sudoku solver using backtracking algorithm

sudoku_solver.py

def print_grid(grid):
    for i in range(9):
        for j in range(9):
            print(grid[i][j], end="")
        print('\n')

def find_empty_location(grid):
    for row in range(9):
        for column in range(9):
            if grid[row][column] == 0:
                return [row, column]

    return False


def check_is_safe(row, num):
    for field in row:
        if num == field:
            return False

    return True

def check_box_is_safe(box, num):
    for i in range(3):
        for j in range(3):
            if box[i][j] == num:
                return False

    return True

def location_is_safe(num, location, grid):
    row_index, column_index = location

    row = [item for item in grid[row_index]]

    if not check_is_safe(row, num):
        return False

    column = [grid[index][column_index] for index in range(9)]

    if not check_is_safe(column, num):
        return False

    box_row_index = row_index - row_index % 3
    box_column_index = column_index - column_index % 3

    box = [row[box_column_index:box_column_index + 3] for row in grid[box_row_index:box_row_index + 3]]

    if not check_box_is_safe(box, num):
        return False

    return True


def solve(grid):
    location = find_empty_location(grid)

    # all fields are filled - done
    if not location:
        return True

    for num in range(1, 10):
        if location_is_safe(num, location, grid):
            row_index, column_index = location
            grid[row_index][column_index] = num

            if solve(grid):
                return True

            grid[row_index][column_index] = 0

    # backtracking
    return False


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

if solve(grid):
    print_grid(grid)
else:
    print("No solution found")