Roulette wheel selection example in python for minimisation problems

roulette_wheel_selection_minimization.py

import numpy as np

def roulette_wheel_selection(population):
  
    # Computes the totallity of the population fitness
    population_fitness = sum([chromosome.fitness for chromosome in population])
    
    # Computes for each chromosome the probability 
    chromosome_probabilities = [chromosome.fitness/population_fitness for chromosome in population]
    
    # Making the probabilities for a minimization problem
    chromosome_probabilities = 1 - np.array(chromosome_probabilities)
    
    # Selects one chromosome based on the computed probabilities
    return np.random.choice(population p=chromosome_probabilities)

This function is throwing errors for me. chromosome.fitness.values[0] in place of chromosome.fitness is working.

Also, sum of probabilities is not one. Hence, this is not working.

Maybe you would be interested in checking the full code and adapt it to yours.
https://github.com/rocreguant/personal_blog/tree/main/Genetic_Algorithm_Python_Example
If you have more questions I'm glad to answer them ;)