获取在列表中出现多次的唯一项目列表 [英] Get a unique list of items that occur more than once in a list

问题描述

我有一个项目清单:

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

我想返回一个在 mylist 中多次出现的项目的唯一列表，以便我想要的输出是:

I want to return a unique list of items that appear more than once in mylist, so that my desired output would be:

 [A,D]

不确定如何做到这一点，但我的流程是首先附加每个项目的计数，然后删除等于 1 的任何内容.然后进行重复数据删除，但这似乎是一种非常迂回、低效的方法，所以我正在寻求建议.

Not sure how to even being this, but my though process is to first append a count of each item, then remove anything equal to 1. Then dedupe, but this seems like a really roundabout, inefficient way to do it, so I am looking for advice.

推荐答案

您可以使用 collections.Counter 可以轻松完成您所描述的操作:

You can use collections.Counter to do what you have described easily:

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']

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