Different logging levels for filehandler and display in Python

user_774163 0
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I am using the logging module in Python to write debug and error messages.

I want to write to file all messages of logging.DEBUG or greater.

However, I only want to print to the screen messages of logging.WARNING or greater.

Is this possible using just one Logger and one FileHandler?

logging python
4 Answers

You can append lots of handlers to the same logger with different loglevel, but root loglevel must be as verbose as the most verbose handler. This example log messages to file with log.debug() and log.info() to console:

log = logging.getLogger("syslog2elastic")
log.setLevel(logging.DEBUG) # this must be DEBUG to allow debug messages through

console = logging.StreamHandler()
console.setLevel(logging.INFO)
formatter = logging.Formatter("%(asctime)s.%(msecs)03d - %(name)s:%(lineno)d - %(levelname)s - %(message)s", "%Y%m%d%H%M%S")
console.setFormatter(formatter)
log.addHandler(console)

fh = RotatingFileHandler(args.logfile, maxBytes=104857600, backupCount=5)
fh.setLevel(logging.DEBUG)
formatter = logging.Formatter("%(asctime)s.%(msecs)03d - %(message)s", "%Y%m%d%H%M%S")
fh.setFormatter(formatter)
log.addHandler(fh)
user_5362620

You can do this in the following way, making two loggers, one for file logging, another one for console logging. Make sure to set the root logger to the most verbose of the two.

import logging

logging.getLogger().setLevel(logging.DEBUG)  # This must be as verbose as the most verbose handler

formatter = logging.Formatter(
    '%(asctime)s.%(msecs)03d %(levelname)s %(module)s - %(funcName)s [%(lineno)s]: %(message)s',
    datefmt='%Y-%m-%d %H:%M:%S',
)

console_logging = logging.StreamHandler()
console_logging.setLevel(logging.WARNING)
console_logging.setFormatter(formatter)
logging.getLogger().addHandler(console_logging)

file_logging = logging.FileHandler('file.log')
file_logging.setLevel(logging.DEBUG)
file_logging.setFormatter(formatter)
logging.getLogger().addHandler(file_logging)
user_90229660
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