Simplify Negative Index

Sourcery refactoring id: simplify-negative-index

Description:

Replaces a[len(a)-1] with negative index lookup a[-1]

Before:

a = [1, 2, 3]
last_element = a[len(a) - 1]

After:

a = [1, 2, 3]
last_element = a[-1]

Explanation:

In Python you can access the end of a list by using negative indices. So my_list[-1] gets the final element, my_list[-2] gets the penultimate one and so on. Once you know the trick, reading code that uses it is much easier than the alternative.