logging module in python 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 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 3: 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")

Example 4: 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())