[Tutor] python logging module: two handlers writing to the same file - okay?

[Hans Fangohr]

Dear all,

I am trying to set up a logging system with the following specs:

- all messages should be printed to stdout and to a file (here called log.log).

- we have two types of loggers that the code uses: 'normal' and 'short'.

- The 'short' logger just prints less detail (it
   basically needs another 'formatter'; the code shown here is just a
   simplified version of the actual problem.)

- the formatters appear to be attached to handlers in the logging
   module (if I interpret the module correctly)

- the loggers have handlers, of which we have four:

   - file (for the 'normal' logger to 'log.log')
   - file-short (for the 'short' logger to 'log.log')
   - console (for the 'normal' logger to stdout)
   - console-short (for the 'short' logger to stdout)

I have an example program (test.py) and the logging configuration file
(log.conf) attached below (they are also available at
http://www.soton.ac.uk/~fangohr/geheim/two_handlers_one_file)

Here are the questions:

(i) is this (as in the log.conf file) the right use of the logging
module to achieve what I need?

(ii) in particular, it appears we have two filehandlers that write to
the same file (in mode 'a+'). While this seems to work fine in the
examples I have tested, I'd like some independent advice on whether
this is 'legal' (or whether it works by chance).

(I have seen this not working when both files are opened with mode
'w'.)

Many thanks for your time, and any advice.

Best wishes,

Hans

Files:
---------------
test.py:
---------------

import logging.config
logging.config.fileConfig('log.conf')

normal_log = logging.getLogger('normal')
short_log = logging.getLogger('short')


normal_log.info("A message to file and console")
short_log.info("A short message to file and console")

-----------------
log.conf:
----------------

[loggers]
keys=root,normal,short

[handlers]
keys=console,file,file-short,console-short

[formatters]
keys=consolef,filef,shortf

[logger_root]
level=INFO
handlers=console,file

[logger_normal]
level=NOTSET
handlers=console,file
qualname=normal
propagate=0

[logger_short]
level=NOTSET
handlers=file-short,console-short
qualname=short
propagate=0

[handler_console]
class=StreamHandler
level=NOTSET
formatter=consolef
args=(sys.stdout,)

[handler_file]
class=FileHandler
level=NOTSET
formatter=filef
args=('log.log', 'a+')

[handler_console-short]
class=StreamHandler
level=NOTSET
formatter=shortf
args=(sys.stdout,)

[handler_file-short]
class=FileHandler
level=NOTSET
formatter=shortf
args=('log.log','a+')

[formatter_consolef]
format=%(name)11s:%(asctime)s %(levelname)7s %(message)s
datefmt=

[formatter_filef]
format=%(name)11s:%(asctime)s %(levelname)7s %(message)s
datefmt=

[formatter_shortf]
format=%(name)11s:%(levelname)7s %(message)s 
datefmt=