A tuple is similar to list but can not be modified
tuple1 = (1,)
tuple2 = (1,2,3,4)
to refer elemetn in a tuple
var1 = tuple[0]
var2 = tuple[-1]
just like what we do to list.
so here is the question, in what condition do we have to use tuple instead of list?
原文：http://www.cnblogs.com/lmliu/p/5560383.html