def filter_by_population(min_pop):
    town_data = load_town_data()
    with open('sbb.csv', 'r') as stops, open('filtered.csv', 'w') as filtered:
        filtered.write("Name,Latitude,Longitude\n")
        for line in stops:
            values = line.split(';')  # Semikolon!
            name = values[0]
            try:
                lat = float(values[1])
                lng = float(values[2])
                if name in town_data:
                    if town_data[name]['population'] >= min_pop:
                        name = '"' + name + '"'  # Namen in "" einpacken
                        filtered.write(name + "," + str(lat) + "," + str(lng) + '\n')
            except ValueError:
                pass

filter_by_population(10000)