curriculum/challenges/english/blocks/learn-classes-and-objects-by-building-a-sudoku-solver/6606d8c323d6205890fbbd54.md
Within the Board class, create another method is_valid and give it three parameters: self, empty, and num. Where empty is a tuple representing the row and column indices of an empty cell and num is the number to be checked.
This method will check if a given number is a valid choice for an empty cell in the sudoku board by validating its compatibility with the row, column, and 3x3 square of the specified empty cell.
You should create a new method named is_valid within the Board class.
({ test: () => assert(runPython(`_Node(_code).find_class("Board").has_function("is_valid")`)) })
Your is_valid method should have three parameters: self, empty, and num, in this order.
({ test: () => assert(runPython(`_Node(_code).find_class("Board").find_function("is_valid").has_args("self, empty, num")`)) })
class Board:
def __init__(self, board):
self.board = board
def find_empty_cell(self):
for row, contents in enumerate(self.board):
try:
col = contents.index(0)
return row, col
except ValueError:
pass
return None
def valid_in_row(self, row, num):
return num not in self.board[row]
def valid_in_col(self, col, num):
return all(self.board[row][col] != num for row in range(9))
def valid_in_square(self, row, col, num):
row_start = (row // 3) * 3
col_start = (col // 3) * 3
for row_no in range(row_start, row_start + 3):
for col_no in range(col_start, col_start + 3):
if self.board[row_no][col_no] == num:
return False
return True
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puzzle = [
[0, 0, 2, 0, 0, 8, 0, 0, 0],
[0, 0, 0, 0, 0, 3, 7, 6, 2],
[4, 3, 0, 0, 0, 0, 8, 0, 0],
[0, 5, 0, 0, 3, 0, 0, 9, 0],
[0, 4, 0, 0, 0, 0, 0, 2, 6],
[0, 0, 0, 4, 6, 7, 0, 0, 0],
[0, 8, 6, 7, 0, 4, 0, 0, 0],
[0, 0, 0, 5, 1, 9, 0, 0, 8],
[1, 7, 0, 0, 0, 6, 0, 0, 5]
]
gameboard = Board(puzzle)