I would like to do this elegantly, where my last return looks like that:

return "(x{:+.2f})^2+(y{:+.2f})^2={:.2f}^2".format(-round(middle[0], 2), -round(middle[1], 2), round(distance((points[2], middle)), 2))

This would be allright if not the fact, that {.2f} is fixed formatting of 2 digits behind the point. What should I use to get not exactly, but only if needed 2 digits behind the point? It's hard for me to google it out.

 Your result: "(x-3.00)^2+(y-3.00)^2=1.41^2"
 Right result: "(x-3)^2+(y-3)^2=1.41^2"

:C