Can this Iron Python 2.7 code be sped up? - python-2.7

Question

I have implemented Gray-Scott reaction diffusion in Iron Python 2, mapping grayscale values between 0 and 1.
But since it only gets interesting from about 6400 steps, it takes a lot of time.
So can someone smarter / more proficient in Python than me help me make this code more efficient?
Here is the code:
import random as rnd
dA = 1
dB = 0.5
feed = 0.055
kill = 0.062
wHalb = int(width/2)
hHalb = int(height/2)
#decides if gAA is random or 1
if gAA == 0:
gAA = rnd.random()
def main():
#create base grid of chemical A and B
gridA = [ [gAA for i in range(width)] for i in range(height)]
gridB = [ [0 for i in range(width)] for i in range(height)]
nextA = [ [1 for i in range(width)] for i in range(height)]
nextB = [ [0 for i in range(width)] for i in range(height)]
color = [ [0 for i in range(width)] for i in range(height)]
for x in range (wHalb-baseBlock,wHalb+baseBlock):
for y in range (hHalb-baseBlock,hHalb+baseBlock):
gridB[x][y] = 1
x, y, i, j = 0, 0, 0, 0
for n in range(steps):
for x in range (width):
for y in range (height):
a = gridA[x][y]
b = gridB[x][y]
nextA[x][y] = (a + (dA * laplaceA(x, y, gridA)) - (a * b*b) + (feed * (1 - a)))
nextB[x][y] = (b + (dB * laplaceB(x, y, gridB)) + (a * b*b) - ((kill + feed) * b))
tempA = gridA
gridA = nextA
nextA = tempA
tempB = gridB
gridB = nextB
nextB = tempB
color = [ [(nextA[i][j] - nextB[i][j]) for i in range(width)] for j in range(height)]
return color
def laplaceA(x, y, gridA):
sumA = 0;
xS = x - 1
xE = x + 1
yS = y - 1
yE = y + 1
if (x == 0):
xS = width-1
if (y == 0):
yS = height-1
if (x == width - 1):
xE = 0;
if (y == height - 1):
yE = 0;
sumA = sumA + gridA[x][y] * -1
sumA = sumA + gridA[xS][y] * 0.2
sumA = sumA + gridA[xE][y] * 0.2
sumA = sumA + gridA[x][yE] * 0.2
sumA = sumA + gridA[x][yS] * 0.2
sumA = sumA + gridA[xS][yS] * 0.05
sumA = sumA + gridA[xE][yS] * 0.05
sumA = sumA + gridA[xS][yE] * 0.05
sumA = sumA + gridA[xE][yE] * 0.05
return sumA
def laplaceB(x, y, gridB):
sumB = 0
xS = x - 1
xE = x + 1
yS = y - 1
yE = y + 1
if (x == 0):
xS = width-1
if (y == 0):
yS = height-1
if (x == width - 1):
xE = 0
if (y == height - 1):
yE = 0
sumB = sumB + gridB[x][y] * -1
sumB = sumB + gridB[xS][y] * 0.2
sumB = sumB + gridB[xE][y] * 0.2
sumB = sumB + gridB[x][yE] * 0.2
sumB = sumB + gridB[x][yS] * 0.2
sumB = sumB + gridB[xS][yS] * 0.05
sumB = sumB + gridB[xE][yS] * 0.05
sumB = sumB + gridB[xS][yE] * 0.05
sumB = sumB + gridB[xE][yE] * 0.05
return sumB
aOut = main()