dante21

import numpy as np
an=np.array([[1,2,3,4],[5,6,7,8],[9,10,11,12]])
bn=np.empty(shape=(an.shape[1],an.shape[0]))
for i in range(an.shape[0]):   
    for j in range(an.shape[1]):      
        bn[j,an.shape[0]-1-i]=an[i,j]

array([[ 1,  2,  3,  4],
       [ 5,  6,  7,  8],
       [ 9, 10, 11, 12]])

array([[ 9.,  5.,  1.],
       [10.,  6.,  2.],
       [11.,  7.,  3.],
       [12.,  8.,  4.]])

n=3
m=4
a=[[1,2,3,4],[5,6,7,8],[9,10,11,12]]
k=[[0,0,0],[0,0,0],[0,0,0],[0,0,0]]
for i in range(n):   
    for j in range(m):    
        k[j][n-1-i]=a[i][j]

[[9, 5, 1], 
[10, 6, 2], 
[11, 7, 3], 
[12, 8, 4]]