定义一个5行5列的二维整形数组，将每一列的最大值输出。每个最值用空格隔开，最后一个最值后面也有空格

arr = [[1, 2, 3, 4, 5], 
 [6, 7, 8, 9, 10], 
       [11, 12, 13, 14, 15], 
       [16, 17, 18, 19, 20], 
       [21, 22, 23, 24, 25]]

for j in range(len(arr[0])):
    max_val = arr[0][j]
    for i in range(len(arr)):
        if arr[i][j] > max_val:
            max_val = arr[i][j]
    print(max_val, end=' ')

输出：

21 22 23 24 25