Most modern mathematics might have summation in some parts of equation. Implementing this kind of equations in Python is very easy and straightforward. Python already provides built-in functions to help us, e.g., sum() and map().

For example, below is the expected information.

l(S) = -sum(Si/S * log2(Si/S))

map() helps us to compute each element one by one.

import math
 
def l(*s):
    S = float(sum(s))
    return -sum(map(lambda i: i/S*math.log(i/S,2),s))
 
print l(84,42)

As a result, we will get as follow.

0.918295834054

Tags: python, sum, map