# grid

# ch31_4.py
import turtle
a,b = -365,-300
n = 600
step = 20
t = turtle.Pen()
t.speed(0)
t.width(0.1)
t.hideturtle()
for i in range(0, n+step, step):
    t.penup()
    t.setpos(i+a,b)
    t.pendown()
    t.setpos(a, n-i+b)
#turtle.done()
t = turtle.getscreen()
t.getcanvas().postscript(file='grid.eps')