1. Fastest way to check if a value exist in a list
http://stackoverflow.com/questions/7571635/fastest-way-to-check-if-a-value-exist-in-a-list
7 in a
True: 7在list a中；False: 7不在list a中。
Python.list
原文：http://www.cnblogs.com/cwgk/p/4302094.html
