from collections import namedtuple
from itertools import product

Coordinate = namedtuple('Coordinate', 'row column')
GRID_MIN = Coordinate(ord('A'), 0)
GRID_MAX = Coordinate(ord('Y'), 24)


def get_local_grid(coordinate):
    for relative_row, relative_column in product(range(-1, 2), range(-1, 2)):
        absolute_row = coordinate.row + relative_row
        absolute_column = coordinate.column + relative_column
        yield Coordinate(absolute_row, absolute_column)


def get_surrounding_coordinates(coordinate):
    for local_coordinate in get_local_grid(coordinate):
        if is_on_grid(local_coordinate) and local_coordinate != coordinate:
            yield local_coordinate


def get_neighbors(letter_coordinate):
    coordinate = make_numeric_coordinate(letter_coordinate)
    return [make_letter_coordinate(coordinate) for coordinate in get_surrounding_coordinates(coordinate)]


def is_on_grid(coordinate):
    return is_valid_row(coordinate) and is_valid_column(coordinate)


def is_valid_row(coordinate):
    return GRID_MIN.row <= coordinate.row <= GRID_MAX.row


def is_valid_column(coordinate):
    return GRID_MIN.column <= coordinate.column <= GRID_MAX.column


def make_numeric_coordinate(letter_coordinate):
    return Coordinate(ord(letter_coordinate[0]), int(letter_coordinate[1:]))


def make_letter_coordinate(coordinate):
    return f"{chr(coordinate.row)}{coordinate.column}"