如何在Python中从列表中获取最常见的元素

Question

我有一个如下所示的列表。a=[1936,2401,2916,4761,9216,9216,9604,9801] 我想要获取具有更多重复项的值。在这里是 '9216'，我该如何获取这个值？谢谢

- Dimuth Ruwantha

Answer 1

你可以使用collections.Counter来完成这个任务：

from collections import Counter

a = [1936, 2401, 2916, 4761, 9216, 9216, 9604, 9801] 

c = Counter(a)

print(c.most_common(1)) # the one most common element... 2 would mean the 2 most common
[(9216, 2)] # a set containing the element, and it's count in 'a'

来自文档：

- Totem

Answer 2

这有两种标准库方法可以实现： statistics.mode： 请参见文档。

from statistics import mode
most_common = mode([3, 2, 2, 2, 1])  # 2
most_common = mode([3, 2])  # StatisticsError: no unique mode

collections.Counter.most_common:

from collections import Counter
most_common, count = Counter([3, 2, 2, 2, 1]).most_common(1)[0]  # 2, 3
most_common, count = Counter([3, 2]).most_common(1)[0]  # 3, 1

两者在性能方面完全相同，但第一个会在没有唯一最常见元素时引发异常，而第二个也会返回频率。

- Matthew D. Scholefield

Answer 3

这是另一个不使用计数器的例子。

a=[1936,2401,2916,4761,9216,9216,9604,9801]
frequency = {}
for element in a:
    frequency[element] = frequency.get(element, 0) + 1
# create a list of keys and sort the list
# all words are lower case already
keyList = frequency.keys()
keyList.sort()
print "Frequency of each word in the word list (sorted):"
for keyElement in keyList:
    print "%-10s %d" % (keyElement, frequency[keyElement])

- Stefan Gruenwald

Answer 4

https://docs.python.org/2.7/library/collections.html#counter

从 collections 模块导入 Counter Counter(a).most_common(1)

- gyu-don