Donut chart generator

donutchart.py

from math import cos, sin, radians


def piechart(data, width=100, height=100, stroke=40):
	center_x = width / 2
	center_y = height / 2
	radius = min([center_x, center_y]) - 5

	paths = []

	sum_ = sum(data.keys())

	dx = radius
	dy = _angle = 0

	for value, color in data.iteritems():

		angle = _angle + value / (sum_ / 360.0)

		x = cos(radians(angle)) * radius
		y = sin(radians(angle)) * radius

		abs_x, abs_y = center_x + x, center_y + y
		abs_dx, abs_dy = center_x + dx, center_y + dy

		paths.append(
			"""
				<path
					d="M{cx},{cy} L{adx},{ady} A{r},{r} 0 {la},1 {ax},{ay}z"
					fill="{c}"
				/>
			""".format(
				cx=center_x,
				cy=center_y,
				adx=abs_dx,
				ady=abs_dy,
				r=radius,
				la=int(value > sum_ / 2.0),
				ax=abs_x,
				ay=abs_y,
				c=color)
		)

		dx, dy = x, y

		_angle = angle

	paths.append("""
		<circle cx="{cx}" cy="{cy}" r="{r}" fill="white" />
		""".format(cx=center_x, cy=center_y, r=radius - stroke)
	)
	return ''.join(paths)

data = {
	20: 'red',
	70: 'blue',
	15: 'orange',
	38: 'green'
}
width = height = 400

chart = """
	<svg width="{width}px" height="{height}px" xmlns="http://www.w3.org/2000/svg">
		{piechart}
	</svg>
""".format(width=width, height=height, piechart=piechart(data, width, height, 40))

with open('chart.svg', 'w') as out:
	out.write(chart)