collections.Counter：most_common 包括相等计数

In collections.Counter， 方法most_common(n)仅返回列表中 n 个最频繁出现的项目。我正是需要这个，但我也需要包括相等的计数。

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)

我会需要[('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，可能非常大。我需要它有点效率。

你可以这样做：

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)]