数组初始化的一个问题

https://leetcode-cn.com/problems/valid-sudoku/submissions/
做这个的时候发现一个特别奇怪的事情，我在初始化数组时，有两种相同结果的初始方式去做，但是有个就是不对。。。

class Solution:
    def isValidSudoku(self, board: List[List[str]]) -> bool:
        row= [[0] * 9 for _ in range(9)]
        col= [[0] * 9 for _ in range(9)]
        box= [[0] * 9 for _ in range(9)]
        for i in range(9):
            for j in range(9):
                if board[i][j]=='.':
                    continue
                num=ord(board[i][j]) - ord('0')-1
                if row[i][num] != 0 or col[j][num] != 0 or box[j//3+(i//3)*3][num] != 0:
                    return False
                row[i][num], col[j][num], box[j//3+(i//3)*3][num]=1,1,1
        return True

class Solution:
    def isValidSudoku(self, board: List[List[str]]) -> bool:
        row=  [[0]*9]*9
        col=  [[0]*9]*9
        box=  [[0]*9]*9
        for i in range(9):
            for j in range(9):
                if board[i][j]=='.':
                    continue
                num=ord(board[i][j]) -ord('0')-1
                if row[i][num] != 0 or col[j][num] != 0 or box[j//3+(i//3)*3][num] != 0:
                    return False
                row[i][num], col[j][num], box[j//3+(i//3)*3][num]=1,1,1
        return True

结果就不对了

明明这两种方式返回的数组时一样的啊，无语