n = 7
# case 1
virus_com = [[0]*n]*n
virus_com[1][2] =2
print('virus_com', virus_com)

>>>
virus_com [[0, 0, 2, 0, 0, 0, 0], [0, 0, 2, 0, 0, 0, 0], [0, 0, 2, 0, 0, 0, 0], [0, 0, 2, 0, 0, 0, 0], [0, 0, 2, 0, 0, 0, 0], [0, 0, 2, 0, 0, 0, 0], [0, 0, 2, 0, 0, 0, 0]]

# case 2
virus_com2 = [[0]*n for _ in range(n)]
virus_com2[1][2] =2
print('virus_com2', virus_com2)

>>>
virus_com2 [[0, 0, 0, 0, 0, 0, 0], [0, 0, 2, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0]]

#### case 1 의 경우 곱했더니 아래 숫자도 바뀜