Проблема с реализацией Python игры Конвея "Игра жизни"

Я работаю над Игра жизни Конвея в настоящее время и застрял. Мой код не работает.

Когда я запускаю свой код в графическом интерфейсе, он говорит:

 
[[0 0 0 0]
 [0 1 1 0]
 [0 1 0 0]
 [0 0 0 0]]

Traceback (most recent call last):
  File "C:\Users\Documents\Physics\Python\MainProject\conway.py", line 53, in 
    b= apply_rules(a)
  File "C:\Users\Documents\Physics\Python\MainProject\conway.py", line 14, in apply_rules
    neighbours=number_neighbours(universe_array,iy,ix)
  File "C:\Users\Documents\Physics\Python\MainProject\conway.py", line 36, in number_neighbours
    neighbours+=1
UnboundLocalError: local variable 'neighbours' referenced before assignment

Вот мой код:

'''If a cell is dead at time T with exactly three live neighbours, the cell will be alive at T+1
If a cell is alive at time T with less than two living neighbours it dies at T+1
If a cell is alive at time T with more than three live neighbours it dies at T+1
If a cell is alive at time T with exactly two or three live neighbours it remains alive at T+1'''
import numpy


def apply_rules (universe_array):
    height, width = universe_array.shape
    # create a new array for t+1
    evolved_array = numpy.zeros((height, width),numpy.uint8)
    for iy in range(1, height-1):
        for ix in range(1,width-1):
            neighbours=number_neighbours(universe_array,iy,ix)
            if universe_array[iy,ix]==0 and neighbours==3:
                evolved_array[iy,ix]==1
            elif universe_array[iy,ix]==1 and neighbours<2:
                evolved_array[iy,ix]==0
            elif universe_array[iy,ix]==1 and neighbours>3:
                evolved_array[iy,ix]==0
            elif universe_array[iy,ix]==1 and neighbours==2 or neighbours==3:
                evolved_array[iy,ix]=universe_array[iy,ix]

    return evolved_array

def number_neighbours(universe_array,iy,ix):
    neighbours=0 #fixed this line,thanks:)
    if universe_array[iy-1,ix-1]==1:
            neighbours+=1
    if universe_array[iy,ix-1]==1:
            neighbours+=1
    if universe_array[iy+1,ix-1]==1:
            neighbours+=1
    if universe_array[iy-1,ix]==1:
            neighbours+=1
    if universe_array[iy+1,ix]==1:
            neighbours+=1
    if universe_array[iy-1,ix+1]==1:
            neighbours+=1
    if universe_array[iy,ix+1]==1:
            neighbours+=1
    if universe_array[iy+1,ix+1]==1:
            neighbours+=1
    else:
        neighbours=neighbours
    return neighbours

if __name__ == "__main__":
    a = numpy.zeros((4,4),numpy.uint8)
    a[1,1]=1
    a[1,2]=1
    a[2,1]=1
    print a
    b= apply_rules(a)
    print b

Я новичок в Python и не знаю, как исправить ошибку. Я немного сбит с толку по поводу import "neighbours" и function "apply_rules", это правильный способ сделать это?