Ga in python

# Python3 program to create target string, starting from
# random string using Genetic Algorithm
 
import random
 
# Number of individuals in each generation
POPULATION_SIZE = 100
 
# Valid genes
GENES = '''abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOP
QRSTUVWXYZ 1234567890, .-;:_!"#%&/()=?@${[]}'''
 
# Target string to be generated
TARGET = "I love GeeksforGeeks"
 
class Individual(object):
    '''
    Class representing individual in population
    '''
    def __init__(self, chromosome):
        self.chromosome = chromosome
        self.fitness = self.cal_fitness()
 
    @classmethod
    def mutated_genes(self):
        '''
        create random genes for mutation
        '''
        global GENES
        gene = random.choice(GENES)
        return gene
 
    @classmethod
    def create_gnome(self):
        '''
        create chromosome or string of genes
        '''
        global TARGET
        gnome_len = len(TARGET)
        return [self.mutated_genes() for _ in range(gnome_len)]
 
    def mate(self, par2):
        '''
        Perform mating and produce new offspring
        '''
 
        # chromosome for offspring
        child_chromosome = []
        for gp1, gp2 in zip(self.chromosome, par2.chromosome):   
 
            # random probability 
            prob = random.random()
 
            # if prob is less than 0.45, insert gene
            # from parent 1
            if prob < 0.45:
                child_chromosome.append(gp1)
 
            # if prob is between 0.45 and 0.90, insert
            # gene from parent 2
            elif prob < 0.90:
                child_chromosome.append(gp2)
 
            # otherwise insert random gene(mutate),
            # for maintaining diversity
            else:
                child_chromosome.append(self.mutated_genes())
 
        # create new Individual(offspring) using
        # generated chromosome for offspring
        return Individual(child_chromosome)
 
    def cal_fitness(self):
        '''
        Calculate fittness score, it is the number of
        characters in string which differ from target
        string.
        '''
        global TARGET
        fitness = 0
        for gs, gt in zip(self.chromosome, TARGET):
            if gs != gt: fitness+= 1
        return fitness
 
# Driver code
def main():
    global POPULATION_SIZE
 
    #current generation
    generation = 1
 
    found = False
    population = []
 
    # create initial population
    for _ in range(POPULATION_SIZE):
                gnome = Individual.create_gnome()
                population.append(Individual(gnome))
 
    while not found:
 
        # sort the population in increasing order of fitness score
        population = sorted(population, key = lambda x:x.fitness)
 
        # if the individual having lowest fitness score ie.
        # 0 then we know that we have reached to the target
        # and break the loop
        if population[0].fitness <= 0:
            found = True
            break
 
        # Otherwise generate new offsprings for new generation
        new_generation = []
 
        # Perform Elitism, that mean 10% of fittest population
        # goes to the next generation
        s = int((10*POPULATION_SIZE)/100)
        new_generation.extend(population[:s])
 
        # From 50% of fittest population, Individuals
        # will mate to produce offspring
        s = int((90*POPULATION_SIZE)/100)
        for _ in range(s):
            parent1 = random.choice(population[:50])
            parent2 = random.choice(population[:50])
            child = parent1.mate(parent2)
            new_generation.append(child)
 
        population = new_generation
 
        print("Generation: {}\tString: {}\tFitness: {}".\
              format(generation,
              "".join(population[0].chromosome),
              population[0].fitness))
 
        generation += 1
 
     
    print("Generation: {}\tString: {}\tFitness: {}".\
          format(generation,
          "".join(population[0].chromosome),
          population[0].fitness))
 
if __name__ == '__main__':
    main()

-1

Source: geeksforgeeks.org

Similar codes

3 votes112 views1 answer
Djnagi import model form
Python
8 votes115 views2 answers
Discord python get member object by id
Python
0 vote105 views1 answer
Python how to request query string korean encode
Python
1 vote114 views1 answer
Polynomial regression using scikit-learn library
Python
1 vote108 views1 answer
Create empty numpy array without shape
Python
52 votes110 views2 answers
What is index in list in python
Python
45 votes101 views6 answers
How to increase the figure size in matplotlib
Python
0 vote107 views1 answer
Python declare variables from dictionary
Python
0 vote99 views1 answer
How to save string characters into char array or list in python
Python
5 votes130 views2 answers
Python string replace by index
Python