range与剩余切片结合：
arr = [[8, 9],[0, 1, 2, 3],[3, 4, 5, 6, 7],[2, 3, 4, 9]]
arr = [list(range(0, a[0]+1)) + a[1:] for a in arr]
[[0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
[0, 1, 2, 3],
[0, 1, 2, 3, 4, 5, 6, 7],
[0, 1, 2, 3, 4, 9]]使 python 数组中的每个成员都以零开头
range与剩余切片结合：
arr = [[8, 9],[0, 1, 2, 3],[3, 4, 5, 6, 7],[2, 3, 4, 9]]
arr = [list(range(0, a[0]+1)) + a[1:] for a in arr]
[[0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
[0, 1, 2, 3],
[0, 1, 2, 3, 4, 5, 6, 7],
[0, 1, 2, 3, 4, 9]]