python logging level code example

Example 1: 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)

Example 2: 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")

Example 3: python logging example

# logging_example.py

import logging

# Create a custom logger
logger = logging.getLogger(__name__)

# Create handlers
c_handler = logging.StreamHandler()
f_handler = logging.FileHandler('file.log')
c_handler.setLevel(logging.WARNING)
f_handler.setLevel(logging.ERROR)

# Create formatters and add it to handlers
c_format = logging.Formatter('%(name)s - %(levelname)s - %(message)s')
f_format = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
c_handler.setFormatter(c_format)
f_handler.setFormatter(f_format)

# Add handlers to the logger
logger.addHandler(c_handler)
logger.addHandler(f_handler)

logger.warning('This is a warning')
logger.error('This is an error')

Example 4: 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...")

Example 5: from logging import logger

#!/usr/bin/env python3
# -*- coding: UTF-8 -*-

import logging

logger = logging.getLogger(__name__)
logging.basicConfig(level=logging.DEBUG)

logger.debug('Loging %s lewel', 'DEBUG')
logger.info('Loging %s lewel', 'INFO')
logger.warning('Loging %s lewel', 'WARN')
logger.error('Loging %s lewel', 'ERROR')
logger.critical('Loging %s lewel', 'CRITICAL')

Example 6: pythong logging logger to string

import logging
try:
    from cStringIO import StringIO      # Python 2
except ImportError:
    from io import StringIO

class LevelFilter(logging.Filter):
    def __init__(self, levels):
        self.levels = levels

    def filter(self, record):
        return record.levelno in self.levels

log_stream = StringIO()    
logging.basicConfig(stream=log_stream, level=logging.NOTSET)
logging.getLogger().addFilter(LevelFilter((logging.INFO, logging.WARNING, logging.ERROR)))

logging.info('hello world')
logging.warning('be careful!')
logging.debug("you won't see this")
logging.error('you will see this')
logging.critical('critical is no longer logged!')

print(log_stream.getvalue())