logging模块功能比较多，但一般情况下使用其简单功能就已经足够了。
最简单的用法如下：
import logging
logging.baiscConfig(level=logging.DEBUG)
logging.debug('message')
logging.critical('message')
logging.warning('%s before you %s', 'Look', 'leap!')
logging.warning('{} before you {}'.format('Look', 'leap!'))
如果对日志格式、输出、日期格式等有要求，可以增加basicConfig的关键字参数，如：
logging.basicConfig(filename='example.log',level=logging.DEBUG)
对于basicConfig方法所有的关键字参数如下：
logging.basicConfig(**kwargs)
Does basic configuration for the logging system by creating a StreamHandler with a default Formatter and adding it to the root logger. The functions debug(), info(), warning(), error() and critical() will call basicConfig() automatically if no handlers are defined for the root logger.
