Question: 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:<http://fromthedepths.gamepedia.com/User:Evil4Zerggin/Advanced_cannon>

Answer: 
I've looked all the answers that different programmers and coders have tried to give to your query but i was unable to understand any of them maybe because i am a high school student anyways according to me using LIST will definately reduce some pain of coding so here it is what i think simplest way to form a sigma function .

```
#creating a sigma function
a=int(input("enter a number for sigma  "))
mylst=[]

for i in range(1,a+1):
     mylst.append(i)
     b=sum(mylst)
print(mylst)
print(b)

```
```
import numpy as np

def sigma(s,e):
  x = np.arange(s,e)
  return np.sum([x+1])

```