trying out sudoku

sudoku.py

import sys
import random

def main():
    generate_sudoku()
    initial_state = load_sudoku()
    sudoku = Sudoku(initial_state)
    print(sudoku)

def generate_sudoku():
    with open('sudoku.txt','w') as sudoku_file:
        blueprint = ('{},'*8 + '{} \n')*9
        state = fill_slots()
        sudoku_file.write(blueprint.format(*state))
  

def relatives(slot):
    row = slot // 9
    row_relatives = [row*9+i for i in range(9)]
    #print(row)
    
    column = slot % 9
    column_relatives = [i+column for i in range(0,81,9)]
    #print(column)
    
    box = (row - row % 3)*9 + (column - column % 3)
    #box_relatives = [box, box+1, box+2, box+9, box+10, box+11, box+18, box+19, box+20]
    box_relatives = [box + row + column * 9 for row in range(3) for column in range(3)]
    #print(box)

    return set(row_relatives +  box_relatives +  column_relatives)   

def fill_slots():
    state = [0] * 81
    slots = set([random.randint(0,80) for _ in range(36)])
    for slot in slots:
        state[slot] = random.randint(1,9)
        for relative in relatives(slot) & slots:
            while slot != relative and state[slot] == state[relative]:
                state[slot] = random.randint(1,9)
    #for relative in relatives(4):
        #state[relative] = random.randint(1,9)
    return state

    

def load_sudoku():
    if len(sys.argv) > 1:
        raw = read_file(sys.argv[1])
    else:
        raw = request_file()
    
    return raw

def read_file(fname):
    try:
        arr = []
        with open(fname, 'r') as sudoku_file:
            arr = [int(row) for line in sudoku_file for row in line.strip().split(',')]
    except Exception as e:
        print("Couldn't read file {}. msg: {}".format(fname,e))
        arr = request_file()
    return arr

def request_file():
    fname = input("Enter location of file containing the Sudoku puzzle:")
    return read_file(fname)

class Sudoku:
    def __init__(self, initial_state):
        self.view = initial_state

    def __str__(self):
        template = ("{} | {} | {} || {} | {} | {} || {} | {} | {}\n" + '-' * 35 + '\n') * 9
        return template.format(*self.view)

if __name__ == '__main__':
    main()