title: How to do a Sigma in python 3
body: <p>I'm trying to make a calculator for something, but the formulas use a sigma, I have no idea how to do a sigma in python, is there an operator for it?
  Ill put a link here with a page that has the formulas on it for illustration:<a href="http://fromthedepths.gamepedia.com/User:Evil4Zerggin/Advanced_cannon" rel="nofollow">http://fromthedepths.gamepedia.com/User:Evil4Zerggin/Advanced_cannon</a></p>