无法使用python创建数独级别

def solve_sudoku(board):
    # 定义一个辅助函数，用于检查某个位置是否可以填入指定的数字
    def is_valid(board, row, col, num):
        # 检查当前行是否有重复数字
        for i in range(9):
            if board[row][i] == num:
                return False
        # 检查当前列是否有重复数字
        for i in range(9):
            if board[i][col] == num:
                return False
        # 检查当前小格子是否有重复数字
        start_row = (row // 3) * 3
        start_col = (col // 3) * 3
        for i in range(3):
            for j in range(3):
                if board[start_row + i][start_col + j] == num:
                    return False
        return True

    # 定义一个辅助函数，用于查找下一个需要填入数字的位置
    def find_empty(board):
        for i in range(9):
            for j in range(9):
                if board[i][j] == 0:
                    return i, j
        return -1, -1

    # 主函数，使用递归和回溯算法来解决数独问题
    def solve(board):
        row, col = find_empty(board)
        if row == -1 and col == -1:
            return True
        for num in range(1, 10):
            if is_valid(board, row, col, num):
                board[row][col] = num
                if solve(board):
                    return True
                board[row][col] = 0
        return False

    # 调用主函数来解决数独问题
    solve(board)

# 创建一个空的数独棋盘
board = [
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0]
]

# 调用函数来解决数独问题
solve_sudoku(board)

# 打印解决后的数独棋盘
for i in range(9):
    for j in range(9):
        print(board[i][j], end=" ")
    print()