[Python] Collections 모듈: counter, most_common

counter 함수

collections.Counter(iterable): return dict

예제코드

import collections 

a = [1,2,3,4,1,1,2,3,4]
b = [1,2,3,4,1,1,5,6,7]
print(collections.Counter(a),'\n', collections.Counter(b))
print(type(collections.Counter(a)))

결과

>>>
Counter({1: 3, 2: 2, 3: 2, 4: 2}) 
Counter({1: 3, 2: 1, 3: 1, 4: 1, 5: 1, 6: 1, 7: 1})
<class 'collections.Counter'>

counter 연산

+, -, &(교집합), |(교집합) 연산 가능

예제코드

import collections

a = [1,2,3,4,1,1,2,3,4]
b = [1,2,3,4,1,1,5,6,7]
print(collections.Counter(a))
print(collections.Counter(b))
print(collections.Counter(a) + collections.Counter(b))
print(collections.Counter(a) - collections.Counter(b))
print(collections.Counter(a) & collections.Counter(b))
print(collections.Counter(a) | collections.Counter(b))

결과

>>>
Counter({1: 3, 2: 2, 3: 2, 4: 2})
Counter({1: 3, 2: 1, 3: 1, 4: 1, 5: 1, 6: 1, 7: 1})
Counter({1: 6, 2: 3, 3: 3, 4: 3, 5: 1, 6: 1, 7: 1})
Counter({2: 1, 3: 1, 4: 1})
Counter({1: 3, 2: 1, 3: 1, 4: 1})
Counter({1: 3, 2: 2, 3: 2, 4: 2, 5: 1, 6: 1, 7: 1})

most_common() 함수: 최빈값

collections.Counter(a).most_common(n): return list(tuple)

예제코드

import collections
a  = [1,1,1,2,3,2,3,10,9]

print(collections.Counter(a).most_common(3))

결과

>>>
[(1, 3), (2, 2), (3, 2)]