processor , Send the log record to the appropriate path .
  • Filter filter , Provides better granularity control , It can decide which logging to output .
  • Formatter formatter , Indicates the format of the log in the final output .
  • Configure sample code
# -*- coding:utf-8 -*-
import logging
# First step , Create a logger
# 1, Create a logger logger
logger = logging.getLogger()
# 2, Set the log level of the logger , The log level here is the lowest level that a logger can record , It's different from the back Handler in setLevel Log level of
logger.setLevel(logging.DEBUG)
# The second step , Create a log processor Handler. Create a Handler, Used to write logs to a file
# 3, Create a Handler, For writing log files , The path of the log file is self-defined
logFile = './log.txt'
fh = logging.FileHandler(logFile, mode='a', encoding='utf-8')
# 4, Set the log level saved to the file
fh.setLevel(logging.INFO)
# The third step , Definition Handler The output format of
# 5, The log output format is defined as follows
format= logging.Formatter('%(asctime)s %(filename)s[line:%(lineno)d] %(levelname)s %(message)s')
# 6, Set up Write to the log file Handler The log format of
fh.setFormatter(format)
# Step four , take Handler Add to the logger logger in
logger.addHandler(fh)
# alike , Create a Handler For console output logs
ch = logging.StreamHandler()
ch.setLevel(logging.INFO)
ch.setFormatter(format)
logger.addHandler(ch)
# Output log
logger.info("This is info message")
logger.warning("This is warning message")
logger.error("This is error message")
logger.critical("This is critical message")

example

  • Abnormal information
try:
raise Exception("hello error")
except Exception as e:
logger.error(" Login error , The reason is :{}".format(e))
logger.error(" Login error ,stack trace", exc_info=True)
else:
logger.info(" Landing successful ...")

exc_info=True You can output the exception stack

The output is as follows

2021-01-16 23:01:42,203 mylog.py[line:35] INFO This is info message
2021-01-16 23:01:42,203 mylog.py[line:36] WARNING This is warning message
2021-01-16 23:01:42,204 mylog.py[line:37] ERROR This is error message
2021-01-16 23:01:42,204 mylog.py[line:38] CRITICAL This is critical message
2021-01-16 23:01:42,204 mylog.py[line:43] ERROR Login error , The reason is :hello error
2021-01-16 23:01:42,204 mylog.py[line:44] ERROR Login error ,stack trace
Traceback (most recent call last):
File "mylog.py", line 41, in <module>
raise Exception("hello error")
Exception: hello error

Reference resources

Participation of this paper Tencent cloud media sharing plan , You are welcome to join us , share .

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