Advantages of logging vs. print() + logging best practices

Question

I'm currently working on 1.0.0 release of pyftpdlib module. This new release will introduce some backward incompatible changes in that certain APIs will no longer accept bytes but unicode. While I'm at it, as part of this breackage, I was contemplating the possibility to get rid of my logging functions, which currently use the print statement, and use the logging module instead.

As of right now pyftpdlib delegates the logging to 3 functions:

def log(s):
   """Log messages intended for the end user."""
   print s

def logline(s):
   """Log commands and responses passing through the command channel."""
   print s

def logerror(s):
   """Log traceback outputs occurring in case of errors."""
   print >> sys.stderr, s

The user willing to customize logs (e.g. write them to a file) is supposed to just overwrite these 3 functions as in:

>>> from pyftpdlib import ftpserver
>>>
>>> def log2file(s):
...        open('ftpd.log', 'a').write(s)
...
>>> ftpserver.log = ftpserver.logline = ftpserver.logerror = log2file

Now I'm wondering: what benefits would imply to get rid of this approach and use logging module instead? From a module vendor perspective, how exactly am I supposed to expose logging functionalities in my module? Am I supposed to do this:

import logging
logger = logging.getLogger("pyftpdlib")

...and state in my doc that "logger" is the object which is supposed to be used in case the user wants to customize how logs behave? Is it legitimate to deliberately set a pre-defined format output as in:

FORMAT = '[%(asctime)] %(message)s'
logging.basicConfig(format=FORMAT)
logger = logging.getLogger('pyftpdlib')

...?

Can you think of a third-party module I can take cues from where the logging functionality is exposed and consolidated as part of the public API?

Thanks in advance.

Answer 1

libraries (ftp server or client library) should never initialize the logging system. So it's ok to instantiate a logger object and to point at logging.basicConfig in the documentation (or provide a function along the lines of basicConfig with fancier output and let the user choose among his logging configuration strategy, plain basicConfig or library provided configuration)

frameworks (e.g. django) or servers (ftp server daemon) should initialize the logging system to a reasonable default and allow for customization of logging system configuration.