Python logging - multiple modules

Question

I'm working on a small python project that has the following structure -

project 
 -- logs
 -- project
    __init.py__
    classA.py
    classB.py
    utils.py
 -- main.py

I've set up the logging configuration in __init.py__ under project as follows:

import logging
from logging import StreamHandler
from logging.handlers import RotatingFileHandler

# Create the Logger
logger = logging.getLogger(__name__)
logger.setLevel(logging.INFO)

# Create the Handler for logging data to a file
logger_handler = RotatingFileHandler('logs\\mylog.log', maxBytes=1024, backupCount=5)
logger_handler.setLevel(logging.INFO)

#Create the Handler for logging data to console.
console_handler = StreamHandler()
console_handler.setLevel(logging.INFO)

# Create a Formatter for formatting the log messages
logger_formatter = logging.Formatter('%(name)s - %(levelname)s - %(message)s')

# Add the Formatter to the Handler
logger_handler.setFormatter(logger_formatter)
console_handler.setFormatter(logger_formatter)

# Add the Handler to the Logger
logger.addHandler(logger_handler)
logger.addHandler(console_handler)

Setting up things this way seems to set up the root logger at the package level, and not at the entire project level. As a result, logged statements inside main.py don't appear in the log file, whereas all log statements in the two classes classA and classB as well as utils.py are routed to the console and the log file as expected.

How do I set up the logging so that I'm able to configure it once and use it across the project? I tried moving the logging configuration statements to main.py, but it didn't seem to work.

def setupLogging():
    # Create the Logger
    logger = logging.getLogger(__name__)
    logger.setLevel(logging.INFO)
    ..etc..

def main():   
    setupLogging()

if __name__ == "__main__":
    main()

Answer 1

It is correct to configure logging only once for the whole project, as you first tried, not each package separately.

What you did wrong is you configured the logger for the current module only:

logger = logging.getLogger(__name__)

Instead of that, you want to configure the root logger:

root_logger = logging.getLogger()
root_logger.setLevel(logging.INFO)

# ...

root_logger.addHandler(logger_handler)
root_logger.addHandler(console_handler)

The configuration done for the root logger applies to every logger which does not explicitly override it.

Then you should use the specific logger when actually logging:

logger = logging.getLogger(__name__)

logger.warning("I am warning you about %s", something)