Python has a nice logging module. You can use it like this:
Stream output
#!/usr/bin/env python
import logging
import sys
logging.basicConfig(format='%(asctime)s %(levelname)s %(message)s',
level=logging.DEBUG,
stream=sys.stdout)
logging.debug('This message should go to the log file')
logging.info('So should this')
logging.warning('And this, too')
File output
#!/usr/bin/env python
import logging
logging.basicConfig(filename='logging.log',
format='%(asctime)s %(levelname)s %(message)s',
level=logging.DEBUG)
logging.debug('This message should go to the log file')
logging.info('So should this')
logging.warning('And this, too')