conway.py

from itertools import product

def count_neighbours(x, y):
    deltas = set(product((-1, 0, 1), repeat=2)) - {(0, 0)}
    return len({(x + dx, y + dy) for (dx, dy) in deltas} & lights_on)

def evolve(lights_on):
    still_on = {(x, y) for x, y in lights_on if count_neighbours(x, y) in (2, 3)}
    now_off = set(product(range(SIZE), repeat=2)) - lights_on
    turn_on = {(x, y) for x, y in now_off if count_neighbours(x, y) == 3}
    return still_on | turn_on

def print_grid():
    for y in range(SIZE):
        print(''.join('#' if (x, y) in lights_on else ' ' for x in range(SIZE)))

SIZE = 10
lights_on = {(1, 1), (2, 1), (3, 1)}
print_grid()
for i in range(100):
    lights_on = evolve(lights_on)
    print_grid()