Yesterday I was showing my wife how does a computer program works, so I end up with this code

gol.py

#coding: utf-8

"""
    Conway's Game of Life implementation with console interface
    Author: Antonio Ribeiro - [email protected]
    license: Do What You Want to
"""

from time import sleep
from random import randint


def ppp(p):
    """Print the board on the screen"""
    l = len(p)
    print '--'*(l+1) + '-'
    for i in xrange(l):
        print '|',
        for j in xrange(l):
            if p[i][j]:
                print '■',
            else:
                print ' ',
        print '|'
    print '--'*(l+1) + '-'


def get_board(l=10, fill=lambda : 0):
    p = []
    for i in range(l):
        line = [fill() for i in xrange(l)]
        p.append(line)
    return p

def get_neighbours(p, i, j):
    n = 0
    l = len(p)-1
    for a in [-1, 0, 1]:
        for b in [-1, 0, 1]:
            if a+i < 0 or b+j < 0 or a+i > l or b+j > l or a == b == 0:
                continue
            if p[i+a][j+b]:
                n += 1
    
    if p[i][j] and n < 2 or n > 3:
        return 0
    elif n == 3:
        return 1
    else:
        return p[i][j]


def step(p):
    l = len(p)
    new_p = get_board(l)
    for i in xrange(l):
        for j in xrange(l):
            new_p[i][j] = get_neighbours(p, i, j)

    return new_p


if __name__ == '__main__':
    l = 80
    p = get_board(l, fill=lambda : randint(0,1))
    while True:
        ppp(p)
        p = step(p)
        sleep(0.2)

gol_interface.py

#coding: utf-8
#!/usr/bin/env pytHEIGHTon
 
"""
    A Pygame interface for Conway's Game of Life
    Keys:
        <SPACE> - Pause/resume running
        <KEY_UP>/<KEY_DOWN> - increase/decrease speed
        <KEY_LEFT>/<KEY_RIGHT> - advance/return one single step
    Author: Antonio Ribeiro - [email protected]
    license: Do What You Want to
"""

import pygame
from time import sleep
from random import randint
import gol

MAGNIFY = 5
WEIGHT = HEIGHT = 100

class Buffer(object):
    """ Just a simple FILO stack"""

    def __init__(self, max_len=150):
        self.max_len = max_len
        self._buffer = []

    def put(self, frame):
        if len(self._buffer) == self.max_len:
            self._buffer.pop(-1)

        self._buffer.insert(0,frame)

    def pop(self):
        return self._buffer.pop(0)


def put_point(screen, i, j, color=(255, 255, 255)):
    i *= MAGNIFY
    j *= MAGNIFY
    pygame.draw.rect(screen, color, (i, j, MAGNIFY, MAGNIFY), 0)


def clear_screen(screen):
    pygame.draw.rect(screen, (0,0,0), (0,0,WEIGHT*MAGNIFY,HEIGHT*MAGNIFY), 0)


def print_board(screen, p):
    l = len(p)
    for i in range(l):
        for j in range(l):
            if p[i][j]:
                put_point(screen, i, j)


def main():
    
    running = True
    paused = False
    delay = 0.1
    
    screen = pygame.display.set_mode((WEIGHT*MAGNIFY, HEIGHT*MAGNIFY))
    bfr = Buffer()
    
    p = gol.get_board(WEIGHT, fill=lambda : randint(0,1))
    bfr.put(p)
    
    while running:

        if not paused:
            clear_screen(screen)
            print_board(screen, p)
            pygame.display.flip()
            p = gol.step(p)
            bfr.put(p)
            if delay > 0.0:
                sleep(delay)

        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                running = False
            elif event.type == pygame.KEYDOWN:
                if event.key == pygame.K_DOWN:
                    if delay < 1.0:
                        delay += 0.1
                elif event.key == pygame.K_UP:
                    if delay > 0.0:
                        delay -= 0.1
                elif event.key == pygame.K_SPACE:
                    paused = not paused
                
                elif event.key == pygame.K_LEFT:
                    paused = True
                    try:
                        p = bfr.pop()
                    except IndexError:
                        continue
                    clear_screen(screen)
                    print_board(screen, p)
                    pygame.display.flip()

                elif event.key == pygame.K_RIGHT:
                    paused = True
                    bfr.put(p)
                    p = gol.step(p)
                    clear_screen(screen)
                    print_board(screen, p)
                    pygame.display.flip()

if __name__ == '__main__':
    main()