from turtle import *

t=50
sz=8
black=True

speed('fastest')
shape('turtle')

setup(t*(sz+2),t*(sz+4))

up()
goto(-t*sz/2,-t*sz/2)

for k in range(sz):
  down()
  for j in range(sz):
    if black: color('black')
    else: color('red')
    fill(True)
    for i in range(4):
      forward(t)
      right(90)
    fill(False)
    forward(t)
    black=not black
  up()
  backward(sz*t)
  left(90)
  forward(t)
  right(90)
  if sz%2==0:
    black=not black

color('purple')

exitonclick()