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: 
The easiest way to do this is to create a sigma function the returns the summation, you can barely understand this, you don't need to use a library. you just need to understand the logic .

```py
def sigma(first, last, const):
    sum = 0
    for i in range(first, last + 1):
        sum += const * i
    return sum

# first : is the first value of (n) (the index of summation)
# last : is the last value of (n)
# const : is the number that you want to sum its multiplication each (n) times with (n)

```
```
import numpy as np

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

```