Tournament Selection on Python

Question

How do you implement a Roulette wheel Selection on python so that it shows half of the total population after execution?

So first I generated a total of 100 random words and specified a certain letter to be counted at the beginning of each word. Afterwards, I am expected to halve the total population(100 words to 50 words) using roulette wheel selection. How do I implement roulette wheel selection using the following code?

import random
import numpy as np

def population (length, amount, letter, selection):
    alfa='abcdefghijklmnñopqrstuvwxyz'
    item=[]
    fitness=0
    fitness_it=0
    individual=[]
    individual2=[]
    for i in range (amount):
        words =''.join(random.choices(alfa, k=length))
        aptitude = str(words.count(letter))
        item.append(aptitude + words)
        item = [x.upper() for x in item]
        item.sort(reverse=True)
        fitness = fitness + int(aptitude)
    fitness = fitness/amount
    maxi = item[0]
    print(np.array(item))
    print(maxi[0],round(fitness,2))