Python logging details

ztenv 2020-11-17 21:02:32
python logging details

The level of logging

import logging # introduce logging modular 
# Print the information to the console 

The echo :
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As you can see on the top, only the last three can be printed

Default generated root logger Of level yes logging.WARNING, Below this level, it will not output


  1. debug : Print all the logs , Details , It's usually only a diagnostic problem

  2. info : Print info,warning,error,critical Level of logging , Make sure everything works as expected

  3. warning : Print warning,error,critical Level of logging , A sign that , Something unexpected happened , Or show some problems in the near future ( for example . Low disk space ”), The software works as expected

  4. error : Print error,critical Level of logging , More serious problem , The software doesn't perform some functions

  5. critical : Print critical Level , A serious mistake , This indicates that the program itself may not continue to run

Now , If you need to display below WARNING Level content , Can be introduced NOTSET Level :

import logging # introduce logging modular 
logging.basicConfig(level=logging.NOTSET) # Set the log level 
logging.debug("print all levels log")

The echo :
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Explanation of some terms

  1. Logging.Formatter: This class configures the format of the log , Customize the date and time in it , The output log will display the content according to the set format .

  2. Logging.Logger:Logger yes Logging The body of the module , To carry out the following three tasks :

    • Provides the program with an interface for logging
    • Determine the level of the log , And determine whether to filter
    • Distribute this log to different handler
  3. Common functions are :

    • Logger.setLevel() Set the log level
    • Logger.addHandler() and Logger.removeHandler() Add and remove a Handler
    • Logger.addFilter() Add one Filter, Filtration
    • Logging.Handler:Handler Distribute logs based on log level , If set to WARNING Grade Handler Only deal with WARNING And above .
    • setLevel() Set level
    • setFormatter() Set up Formatter

Log output - Console

import logging # introduce logging modular 
logging.basicConfig(level=logging.DEBUG,format='%(asctime)s-%(filename)s%(funcName)s(%(lineno)d)[%(thread)d]-[%(levelname)s]%(message)s') # Since the level in the basic log configuration is set to DEBUG, So the print information will be displayed on the console 

The above code passes logging.basicConfig Function to configure the log level and log content output format ; Because the level is DEBUG, So will DEBUG Information above the level is output and displayed on the console .

The echo :
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Log output - file

import logging # introduce logging modular 
import os.path
import time
# First step , Create a logger
logger = logging.getLogger()
logger.setLevel(logging.INFO) # Log Grade master switch 
# The second step , Create a handler, For writing log files 
rq = time.strftime('%Y%m%d%H%M', time.localtime(time.time()))
log_path = os.path.dirname(os.getcwd()) + '/Logs/'
log_name = log_path + rq + '.log'
logfile = log_name
fh = logging.FileHandler(logfile, mode='w')
fh.setLevel(logging.DEBUG) # Output to file Of log Level switch 
# The third step , Definition handler The output format of 
formatter = logging.Formatter("%(asctime)s - %(filename)s[line:%(lineno)d] - %(levelname)s: %(message)s")
# Step four , take logger Add to handler Inside 
# journal 
logger.debug('this is a logger debug message')'this is a logger info message')
logger.warning('this is a logger warning message')
logger.error('this is a logger error message')
logger.critical('this is a logger critical message')

Log output - Console and files

# Just insert a handler Output to console :
# Create a handler, For output to console 
ch = logging.StreamHandler()
ch.setLevel(logging.WARNING) # Output to console Of log Level switch 

format Common format description

%(levelno)s: Print log level values
%(levelname)s: Print log level name
%(pathname)s: Print the path of the currently executing program , In fact, that is sys.argv[0]
%(filename)s: Print the name of the currently executing program
%(funcName)s: Print the current function of the log
%(lineno)d: Print the current line number of the log
%(asctime)s: Time to print the log
%(thread)d: Print thread ID
%(threadName)s: Print thread name
%(process)d: Printing process ID
%(message)s: Print log information

The catching , use traceback Record

import os.path
import time
import logging
# Create a logger
logger = logging.getLogger()
logger.setLevel(logging.INFO) # Log Grade master switch 
# Create a handler, For writing log files 
rq = time.strftime('%Y%m%d%H%M', time.localtime(time.time()))
log_path = os.path.dirname(os.getcwd()) + '/Logs/'
log_name = log_path + rq + '.log'
logfile = log_name
fh = logging.FileHandler(logfile, mode='w')
fh.setLevel(logging.DEBUG) # Output to file Of log Level switch 
# Definition handler The output format of 
formatter = logging.Formatter("%(asctime)s - %(filename)s[line:%(lineno)d] - %(levelname)s: %(message)s")
# Use logger.XX To record errors , there "error" It can be modified according to the required level 
open('/path/to/does/not/exist', 'rb')
except (SystemExit, KeyboardInterrupt):
except Exception, e:
logger.error('Failed to open file', exc_info=True)

If you need to report no errors in the log , Record only , Can be exc_info=False, Echo as follows :

Log scrolling and expired deletion ( By time

import logging
import time
import re
from logging.handlers import TimedRotatingFileHandler
from logging.handlers import RotatingFileHandler
def backroll():
# Log print format 
log_fmt = '%(asctime)s\tFile \"%(filename)s\",line %(lineno)s\t%(levelname)s: %(message)s'
formatter = logging.Formatter(log_fmt)
# establish TimedRotatingFileHandler object 
log_file_handler = TimedRotatingFileHandler(filename="ds_update", when="M", interval=2, backupCount=2)
#log_file_handler.suffix = "%Y-%m-%d_%H-%M.log"
#log_file_handler.extMatch = re.compile(r"^\d{4}-\d{2}-\d{2}_\d{2}-\d{2}.log$")
log = logging.getLogger()
# Circular printing log 
log_content = "test log"
count = 0
while count < 30:
count = count + 1
if __name__ == "__main__":

filename: Log file name prefix;

when: Is a string , The basic unit used to describe the rolling period , The values and meanings of a string are as follows :
“S”: Seconds
“M”: Minutes
“H”: Hours
“D”: Days
“W”: Week day (0=Monday)
“midnight”: Roll over at midnight

interval: Rolling cycle , The unit has when Appoint , such as :when=’D’,interval=1, A log file is generated every day

backupCount: Indicates the number of reserved log files


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