python.py

import random


#returns either the same letter, or a random other, depending on mutation rate
def random_mutation(character, mutation_rate):
    if random.random() < mutation_rate:
        return random.choice('ABCDEFGHIJKLMNOPQRSTUVWXYZ ')
    return character

#take a parent string and make a child from it. How similar it is is dependent on mutation rate
def make_child(parent, mutation_rate):
    child = ""
    for character in parent:
        child = child + random_mutation(character, mutation_rate)
    return child


#decides how 'fit' the child is, how similar it is to the goal
def fitness(current, goal):
    return sum(current[i] == goal[i] for i in range(len(goal)))

#takes a parent and makes a number of childen, returns the fittest one
def make_best_child(parent, goal, mutation_rate, number_of_children):
    best_fitness = -1
    best_child = ""
    for child in range(0, number_of_children):
        current_child = make_child(parent, mutation_rate)
        current_fitness = fitness(current_child, goal)
        if best_fitness < current_fitness:
            best_child = current_child
            best_fitness = current_fitness
    return (best_child, best_fitness)

#sets the goal string, creates random start string, makes generations of children to find one that looks like the goal
def methinks(mutation_rate, number_of_children):
    goal = "METHINKS IT IS LIKE A WEASEL"
    goal_fitness = fitness(goal, goal)

    current = ""
    for i in range(0, len(goal)):
        current = current + random.choice('ABCDEFGHIJKLMNOPQRSTUVWXYZ ')
    current_fitness = fitness(current, goal)
    print(current)

    generation_count = 1
    while(goal_fitness != current_fitness):
        (current, current_fitness) = make_best_child(current, goal,
                mutation_rate, number_of_children)
        generation_count = generation_count + 1
        print(current)
    print("finished at generation")
    print(generation_count)



def main():
    mutation_rate = 0.04
    number_of_children = 100

    methinks(mutation_rate, number_of_children)

if __name__ == '__main__':
    main()