Excellent point:
http://inventwithpython.com/blog/2012/04/06/stop-using-print-for-debugging-a-5-minute-quickstart-guide-to-pythons-logging-module/

import logging

logging.basicConfig(level=logging.DEBUG, 
    format='%(asctime)s - %(levelname)s - %(message)s')

logging.debug('message')

In Ruby:

http://www.ruby-doc.org/stdlib-1.9.3/libdoc/logger/rdoc/Logger.html

require 'logger'

log = Logger.new(STDOUT)
log.level = Logger::WARN

log.debug("Created logger")
log.info("Program started")
log.warn("Nothing to do!")