Python 去除列表中重复的元素

python

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

 

还有一种据说速度更快的,没测试过两者的速度差别

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']

 

  

  

如果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

也可以这样写

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

 

 

也可以用遍历

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

上面的代码也可以这样写

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

 

 

这样就可以保证排序不变了:

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

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