Answers for "python logging library"

python logging to file

import logging
import sys

logger = logging.getLogger()
logger.setLevel(logging.INFO)
formatter = logging.Formatter('%(asctime)s | %(levelname)s | %(message)s', 
                              '%m-%d-%Y %H:%M:%S')

stdout_handler = logging.StreamHandler(sys.stdout)
stdout_handler.setLevel(logging.DEBUG)
stdout_handler.setFormatter(formatter)

file_handler = logging.FileHandler('logs.log')
file_handler.setLevel(logging.DEBUG)
file_handler.setFormatter(formatter)

logger.addHandler(file_handler)
logger.addHandler(stdout_handler)

python logging to file

import logging

"""
DEBUG
INFO
WARNING
ERROR
CRITICAL
"""
# asctime: time of the log was printed out
# levelname: name of the log
# datefmt: format the time of the log
# give DEBUG log
logging.basicConfig(format='%(asctime)s %(levelname)-8s [%(filename)s:%(lineno)d] %(message)s',
    datefmt='%d-%m-%Y:%H:%M:%S',
    level=logging.DEBUG,
    filename='logs.txt')

logger = logging.getLogger('my_app')

logger.debug("This is a debug log")
logger.info("This is an info log")
logger.critical("This is critical")
logger.error("An error occurred")

python log file

import logging
logging.basicConfig(filename='example.log', encoding='utf-8', level=logging.DEBUG)
logging.debug('This message should go to the log file')
logging.info('So should this')
logging.warning('And this, too')
logging.error('And non-ASCII stuff, too, like Øresund and Malmö')

logging.logger

import logging

logging.basicConfig(level=logging.WARNING)
logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)
  
logger.debug("some debugging...")
logger.error("some error...")

python logging basiclogging rotatingfilehandler

import logging

rfh = logging.handlers.RotatingFileHandler(
 	filename='foo.log', 
  	mode='a',
  	maxBytes=20*1024*1024,
  	backupCount=2,
  	encoding=None,
  	delay=0
)

logging.basicConfig(
  	level=logging.DEBUG,
  	format="%(asctime)s %(name)-25s %(levelname)-8s %(message)s",
    datefmt="%y-%m-%d %H:%M:%S",
    handlers=[
    	rfh
    ]
)

logger = logging.getLogger('main')

logger.debug("test")

testing logging python

# can be done by using unittest's assertLogs

from unittest import TestCase

class MyTest(TestCase):
  
  def test_logs(self):
    with self.assertLogs('foo', level='INFO') as cm:
        logging.getLogger('foo').info('first message')
        logging.getLogger('foo.bar').error('second message')
        self.assertEqual(cm.output, ['INFO:foo:first message',
                                 'ERROR:foo.bar:second message'])