Question

我有一个项目列表：

mylist = ['A','A','B','C','D','E','D']

我想返回一个在mylist中出现多次的唯一项目列表，以便我所需的输出为：

 [A,D]

不确定如何成为这个，但我的过程是首先追加每个项目的计数，然后删除等于1的任何内容。然后重复数据删除，但这似乎是一个非常迂回，低效的方法，所以我正在寻求建议。

Answer 1

您可以使用collections.Counter轻松完成您所描述的内容：

from collections import Counter
mylist = ['A','A','B','C','D','E','D']
cnt = Counter(mylist)
print [k for k, v in cnt.iteritems() if v > 1]
# ['A', 'D']

Answer 2

>>> mylist = ['A','A','B','C','D','E','D']
>>> set([i for i in mylist if mylist.count(i)>1])
set(['A', 'D'])

Answer 3

import collections
cc = collections.Counter(mylist) # Counter({'A': 2, 'D': 2, 'C': 1, 'B': 1, 'E': 1})
cc.subtract(cc.keys())           # Counter({'A': 1, 'D': 1, 'C': 0, 'B': 0, 'E': 0})
cc += collections.Counter()      # remove zeros (trick from the docs)
print cc.keys()                  # ['A', 'D']

Answer 4

尝试这样的事情：

a = ['A','A','B','C','D','E','D']

import collections
print [x for x, y in collections.Counter(a).items() if y > 1]
 ['A', 'D']

参考：How to find duplicate elements in array using for loop in Python?

或

def list_has_duplicate_items( mylist ): return len(mylist) > len(set(mylist)) def get_duplicate_items( mylist ): return [item for item in set(mylist) if mylist.count(item) > 1] mylist = [ 'oranges' , 'apples' , 'oranges' , 'grapes' ] print 'List: ' , mylist print 'Does list have duplicate item(s)? ' , list_has_duplicate_items( mylist ) print 'Redundant item(s) in list: ' , get_duplicate_items( mylist )

参考https://www.daniweb.com/software-development/python/threads/286996/get-redundant-items-in-list

Answer 5

在这里使用与其他人相似的方法，继承我的尝试：

from collections import Counter

    def return_more_then_one(myList):
         counts = Counter(my_list)
         out_list = [i for i in counts if counts[i]>1]
         return out_list

Answer 6

它可以像......一样简单。

print(list(set([i for i in mylist if mylist.count(i) > 1])))

Answer 7

可能不如内部实现快，但需要（几乎）线性时间（因为set查找是对数的）

mylist = ['A','A','B','C','D','E','D']
myset = set()
dups = set()
for x in mylist:
    if x in myset:
        dups.add(x)
    else:
        myset.add(x)
dups = list(dups)
print dups

Answer 8

另一种解决方案是什么：

def delete_rep(list_):
new_list = []
for i in list_:
    if i not in list_[i:]:
        new_list.append(i)

return new_list

获取列表中多次出现的项目的唯一列表

8 个答案: