python dict.fromkeys()研究

def unique(seq):
        #return [x for x in my_list if x not in locals()['_[1]']]
        return {}.fromkeys(seq).keys()

dict.fromkeys(seq,val=None) #创建并返回一个新字典，以序列seq中元素做字典的键，val为字典所有键对应的初始值(默认为None)

例子：

1，
>>> l = [1,2,3]
>>> a3 = {}.fromkeys(l)
>>> print a3
{1: None, 2: None, 3: None}
>>> len(a3)
3

2，>>> d = {}.fromkeys(l).keys()
>>> print d
[1, 2, 3]
>>> len(d)
3

还可对list和string去重