Python - permutations 클래스 함수

 

퍼뮤테이션(permutation): 순열 또는 치환

permutations(n, r).
입력된 n개를 이용하여 조합이 반복되지 않게(서로 다른 순서로 반복은 가능) r개씩 짝을 지어 반환. 반환되는 방식은 iterable이다. 조합에 순서를 구분하여 다른 순서는 다른 조합으로 인식.

>>> import itertools
>>> list(itertools.permutations([11,22,33,44],1))
[(11,), (22,), (33,), (44,)]
>>> list(itertools.permutations([11,22,33,44],2))
[(11, 22), (11, 33), (11, 44), (22, 11), (22, 33), (22, 44), (33, 11), (33, 22),
 (33, 44), (44, 11), (44, 22), (44, 33)]
>>> list(itertools.permutations([11,22,33,44],3))
[(11, 22, 33), (11, 22, 44), (11, 33, 22), (11, 33, 44), (11, 44, 22), (11, 44,
33), (22, 11, 33), (22, 11, 44), (22, 33, 11), (22, 33, 44), (22, 44, 11), (22,
44, 33), (33, 11, 22), (33, 11, 44), (33, 22, 11), (33, 22, 44), (33, 44, 11), (
33, 44, 22), (44, 11, 22), (44, 11, 33), (44, 22, 11), (44, 22, 33), (44, 33, 11
), (44, 33, 22)]
>>> list(itertools.permutations([11,22,33,44],4))
[(11, 22, 33, 44), (11, 22, 44, 33), (11, 33, 22, 44), (11, 33, 44, 22), (11, 44
, 22, 33), (11, 44, 33, 22), (22, 11, 33, 44), (22, 11, 44, 33), (22, 33, 11, 44
), (22, 33, 44, 11), (22, 44, 11, 33), (22, 44, 33, 11), (33, 11, 22, 44), (33,
11, 44, 22), (33, 22, 11, 44), (33, 22, 44, 11), (33, 44, 11, 22), (33, 44, 22,
11), (44, 11, 22, 33), (44, 11, 33, 22), (44, 22, 11, 33), (44, 22, 33, 11), (44
, 33, 11, 22), (44, 33, 22, 11)]
>>> list(itertools.permutations([11,22,33,44],5))
[]
>>>

순서가 다른 같은 값 조합을 피하려면 combination함수 참고: 2020/09/06 - Python - combination 클래스 함수