collections.Counter:most_common包括相等的计数

问题描述

在collections.Counter中，方法most_common(n)仅返回列表中的n个最频繁的项.我确实需要这个，但是我也需要包括相等的计数.

In collections.Counter, the method most_common(n) returns only the n most frequent items in a list. I need exactly that but I need to include the equal counts as well.

from collections import Counter
test = Counter(["A","A","A","B","B","C","C","D","D","E","F","G","H"])
-->Counter({'A': 3, 'C': 2, 'B': 2, 'D': 2, 'E': 1, 'G': 1, 'F': 1, 'H': 1})
test.most_common(2)
-->[('A', 3), ('C', 2)

我需要[('A', 3), ('B', 2), ('C', 2), ('D', 2)]因为在这种情况下，它们的计数与n = 2相同.我的真实数据是DNA代码，可能很大.我需要它有些效率.

I would need [('A', 3), ('B', 2), ('C', 2), ('D', 2)]since they have the same count as n=2 for this case. My real data is on DNA code and could be quite large. I need it to be somewhat efficient.

推荐答案

您可以执行以下操作:

from itertools import takewhile

def get_items_upto_count(dct, n):
  data = dct.most_common()
  val = data[n-1][1] #get the value of n-1th item
  #Now collect all items whose value is greater than or equal to `val`.
  return list(takewhile(lambda x: x[1] >= val, data))

test = Counter(["A","A","A","B","B","C","C","D","D","E","F","G","H"])

print get_items_upto_count(test, 2)
#[('A', 3), ('C', 2), ('B', 2), ('D', 2)]

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