Using a variable while calling logger.setLevel

Question

Does anyone know if there is a way to use a variable in the setlevel() function of Python's Logging module?

At the moment I am using this:

Log = logging.getLogger('myLogger')
Log.setLevel(logging.DEBUG)

But I'd like to have this:

Log = logging.getLogger('myLogger')
levels = {'CRITICAL' : logging.critical,
    'ERROR' : logging.error,
    'WARNING' : logging.warning,
    'INFO' : logging.info,
    'DEBUG' : logging.debug
}
level = levels['INFO']
Log.setLevel(level)

But it doesn't seem to work - it just doesn't log anything.

I'm doing this so that I can set the logging level for a whole bunch of scripts from a variable in a single config file.

Shutout

You should use uppercase in your dict values: ERROR: logging.ERROR etc – Perilous

Also, Have a look at the logging documentation on this: docs.python.org/howto/logging.html#logging-levels. Logging levels are just numeric values. – Upchurch

Answer 1

You should also be able to do this:

Log = logging.getLogger('myLogger')
level = logging.getLevelName('INFO')
Log.setLevel(level)

The logging.getLevelName(lvl) function works both ways. I use it, it works (you should check your python implementation though).

This saves you the trouble to maintain your own dictionary, and reduces the possibility of typo errors.

Roshelle

quote: "In Python versions earlier than 3.4, this function could also be passed a text level, and would return the corresponding numeric value of the level. This undocumented behaviour was considered a mistake, and was removed in Python 3.4, but reinstated in 3.4.2 due to retain backward compatibility." – Catalpa

Answer 2

logging.setLevel() takes an int or a str.

So the following works just fine (at least in Python 3.7):

logger = logging.getLogger(__name__)
logger.setLevel("DEBUG")

Stamper

According to the documentation this works since Python 3.2: Changed in version 3.2: The level parameter now accepts a string representation of the level such as ‘INFO’ as an alternative to the integer constants such as INFO. Note, however, that levels are internally stored as integers, and methods such as e.g. getEffectiveLevel() and isEnabledFor() will return/expect to be passed integers. Source: docs.python.org/3/library/logging.html#logging.Logger.setLevel – Charmian

Answer 3

I had problems with python 3 and got this working for me: https://docs.python.org/3/howto/logging.html

# myapp.py
import logging
import mylib

def main():
    logging.basicConfig(filename='myapp.log', level=logging.INFO)
    logging.info('Started')
    mylib.do_something()
    logging.info('Finished')

if __name__ == '__main__':
    main()

Chowchow

+1 I like the way you have all the logging calls within a function definition. This reduces the likelyhood of import lock problems with logging. – Luminescence

Answer 4

What about using getattr on logging module?

import logging
str_level = 'DEBUG'
level = getattr(logging, str_level)
logger = logging.getLogger("my_logger")
logger.setLevel(level)
print(logger.getEffectiveLevel())

Religieux

Answer 5

I find that leveraging an optional environmental variable is very convenient and flexible:

class Foo():
    def __init__(self):
        self.logger = logging.getLogger(__name__)
        level = logging.getLevelName(os.environ.get('LOG_LEVEL', 'ERROR'))
        logging.basicConfig(level=level)

    def bar(self):
        self.logger.debug('Log something')

Outgoings

Answer 6

I was able to get this working below. I added a environment variable section as I am using this in a Docker but you can add it in as you see fit. This way you can select what you need and re-run your script.

#Manual Testing Variables If Needed
#os.environ["LOG_LEVEL_SELECTOR"] = "DEBUG, INFO, or ERROR"

#Setting Log Level Test
logger = logging.getLogger('json')
logger.addHandler(json_handler_out)
logger_levels = {
    'ERROR' : logging.ERROR,
    'INFO' : logging.INFO,
    'DEBUG' : logging.DEBUG
}
logger_level_selector = os.environ["LOG_LEVEL_SELECTOR"]
logger.setLevel(logger_level_selector)

Libation