How to use Module Logging

Modules in this package (should) provide a thin layer to the python logging module. The idea is to emit messages inside the library and let the user of said library decide on whether they want to see it.

Module setup

Any module interested in logging should include the following header:

import logging
logger=logging.getLogger(__name__)
logger.addHandler(logging.NullHandler())

Inside the module being watch, statements of the kind:

logger.debug('Variable x={0}'.format(x))
logger.warning('File not found, using random data instead. Good luck')

will lead to debug messages. With the default setting the first will be swallowed (since it is not severe enough, i.e. low enough log level), while the second should be visible.

Configuration by the Module User

The importer of the module (e.g. BRUKERIO) needs to issue the following statement in addition to the actual import statement:

#make the SARlogger features available
from sarpy import SARlogger
#test logging for BRUKERIO
import BRUKERIO
SARlogger.initiate_logging(BRUKERIO)

At this point, a console handler that issues anything that’s a WARNING or more sever will be written to to the console. Without the call to sarpy.io.SARlogger.initiate_logging(), logging messages will be ignored alltogether.

If you desire output to a file, another convenience function in SARlogger can be used to attach another handler (with another log level and formatter):

SARlogger.add_file_handler(BRUKERIO)

By default, this will lead to logging at the DEBUG level to file /tmp/SARlabpy.log.

Log levels

Log levels can be changed both at the logger level and the handler level. Note that no log messages are handed on to the handlers if they are above the logger log level. Each individual handler in turn decides whether to publish a received log message or not. This way it is possible to reduce console output to the more severe messages and log every little fart in a log file.

More sophisticated log control

Since the module will expose access to the logger through module attribute logger, logging is as configurable as the python logging module itself. You can attach further handlers, change the levels, come up with new formatters and filters as you desire….