總和列

Question

INPUT：

M = [[1,2,3], 
    [1,2,3], 
    [1,2,3]] 

如何採取列的總和的兩個第一行和所述陣列中實施它中號

OUTPUT：

M = [[2,4,6], 
    [1,2,3]] 

Answer 1

使用numpy.add.reduceat：

import numpy as np 
M = [[1,2,3], 
    [1,2,3], 
    [1,2,3]] 

np.add.reduceat(M, [0, 2])  
# indices [0,2] splits the list into [0,1] and [2] to add them separately, 
# you can see help(np.add.reduceat) for more 

# array([[2, 4, 6], 
#  [1, 2, 3]]) 

Answer 2

M = [[1, 2, 3], 
    [4, 5, 6], 
    [7, 8, 9]] 

M[:2] = [[a + b for a, b in zip(M[0], M[1])]] 

print(M) # [[5, 7, 9], [7, 8, 9]] 

個

觀光谷歌明白這一點：

• M[:2] =：蟒蛇片分配
• [... for .. in ...]：Python列表理解
• for a, b in ...：蟒蛇元組拆包環