class A():
__init__(self, **arg):
self.__dict__.update(arg)
def M(self, config=None, section=None):
if config is None:
config = self.config
if section is None:
section = self.section
来源：https://www.zhihu.com/question/22959976/answer/23246445
python 类方法中参数使用默认值的方法
原文：http://www.cnblogs.com/white-small/p/6349605.html
