Getting the Pareto Front for every generation

[diazguerra1103]

I am beginner using DEAP to run a multi objective optimization using eaMuPlusLambda. The following code returns the ParetoFront after the last generation. Is there any way to get a set of ParetoFront for each generation? I would like to see the evolution of the fronts with every generation.

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import random
import numpy
import matplotlib.pyplot as plt
from deap import base, creator, tools, algorithms

''' Objective Function 1 '''
def f1(individual):
x, y = individual
return x1 + y0

''' Objective Function 2 '''
def f2(individual):
x, y = individual
return (1+y)/x

def feasible(individual):
if 0.1 < individual[0] < 1:
if 0 < individual[1] < 5:
return True
return False

creator.create("FitnessMulti", base.Fitness, weights=(-1.0, -1.0))
creator.create("Individual", list, fitness=creator.FitnessMulti)

toolbox = base.Toolbox()
toolbox.register("attr_float", random.random)
toolbox.register("individual", tools.initRepeat, creator.Individual, toolbox.attr_float, n=2)
toolbox.register("population", tools.initRepeat, list, toolbox.individual)
toolbox.register("mate", tools.cxBlend, alpha=0.5)
toolbox.register("mutate", tools.mutGaussian, mu=0, sigma=1, indpb=0.2)
toolbox.register("evaluate", lambda ind: (f1(ind), f2(ind)))
toolbox.decorate("evaluate", tools.DeltaPenalty(feasible, 1000))
toolbox.register("select", tools.selNSGA2)

population = toolbox.population(n=100)

stats = tools.Statistics(lambda ind: ind.fitness.values)
stats.register('mean', numpy.mean, axis=0)
stats.register("min", numpy.min, axis=0)
stats.register("max", numpy.max, axis=0)

result, log = algorithms.eaMuPlusLambda(population, toolbox, mu=100, lambda_=200, cxpb=0.7, mutpb=0.2, ngen=200,
stats=stats,verbose=True)

pareto_front = tools.sortNondominated(population, len(population), first_front_only=True)[0]

O1 = []
O2 = []

for ind in pareto_front:
O1 = O1 + [ind.fitness.values[0]]
O2 = O2 + [ind.fitness.values[1]]

plt.scatter(O1, O2, label='Pareto Front’,s=10, marker=".", color='darkblue')
plt.show()