Conway's Game of Life Python Numpy TKinter

"""
lifecartoon.py, made with help from http://en.wikipedia.org/wiki/Conway's_Game_of_Life
"""
from numpy import zeros
from Tkinter import *

window = Tk()
canvas = Canvas(window, width = 800, height = 800)
canvas.pack()

def aliveneighbourcounter(y,x):     # counts the number of alive neighbours (wraps around canvas edges)
    ancounter = 0
    if y==0: yminus1 = len(grid)-1
    else: yminus1 = y-1
    if y==len(grid)-1: yplus1 = 0
    else: yplus1 = y+1
    if x==0: xminus1 = len(grid)-1
    else: xminus1 = x-1
    if x==len(grid)-1: xplus1 = 0
    else: xplus1 = x+1
    if grid[yminus1][xminus1] == 1: ancounter += 1
    if grid[y][xminus1] == 1: ancounter += 1
    if grid[yminus1][x] == 1: ancounter += 1
    if grid[y][xplus1] == 1: ancounter += 1
    if grid[yplus1][x] == 1: ancounter += 1
    if grid[yplus1][xplus1] == 1: ancounter += 1
    if grid[yplus1][xminus1] == 1: ancounter += 1
    if grid[yminus1][xplus1] == 1: ancounter += 1
    return ancounter

def kill(grid):             # kills if the number of alive neighbours is other than 2 or 3
    gridkilled = zeros([40,40])
    for y in range(len(grid)):
        for x in range(len(grid)):
          gridkilled[y][x] = grid[y][x]
          if grid[y][x] == 1:
            ancounter = aliveneighbourcounter(y,x)
            if ancounter<2 or ancounter>3:
                gridkilled[y][x] = 0
    return gridkilled

def cometolife(grid):           # brings to life if there are exactly 3 alive neighbours
    gridcametolife = zeros([40,40])
    for y in range(len(grid)):
        for x in range(len(grid)):
          if grid[y][x] == 0:
            ancounter = aliveneighbourcounter(y,x)
            if ancounter == 3:
                gridcametolife[y][x] = 1
    return gridcametolife

def drawbox():              # draws a blue box for 'alive', a green box for 'dead'
    for y in range(len(grid)):
        for x in range(len(grid)):
          if grid[y][x] == 1:
            canvas.create_rectangle(20*x, 20*y, 20*x+20, 20*y+20, fill="#220C65", outline="#DFF2A6", width=1)
          elif grid[y][x] == 0:
            canvas.create_rectangle(20*x, 20*y, 20*x+20, 20*y+20, fill="#A4AD90", outline="#DFF2A6", width=1)

# set up the initial state of the system (0 means 'dead', 1 means 'alive'):
grid = zeros([40,40])
grid[35][37] = grid[35][38] = grid[35][39] = 1                      # blinker
grid[7][3] = grid[7][4] = grid[7][5] = grid[8][4] = grid[8][5] = grid[8][6] = 1     #toad
grid[20][20] = grid[21][20] = grid[22][20] = grid[22][21] = grid[21][22] = 1        # glider
grid[30][30] = grid[31][30] = grid[32][30] = grid[33][30] = grid[30][31] = grid[30][32] = grid[31][33] = grid[34][31] = grid[34][33] = 1 #lwss

# animation loop:
while 1==1:
    gridkilled = kill(grid)
    gridcametolife = cometolife(grid)
    for y in range(len(grid)):
        for x in range(len(grid)):
            if gridkilled[y][x] == gridcametolife[y][x] == 1:
                grid[y][x] = 1
            else:
                grid[y][x] = gridkilled[y][x] + gridcametolife[y][x]
    drawbox()
    canvas.after(30)
    canvas.update()

window.mainloop()