logging_example.py

import logging
import logging_example2

def main():
    # default write changed (in stream, not in file)
    logging.basicConfig(format='%(asctime)s - %(name)s - %(levelname)s : %(message)s',
                        datefmt='%d-%b-%y %H:%M:%S',
                        level=logging.INFO)
    logger = logging.getLogger()  # get the logger with default name 'root'
    
    # in order to write to a file, root.handlers must be empty
    # if log to file does not work, add these 2 lines:
    # Soruce: https://www.tutorialexample.com/fix-python-logging-module-not-writing-to-file-python-tutorial/
    # for handler in logging.root.handlers[:]:
    #    logging.root.removeHandler(handler)

    # add handler to write log to file
    f_handler = logging.FileHandler('file.log', 'w')  # 'w' erase, 'a' append
    f_handler.setLevel(logging.INFO)
    f_format = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')  # format in file!
    f_handler.setFormatter(f_format)
    logger.addHandler(f_handler)
    # end write log to file

    # add a stream without format (in stream, not in file)
    stream_handler = logging.StreamHandler()
    stream_handler.setLevel(logging.DEBUG)
    logger.addHandler(stream_handler)


    logger.info("test to write in file and streams")  # 2 streams: 1 formatted, one not; 1 file: date formatted differently
    
    logging_example2.do_something()  # other logger name


if __name__ == '__main__':
    main()