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If I create a logger object by using logger = logging.getLogger("Name") I am unable to change the filemode from append('a') to write ('w'). I can if I use the root logger with basicConfig, but then I get a lot of system debug messages being logged when all I want is my own messages beginning at the DEBUG level.
I am hoping to either (1) change the filemode for my own logger object to 'w' or (2) add a filter to the root logger. Is it even possible to filter out these debug messages from the root logger?
def create_log():
# create logger for "Sample App"
logger = logging.getLogger('automated_testing')
logger.setLevel(logging.DEBUG)
# create file handler which logs even debug messages
fh = logging.FileHandler('results.log')
fh.setLevel(logging.DEBUG)
# create console handler with a higher log level
ch = logging.StreamHandler(stream=sys.stdout)
ch.setLevel(logging.DEBUG)
# create formatter and add it to the handlers
formatter = logging.Formatter('[%(asctime)s] %(levelname)8s --- %(message)s ' +
'(%(filename)s:%(lineno)s)',datefmt='%Y-%m-%d %H:%M:%S')
fh.setFormatter(formatter)
ch.setFormatter(formatter)
# add the handlers to the logger
logger.addHandler(ch)
logger.addHandler(fh)
return logger
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The filemode can be changed to write mode, which will overwrite the previous logs and only save the current ones. Since the filemode is set to w , this means that the log file will be opened in write mode each time basicConfig() is run, which will ultimately overwrite the file.
You can set a different logging level for each logging handler but it seems you will have to set the logger's level to the "lowest". In the example below I set the logger to DEBUG, the stream handler to INFO and the TimedRotatingFileHandler to DEBUG. So the file has DEBUG entries and the stream outputs only INFO.
logger = logging.getLogger(__name__) This means that logger names track the package/module hierarchy, and it's intuitively obvious where events are logged just from the logger name. Sounds like good advice.
The default setting in basicConfig () is to set the logger to write to the console in the following format: While you can pass any variable that can be represented as a string from your program as a message to your logs, there are some basic elements that are already a part of the LogRecord and can be easily added to the output format.
A FileMode parameter is specified in many of the constructors for FileStream, IsolatedStorageFileStream, and in the Open methods of File and FileInfo to control how a file is opened. FileMode parameters control whether a file is overwritten, created, opened, or some combination thereof. Use Open to open an existing file.
The filemode is set to w, which means the log file is opened in “write mode” each time basicConfig () is called, and each run of the program will rewrite the file. The default configuration for filemode is a, which is append. You can customize the root logger even further by using more parameters for basicConfig (), which can be found here.
The default is a, which means append. format: This is the format of the log message. By using the level parameter, you can set what level of log messages you want to record. This can be done by passing one of the constants available in the class, and this would enable all logging calls at or above that level to be logged.
Something like:
import sys
import logging
def create_logger():
# create logger for "Sample App"
logger = logging.getLogger('automated_testing')
logger.setLevel(logging.DEBUG)
# create file handler which logs even debug messages
fh = logging.FileHandler('results.log', mode='w')
fh.setLevel(logging.DEBUG)
# create console handler with a higher log level
ch = logging.StreamHandler(stream=sys.stdout)
ch.setLevel(logging.INFO)
# create formatter and add it to the handlers
formatter = logging.Formatter('[%(asctime)s] %(levelname)8s --- %(message)s ' +
'(%(filename)s:%(lineno)s)',datefmt='%Y-%m-%d %H:%M:%S')
fh.setFormatter(formatter)
ch.setFormatter(formatter)
# add the handlers to the logger
logger.addHandler(ch)
logger.addHandler(fh)
return logger
logger = create_logger()
logger.log(logging.NOTSET, "NOTSET Message - 0")
logger.log(logging.DEBUG, "DEBUG Message - 10")
logger.log(logging.INFO, "INFO Message - 20")
logger.log(logging.WARNING, "WARNING Message - 30")
logger.log(logging.CRITICAL, "CRITICAL Message - 40")
Prints to stdout:
[2015-03-16 17:51:08] INFO --- INFO Message - 20 (temp3.py:34) [2015-03-16 17:51:08] WARNING --- WARNING Message - 30 (temp3.py:35) [2015-03-16 17:51:08] CRITICAL --- CRITICAL Message - 40 (temp3.py:36)
Writes (not appends) to results.log:
[2015-03-16 17:51:08] DEBUG --- DEBUG Message - 10 (temp3.py:33) [2015-03-16 17:51:08] INFO --- INFO Message - 20 (temp3.py:34) [2015-03-16 17:51:08] WARNING --- WARNING Message - 30 (temp3.py:35) [2015-03-16 17:51:08] CRITICAL --- CRITICAL Message - 40 (temp3.py:36)
DEBUG+ are logged in results.txt while only INFO+ are send to stdout.
Note that the NOTSET log entry is passed up to the root logger then, since you don't have any handlers on the root logger, discarded.
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