list comprehension 예

1. 간단 예제
In [1]: m=[[1,2,3],[4,5,6],[7,8,9]]

In [2]: m
Out[2]: [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

In [3]: col2=[row[2] for row in m]

In [4]: col2
Out[4]: [3, 6, 9] 
 
 
2. 리스트 연산
In [6]: m2=[row+[1] for row in m]

In [7]: m2
Out[7]: [[1, 2, 3, 1], [4, 5, 6, 1], [7, 8, 9, 1]]
 
 
3. 각각의 원소에 1씩 더하기
In [9]: m3=[[row[0]+1,row[1]+1,row[2]+1] for row in m]

In [10]: m3
Out[10]: [[2, 3, 4], [5, 6, 7], [8, 9, 10]]
 

4. 튜플 형태로 변환
In [11]: m3=[(row[0]+1,row[1]+1,row[2]+1) for row in m]

In [12]: m3
Out[12]: [(2, 3, 4), (5, 6, 7), (8, 9, 10)]
 
 
5. 리스트 괄호에 유의
In [13]: m3=[[row[i]+1] for row in m for i in [0,1,2]]

In [14]: m3
Out[14]: [[2], [3], [4], [5], [6], [7], [8], [9], [10]]

In [15]: m3=[row[i]+1 for row in m for i in [0,1,2]]

In [16]: m3
Out[16]: [2, 3, 4, 5, 6, 7, 8, 9, 10] 
 
 
6. for-in-if 문
In [24]: l=[row[1] for row in m if row[1] % 2 == 0]

In [25]: l
Out[25]: [2, 8]