Making word wheels

$ python make_word_wheel.py eeialctrh >wordwheel.svg

import sys
import math

try:
    letters = sys.argv[1]
except IndexError:
    print('usage: {} <letters>'.format(sys.argv[0]))
    print('The central letter should be given first.')
    sys.exit(1)

# The coordinates of the centre of the 300x300 image
cx, cy = 150, 150

# SVG preamble and styles
print("""<?xml version="1.0" encoding="utf-8"?>

<svg xmlns="http://www.w3.org/2000/svg"
     xmlns:xlink="http://www.w3.org/1999/xlink" width="300" height="300" >
<defs>
<style type="text/css"><![CDATA[

circle {
    fill: #fff;
    stroke: #000;
    stroke-width: 3px;
}
.central_circle {
    fill: #000;
}
text {
    font-size: 18pt;
    font-family: sans-serif;
    text-anchor: middle;
    dominant-baseline: middle;
}
text.central_letter {
    fill: #fff;
    stroke: #fff;
}

]]></style>
</defs>
""")

# The central letter
print('<circle cx="150" cy="150" r="30" class="central_circle"/>')
print('<text x="150" y="150" class="central_letter">{}</text>'
            .format(letters[0].upper()))

# The surrounding letters.
m = len(letters)-1
for i in range(0, m):
    letter = letters[i+1].upper()
    x = cx + 85*math.cos(i * 2*math.pi/m)
    y = cy + 85*math.sin(i * 2*math.pi/m)
    print('<circle cx="{}" cy="{}" r="30"/>'.format(x, y))
    print('<text x="{}" y="{}">{}</text>'.format(x, y, letter))

# Close tag and we're done.
print('</svg>')