Python 去除列表中重复的元素

来自比较容易记忆的是用内置的set

l1 = ['b','c','d','b','c','a','a']
l2 = list(set(l1))
print l2

还有一种听说速度更快的，没测试过二者的速度差异

l1 = ['b','c','d','b','c','a','a']
l2 = {}.fromkeys(l1).keys()
print l2

这两种都有个缺点，祛除重复元素后排序变了：

['a', 'c', 'b', 'd']

若是想要保持他们原来的排序：

用list类的sort方法

l1 = ['b','c','d','b','c','a','a']
l2 = list(set(l1))
l2.sort(key=l1.index)
print l2

也能够这样写

l1 = ['b','c','d','b','c','a','a']
l2 = sorted(set(l1),key=l1.index)
print l2

也能够用遍历

l1 = ['b','c','d','b','c','a','a']
l2 = []
for i in l1:
if not i in l2:
        l2.append(i)
print l2

上面的代码也能够这样写

l1 = ['b','c','d','b','c','a','a']
l2 = []
[l2.append(i) for i in l1 if not i in l2]
print l2

这样就能够保证排序不变了：

['b', 'c', 'd', 'a']