from reportlab.pdfgen import canvas
from reportlab.lib.pagesizes import A4
from reportlab.lib.units import mm

c = canvas.Canvas("hello.pdf", pagesize=A4)

width, height = A4
numv = int((width - ((4 + 4) * mm)) / (5 * mm))
numh = int((height / 2.0 - ((12.5 + 2) * mm)) / (5 * mm))
voff = (width - numv * 5 * mm) / 2.0
hoff = height / 2 - (12.5 + numh * 5) * mm

# Draw grid
c.setLineWidth(0.15)
c.setStrokeColorRGB(0.5, 0.5, 1)
for xi in xrange(numv + 1):
    c.line(xi * mm * 5 + voff, hoff,
           xi * mm * 5 + voff, hoff + numh * mm * 5)
    c.line(xi * mm * 5 + voff, height - hoff,
           xi * mm * 5 + voff, height - (hoff + numh * mm * 5))

for yi in xrange(numh + 1):
    c.line(voff, hoff + yi * mm * 5,
           voff + numv * mm * 5, hoff + yi * mm * 5)
    c.line(voff, height - (hoff + yi * mm * 5),
           voff + numv * mm * 5, height - (hoff + yi * mm * 5))

# Draw horizontal center
c.setDash(1)
c.setStrokeColorRGB(0.5, 0.5, 1)
c.circle(width / 2, height / 2 + 1.5 * mm, 0.5, fill=1)
c.circle(width / 2, height / 2 - 1.5 * mm, 0.5, fill=1)

# Draw splitter
c.setDash([3, 3])
c.setStrokeColorRGB(0.4, 0.4, 0.4)
c.line(0, height / 2, width, height / 2)

c.save()