Step 1: Thought Process / Set up
Step: 2: Function Set Up
def triplet(array, sum); array.sort() three_sum =  for : if elif return three_sum
Here is the basic outline of the problem we will solve. We define a function with parameters of an array and sum. I use the basic sorting method to sort the array. I set up an empty list that we will add our three number sum to.
Now that I have the skeleton of the problem, we can start filling out the rest.
for i in range(len(array)-2):
Because we are looking for a three number sum, we will loop through the array and stop before the last two elements.