def drillPath(diameter):

    r = diameter/2.0

    # The calculation to obtain the 'k' coefficient can be found here:
    # http://itc.ktu.lt/itc354/Riskus354.pdf
    # "APPROXIMATION OF A CUBIC BEZIER CURVE BY CIRCULAR ARCS AND VICE VERSA"
    # by Aleksas Riskus
    k = 0.5522847498

    # internal circle
    b = r*0.9

    return "m %s,%s c %s,%s %s,%s %s,%s %s,%s %s,%s %s,%s %s,%s %s,%s %s,%s %s,%s %s,%s %s,%s z m %s,%s %s,%s c %s,%s %s,%s %s,%s l %s,%s %s,%s c %s,%s %s,%s %s,%s z" % (0,r, k*r,0, r,-r*(1-k), r,-r, 0,-r*k, -r*(1-k),-r, -r,-r, -r*k,0, -r,r*(1-k), -r,r, 0,r*k, r*(1-k),r, r,r, 0,-(r-b), 0,-2*b, -b*k,0, -b,b*(1-k), -b,b, b,0, b,0, 0,k*b, -b*(1-k),b, -b,b)
Returns an SVG path for a drill symbol of diameter 'diameter'
dataset/ETHPy150Open boldport/pcbmode/pcbmode/utils/svg.py/drillPath