Do I need to explicitly check for __name__ == "__main__" before calling getLogger in Python?

Question

I believe it's standard practice when using Python's built-in logging module to have the logger in the main module be the root logger. Assuming this is correct, it seems to me that for any module that may or may not be run as main I need to explicitly check. The reason is that if I follow the standard practice of calling logging.getLogger(__name__) I'll get a logger named __main__ rather than the root logger:

import logging
print logging.getLogger().name # root
print logging.getLogger(__name__).name # __main__

Is the best practice always to check?

if __name__ == "__main__":
    logger = logging.getLogger()
else:
    logger = logging.getLogger(__name__)

This is not so bad because I'll always have other code that only runs if __name__ == "__main__" (often including a call to logging.basicConfig) but it would be nice to need only one line instead of more.

Answer 1

Yes - i believe that's a good idea. Because - what happens is as follows -

If you are running a program as python prog.py - (the __name__ would be __main__) and you'd get the root logger (expected). Or you can even give a name that you'd like (say prog). and when you import that module - the name would be the name of the module. (python file name without the extension in this case prog), which will help you identify the origin of the logs - which is what you'd want. So in general it'd be a good idea to do so.

Answer 2

The practice of using logging.getLogger(__name__) is meant for a module-level logger, as explained in the advanced logging tutorial.

In a script (or the main module of an application) I generally don't create a logger at all, but I do change the configuration of the root logger;

opts = argparse.ArgumentParser(prog='foo', description=__doc__)
group.add_argument('-v', '--version', action='version',
                   version=__version__)
opts.add_argument('--log', default='warning',
                  choices=['debug', 'info', 'warning', 'error'],
                  help="logging level (defaults to 'warning')")
opts.add_argument("files", metavar='file', nargs='*',
                  help="one or more files to process")
args = opts.parse_args(argv)
logging.basicConfig(level=getattr(logging, args.log.upper(), None),
                    format='%(levelname)s: %(message)s')