import logging

logging_config = {
    'filename': '/var/log/app_log',
    'format': '%(asctime)s [%(levelname)s] %(message)s',
    'level': logging.INFO
}
logging.basicConfig(**logging_config)

logging.info('Our logged message.')

This will output the following to /var/log/app_log:

2016-11-21 23:50:53,677 [INFO] Our logged message.

Source: https://docs.python.org/2/howto/logging.html#logging-basic-tutorial