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

transpose = [[ligne[element] for ligne in matrice] for element in range(len(matrice[0]))]
 
print(transpose)
'''
[[1, 5, 9], [2, 6, 10], [3, 7, 11], [4, 8, 12]]
'''