矩阵，转置矩阵

转置方阵

l=[[1,2,3],[4,5,6],[7,8,9]]
for i in range(3):
    for j in range(3):
        if i>j:
            l[i][j], l[j][i] = l[j][i], l[i][j]
print(l)

对角线的一半与另一半交换位置

转置矩阵

l=[[1,2,3],[4,5,6]]
n=[]
for i in range(3):
    n.append([])
    for j in range(2):
        n[i].append(0)
for i in range(3):
    for j in range(2):
        n[i][j]=l[j][i]
print(n)

将以上for循环写成列表解析式

l=[[1,2,3],[4,5,6]]
n=[[0 for i in range(2)]for i in range(3)]
for i in range(len(n)):
    for j in range(len(n[0])):
        n[i][j]=l[j][i]
print(n)

解析式的输出为

n=[[0 for i in range(2)]for i in range(3)]
n

[[0, 0], [0, 0], [0, 0]]