polycircles.py

polycircles.py

import math
import cmath

def main():
    end = 500
    size = 800.0
    r = size / 2 / 9
    dash = 5

    limit = r * 8.7
    center = (size / 2.0) * (1 + 1j)
    fmt = lambda w: f'fill="none" stroke="black" stroke-width="{w}"'
    fmt_limit = f'fill="none" stroke="green" stroke-width="1" stroke-dasharray="{dash} {dash}"'

    yield f'<svg version="1.1" width="{size}" height="{size}" xmlns="http://www.w3.org/2000/svg">'
    yield '<rect x="0" y="0" width="100%" height="100%" fill="white" />'

    yield f'<polyline points="{center.real} {center.imag - r} {center.real} {center.imag + r}" {fmt(1)}/>'

    yield f'<circle cx="{center.real}" cy="{center.imag}" r="{r}" {fmt(1)}/>'
    for n in range(3, end):
        r /= math.cos(math.pi / n)
        w = 1 / (1 + n ** 1.5 / 100)
        pts = [center + cmath.rect(r, math.tau * i / n - math.pi / 2) for i in range(n)]
        pts = ' '.join(str(p) for pt in pts for p in (pt.real, pt.imag))
        yield f'<polygon points="{pts}" {fmt(w)}/>'
        yield f'<circle cx="{center.real}" cy="{center.imag}" r="{r}" {fmt(w)}/>'
    yield f'<circle cx="{center.real}" cy="{center.imag}" r="{limit}" {fmt_limit}/>'

    yield '</svg>'

print('\n'.join(main()))