python logger logging same entry numerous times

Question

I have a such logger initializing function:

def generate_logger():
    import logging
    LOG_FILENAME = os.path.join(PROJECT_DIR, "mylog.log")
    FORMAT = "%(asctime)s : %(message)s"
    logger = logging.getLogger()
    logger.setLevel(logging.INFO)
    fh = logging.FileHandler(LOG_FILENAME)
    formatter = logging.Formatter(FORMAT)
    fh.setFormatter(formatter)
    logger.addHandler(fh)
    return logger

And at some part of my code I have such exception catching:

logger = generate_logger()
except AttributeError:
    logger.error('Opps we got an error')

Weirdly I get same error written 2 times and it can be caugh only once, once I change logger.error('Opps we got an error') with print "test", I get "test" printed once.

What can be the problem and the solution.

Regards

Answer 1

You are adding a new FileHandler to the root logger every time you call that function: the call to logger.getLogger() without a name argument returns the same logger object every time.

You should call generate_logger() only once and then simply get the same logger object by calling logger.getLogger():

generate_logger()

# .... some time later

log = logger.getLogger()
except AttributeError:
   log.error('Opps we got an error')

(note that you do not need generate_logger() to return a value now)

Answer 2

I also faced the same problem and came across this page. Yes, I was also creating multiple handlers. In generate_logger(), you can check if there's any other handlers and delete them.

def generate_logger():
    import logging
    LOG_FILENAME = os.path.join(PROJECT_DIR, "mylog.log")
    FORMAT = "%(asctime)s : %(message)s"
    logger = logging.getLogger()
    logger.setLevel(logging.INFO)
    # Reset the logger.handlers if it already exists.
    if logger.handlers:
        logger.handlers = []
    fh = logging.FileHandler(LOG_FILENAME)
    formatter = logging.Formatter(FORMAT)
    fh.setFormatter(formatter)
    logger.addHandler(fh)
    return logger