python classes and random number

I really don't understand what is going wrong so I'm going to try to outline everything. So I have this class called SortingNetwork which has def __init__(self):

It generates different random numbers every time it compiles

Then I have this in another file:

from sorting_network import SortingNetwork

POPULATION_SIZE = 20 #MUST BE DIVISIBLE BY 2

class Individual:
    def __init__(self):

        self.network = SortingNetwork()
        self.fitness = 0.0


class Population:

    def __init__(self):

        self.individuals = [Individual() for i in range(POPULATION_SIZE)]


    def evaluate(self):

        for i in range(0,POPULATION_SIZE):
            self.individuals[i].fitness=self.individuals[i].network.evaluate()

def run_genetic_algorithm():

    population = Population()
    population.evaluate()


    print(population)

Every individual has the same network and same fitness. Each time I run it though the network and fitness are different from before but all 20 are still the same network and fitness.