Genetic Hello World

ga_hello.py

import random, string
from operator import attrgetter

max_iters       = 1024
start_pop       = 4096
mutate_chance   = .25
elite_chance    = .10 # keep the top
elite      = int(start_pop*elite_chance)
goal            = "Hello, World!"
goal_len        = len(goal)
options         = string.letters
options += " !@#$%^&*()"

class Citizen:
    def __init__(self, body):
        self.fitness = citizen_fitness(body)
        self.body = body

    def __repr__(self):
        return self.body + " => " + str(self.fitness)

def mate(pop):
    new_pop = pop[:elite]
    for i in range(elite, start_pop):
        rand1 = int((random.random() * 1000) % elite)
        rand2 = int((random.random() * 1000) % elite)
        rand_pos = int((random.random() * 100) % goal_len)
        new_body = pop[rand1].body[:rand_pos] + pop[rand2].body[rand_pos:]

        if random.random() < mutate_chance:
            new_body = mutate(new_body)

        new_pop.append(Citizen(new_body))
    return new_pop

def mutate(body):
    pos = int((random.random()*1000) % goal_len)
    char = chr((ord(body[pos]) + int((random.random() * 200))) % 122)
    return body[:pos] + char + body[pos+1:]
    

def calc_fitness(str):
    for p in pop:
        p.fitness = citizen_fitness(p.body)
    return pop

def citizen_fitness(str):
    fitness = 0
    for i in range(goal_len):
        fitness += abs(ord(str[i]) - ord(goal[i]))
    return fitness

def init_pop():
    population = []

    for i in range(start_pop):
        body = ""
        for j in range(goal_len):
            body += random.choice(options)
        citizen = Citizen(body)
        population.append(citizen)

    return population

if __name__ == '__main__':
    pop = init_pop()
    for i in range(max_iters):
        pop = sorted(pop, key=attrgetter('fitness'))
        print str(i) + ") " + str(pop[0]) # top performer

        if pop[0].fitness == 0:
            break

        pop = mate(pop)
        #print pop