Python using basicConfig method to log to console

Question

I don't know why this code prints to the screen, but not to the file? File "example1.log" is created, but nothing is written there.

#!/usr/bin/env python3
import logging

logging.basicConfig(level=logging.DEBUG,
                    format='%(asctime)s %(message)s',
                    handlers=[logging.FileHandler("example1.log"),
                              logging.StreamHandler()])
logging.debug('This message should go to the log file and to the console')
logging.info('So should this')
logging.warning('And this, too')

I have "bypassed" this problem by creating a logging object (example code), but it keeps bugging me why basicConfig() approach failed?

PS. If I change basicConfig call to:

logging.basicConfig(level=logging.DEBUG,
                    filename="example2.log",
                    format='%(asctime)s %(message)s',
                    handlers=[logging.StreamHandler()])

Then all logs are in the file and nothing is displayed in the console

Answer 1

In the example below, you can specify the log destination based on its level. For example, the code below lets all logs over the INFO level go to the log file, and all above ERROR level goes to the console.

import logging
logging.root.handlers = []
logging.basicConfig(format='%(asctime)s : %(levelname)s : %(message)s', level=logging.INFO , filename='ex.log')

# set up logging to console
console = logging.StreamHandler()
console.setLevel(logging.ERROR)
# set a format which is simpler for console use
formatter = logging.Formatter('%(asctime)s : %(levelname)s : %(message)s')
console.setFormatter(formatter)
logging.getLogger("").addHandler(console)

logging.debug('debug')
logging.info('info')
logging.warning('warning')
logging.error('error')
logging.exception('exp')

Answer 2

Reusable logger function.

def logger(logPath,fileName):
    logging.basicConfig(
        format='%(asctime)s - %(levelname)s - %(message)s',
        level=logging.INFO,
        handlers=[
            logging.FileHandler("{0}/{1}.log".format(logPath,fileName)),
            logging.StreamHandler()
        ])
    return logging

On Other python file, import the logger

logger().info("this is info")
logger().critical('404')
logger().error("this is error")

Answer 3

I can't reproduce it on Python 3.3. The messages are written both to the screen and the 'example2.log'. On Python <3.3 it creates the file but it is empty.

The code:

from logging_tree import printout  # pip install logging_tree
printout()

shows that FileHandler() is not attached to the root logger on Python <3.3.

The docs for logging.basicConfig() say that handlers argument is added in Python 3.3. The handlers argument isn't mentioned in Python 3.2 documentation.

Answer 4

Try this working fine(tested in python 2.7) for both console and file

# set up logging to file
logging.basicConfig(
     filename='twitter_effect.log',
     level=logging.INFO, 
     format= '[%(asctime)s] {%(pathname)s:%(lineno)d} %(levelname)s - %(message)s',
     datefmt='%H:%M:%S'
 )

# set up logging to console
console = logging.StreamHandler()
console.setLevel(logging.DEBUG)
# set a format which is simpler for console use
formatter = logging.Formatter('%(name)-12s: %(levelname)-8s %(message)s')
console.setFormatter(formatter)
# add the handler to the root logger
logging.getLogger('').addHandler(console)

logger = logging.getLogger(__name__)