Adding a loop to get result 'n' times and get the average into a csv - Python

I wrote a python function for particle filtering. I need to write a loop for the below function to save the best cost(Variable) for a csv file and get the average.

#loop should start here        
    pop_size=50
    #128 to #135 loop
    W = initial_population(region, scale , pop_size)

    pop = PatternPosePopulation(W, pat)
    pop.set_distance_image(imd)

    pop.temperature = 5

    Lw, Lc = pop.particle_filter_search(int(1000/pop_size),log=True)
    #Loop should end here for example run pop 50 x n times and store best_cost, take average of bestcost save to csv file.

    plt.plot(Lc)
    plt.title('Cost vs generation index')
    plt.show()

    print(pop.best_w)
    print(pop.best_cost)

Any help would be greatly appreciated.

best_costs = []
for iteration in range(n):     
    pop_size=50
    W = initial_population(region, scale , pop_size)

    pop = PatternPosePopulation(W, pat)
    pop.set_distance_image(imd)

    pop.temperature = 5

    Lw, Lc = pop.particle_filter_search(int(1000/pop_size),log=True)

    best_costs.append(pop.best_cost)#store the best cost for this iteration

    #Loop should end here for example run pop 50 x n times and store best_cost, take average of bestcost save to csv file.

    plt.plot(Lc)
    plt.title('Cost vs generation index')
    plt.show()

    print(pop.best_w)
    print(pop.best_cost)

#write to csv
best_cost_total = min(best_costs)
best_cost_avg = sum(best_costs) / n

results = [str(best_cost_total), str(best_cost_avg)]

with open('results.csv', 'w') as f:
    f.write(";".join(results))

This will write the best cost and the average to results.csv with ; as delimiter. For a more specific approach, more information would be needed...

Edit: You're right, the writing to csv part should be after the loop