python logging module is not writing anything to file

Question

I’m trying to write a server that logs exceptions both to the console and to a file. I pulled some code off the cookbook. Here it is:

logger = logging.getLogger('server_logger')
logger.setLevel(logging.DEBUG)
# create file handler which logs even debug messages
fh = logging.FileHandler('server.log')
fh.setLevel(logging.DEBUG)
# create console handler with a higher log level
ch = logging.StreamHandler()
ch.setLevel(logging.ERROR)
# create formatter and add it to the handlers
formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(message)s', datefmt='%Y-%m-%d %H:%M:%S')
ch.setFormatter(formatter)
fh.setFormatter(formatter)
# add the handlers to logger
logger.addHandler(ch)
logger.addHandler(fh)

This code logs perfectly fine to the console, but nothing is logged to the file. The file is created, but nothing is ever written to it. I’ve tried closing the handler, but that doesn’t do anything. Neither does flushing it. I searched the Internet, but apparently I’m the only one with this problem. Does anybody have any idea what the problem is? Thanks for your answers.

Asked By: thePurpleMonkey

||

Source

Answer 1

Try calling

logger.error('This should go to both console and file')

instead of

logging.error('this will go to the default logger which you have not changed the config of')

Answered By: Leopd

Answer 2

I know that this question might be a bit too old but I found the above method a bit of an overkill. I ran into a similar issue, I was able to solve it by:

import logging

logging.basicConfig(format = '%(asctime)s %(message)s',
                    datefmt = '%m/%d/%Y %I:%M:%S %p',
                    filename = 'example.log',
                    level=logging.DEBUG)

This will write to example.log all logs that are of level debug or higher.

logging.debug("This is a debug message") will write This is a debug message to example.log. Level is important for this to work.

Answered By: Abass Sesay

Answer 3

Try to put the import and the basicConfig at the very beggining of the script. Something like this:

import logging
logging.basicConfig(filename='log.log', level=logging.INFO)
.
.
import ...
import ...

Answered By: Fernando Benito

Answer 4

Put this

for handler in logging.root.handlers[:]:
    logging.root.removeHandler(handler)

in front of the

logging.basicConfig(...)

see also
Logging module not writing to file

Answered By: P Moran

Answer 5

In order to both write to terminal and file you can do like below:

import logging.config

logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s [%(levelname)s] %(message)s",
    handlers=[
        logging.FileHandler("log_file.log"),
        logging.StreamHandler()
    ]
)
logger = logging.getLogger(__name__)

usage in the code:

logger.info('message')
logger.error('message')

Answered By: Amirkhm

Answer 6

If root.handlers is not empty, log file will not be created. We should empty root.handlers before calling basicConfig() method. source

Snippet:

for handler in logging.root.handlers[:]:
logging.root.removeHandler(handler)

The full code is below:

import logging
##loging
for handler in logging.root.handlers[:]:
    logging.root.removeHandler(handler)

logging.basicConfig(level=logging.DEBUG,
                    format='%(asctime)s %(message)s',
                    datefmt='%a, %d %b %Y %H:%M:%S',
                    filename= 'log.txt',
                    filemode='w')

console = logging.StreamHandler()
console.setLevel(logging.INFO)
# add the handler to the root logger
logging.getLogger().addHandler(console)
logging.info("nParameters:")

for i in range(10):
    logging.info(i)

logging.info("end!")

Answered By: Umair Qadir

python logging module is not writing anything to file

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