python日志记录：记录器不会写入文件

Question

Im working on a project with several modules that should all log to the same file.

Initializing the logger:

parentLogger = logging.getLogger('PARENTLOGGER')
logger = logging.getLogger('PARENTLOGGER.' + __name__)
#set format
fmt = logging.Formatter('%(asctime)s [%(levelname)s] %(name)s: %(message)s')
#set handler for command line
ch = logging.StreamHandler()
ch.setLevel(logging.DEBUG)
ch.setFormatter(fmt)
#set file handler
open('data/logs.log', 'w+').close() #for creating the file in case it doesnt exists. I got exceptions otherwise.
fh = RotatingFileHandler('data/logs.log', maxBytes=5242880, backupCount=1)
fh.setLevel(logging.DEBUG)
fh.setFormatter(fmt)
parentLogger.addHandler(fh)
parentLogger.addHandler(ch)
#

than, on all other modules im calling:

self._logger = logging.getLogger('PARENTLOGGER.' + __name__)

The problem is that the rotating file handler wont write anything to the log file. In any module.

Am I configuring the logger correctly? I've tried several examples from pythons' logging cookbook without success...

Regards and thanks in advance!

Answer 1

You should tell logging when and what to log. Also, the log file will be created by default, no need to create it yourself. Here's a simple example:

$ cat test_log.py
import logging

log = '/home/user/test_log.log'
logging.basicConfig(filename=log,
                    format='%(asctime)s [%(levelname)s]: %(message)s at line: %(lineno)d (func: "%(funcName)s")')

try:
    this_will_fail
except Exception as err:
    logging.error('%s' % err)
$ python test_log.py
$ cat /home/user/test_log.log
2018-02-07 11:31:24,127 [ERROR]: name 'this_will_fail' is not defined at line: 10 (func: "<module>")