board-py

def print_board(board):
    for i in range(9):
        for j in range(9):
            print(board[i][j], end=" ")
        print()

def find_empty(board):
    for i in range(9):
        for j in range(9):
            if board[i][j] == 0:
                return i, j
    return None

def is_valid(board, num, pos):
    for i in range(9):
        if board[pos[0]][i] == num or board[i][pos[1]] == num:
            return False
    box_x = pos[1] // 3
    box_y = pos[0] // 3
    for i in range(box_y * 3, box_y * 3 + 3):
        for j in range(box_x * 3, box_x * 3 + 3):
            if board[i][j] == num:
                return False
    return True

def solve(board):
    find = find_empty(board)
    if not find:
        return True
    row, col = find
    for i in range(1, 10):
        if is_valid(board, i, (row, col)):
            board[row][col] = i
            if solve(board):
                return True
            board[row][col] = 0
    return False

board = [
    [5, 3, 0, 0, 7, 0, 0, 0, 0],
    [6, 0, 0, 1, 9, 5, 0, 0, 0],
    [0, 9, 8, 0, 0, 0, 0, 6, 0],
    [8, 0, 0, 0, 6, 0, 0, 0, 3],
    [4, 0, 0, 8, 0, 3, 0, 0, 1],
    [7, 0, 0, 0, 2, 0, 0, 0, 6],
    [0, 6, 0, 0, 0, 0, 2, 8, 0],
    [0, 0, 0, 4, 1, 9, 0, 0, 5],
    [0, 0, 0, 0, 8, 0, 0, 7, 9]
]

solve(board)
print_board(board)