python 判空常用 XX is not None,但其实 not XX is None 也可以。
http://stackoverflow.com/questions/2710940/python-if-x-is-not-none-or-if-not-x-is-none
python 判空常用 XX is not None,但其实 not XX is None 也可以。
http://stackoverflow.com/questions/2710940/python-if-x-is-not-none-or-if-not-x-is-none