Weasel program redux

weasel_redux.py

import string, random

CHARS = string.uppercase + ' '
PROGENY = 100
RATE = 0.05
TARGET = 'METHINKS IT IS LIKE A WEASEL'

genotype = lambda s : [random.choice(s) for x in xrange(len(TARGET))]
phenotype = ''

def fitness(phenotype):
    return sum([x == y for x,y in zip(phenotype, TARGET)])

def mutate(phenotype):
    return [(random.choice(CHARS) if random.random() < RATE else c) for c in phenotype]

phenotypes = [''.join(genotype(CHARS)) for x in xrange(PROGENY)]
population = [''.join(mutate(l)) for l in phenotypes]

i = 0
while phenotype != TARGET:
    
    points = []
    for phenotype in population:
        score = fitness(phenotype)
        points.append(score)
        
    winner = max(points)
    phenotype = population[points.index(winner)]
    population = [''.join(mutate(phenotype)) for x in xrange(PROGENY)] 
    
    print('{0}: {1} -- score: {2}'.format(i, phenotype, winner))
    
    i += 1