This module demonstrates a basic application of the Python Standard Library's logging module by using logging to implement a decorator that logs all calls to a function, method or property.

log_calls.py

#!/usr/bin/python
# -*- coding: utf-8 -*-
##
# log_calls.py: Decorator for logging calls to a function.
##
# © 2013 Christopher E. Granade (cgranade@gmail.com).
#
# Licensed under the AGPL version 3.
##
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
##
"""
This module demonstrates a basic application of the Python Standard Library's
`logging module`_ by using ``logging`` to implement a decorator that logs all
calls to a function, method or property.

.. logging module: http://docs.python.org/2/library/logging.html
"""

## IMPORTS ####################################################################

import functools
import logging

## DECORATORS #################################################################

def log_calls(name=None):
    """
    Causes all calls to the decorated function to be logged.
    """

    def decorator(fn):    
        _name = getattr(fn, '__name__', '<unnamed>') if name is None else name
        logger = logging.getLogger(fn.__module__)
        
        @functools.wraps(fn)
        def logging_fn(*args, **kwargs):
            logger.debug("{name}({args}{comma}{kwargs})".format(
                name=_name,
                args=", ".join(map(repr, args)),
                comma=", " if kwargs else "",
                kwargs=", ".join("{}={}".format(key, val) for key, val in kwargs.iteritems())
            ))
            return fn(*args, **kwargs)
        return logging_fn
    return decorator

## DEMONSTRATION ##############################################################

if __name__ == "__main__":
    logging.basicConfig(level=logging.DEBUG)
    
    class Example(object):
        @log_calls()
        def __init__(self, x):
            self._x = x
            
        @property
        def x(self):
            return self._x
        @x.setter
        @log_calls(name='x.setter')
        def x(self, newval):
            self._x = newval
            
        @log_calls()
        def print_x(self):
            print self.x
   
    ex = Example(3)
    ex.x = 4
    ex.print_x()