solution.py

INDEX, INS_DATE, ORIGIN, DEST, DEP_DATE = 0, 1, 2, 3, 4
ARR_DATE, TR_TYPE, PRICE, TR_CLASS, FARE = 5, 6, 7, 8, 9


def load_csv(filename):
    with open(filename, 'r') as file:
        head = tuple(next(file).strip().split(','))
        data = []
        for line in file:
            row = tuple(line.strip().split(','))
            data.append(row)
    data.sort(key=lambda row: row[DEP_DATE])
    return head, data


def splitby_origin_dest(data):
    datas_origin_dest = {}
    for row in data:
        origin_dest = row[ORIGIN].lower() + '-' + row[DEST].lower()
        if origin_dest in datas_origin_dest:
            datas_origin_dest[origin_dest].append(row)
        else:
            datas_origin_dest[origin_dest] = []
    return datas_origin_dest


def save_csvs(head, datas):
    for filename, data in datas.items():
        with open(filename + '.csv', 'w') as file:
            file.write(','.join(head) + '\n')
            for row in data:
                file.write(','.join(row) + '\n')


def interactive_mode(datas_origin_dest):
    while True:
        origin = input('Enter origin: ')
        if not origin:
            return
        dest = input('Enter destination: ')
        origin_dest = origin.lower() + '-' + dest.lower()
        if origin_dest in datas_origin_dest:
            data = datas_origin_dest[origin_dest]
            date = input('Enter departure date as YYYY-MM-DD: ')
            if len(date) == 10:
                trains = list(filter(lambda row: row[DEP_DATE].startswith(date), data))
                if len(trains):
                    trains.sort(key=lambda row: float(row[PRICE]))
                    print(f'Listing the trains from {origin} to {dest} on {date}:')
                    for row in trains:
                        print(row[ORIGIN:])
                else:
                    print(f'No such trains')
            else:
                print('Wrong date format')
        else:
            print('No such combination of cities')


head, data = load_csv('renfe.csv')
datas_origin_dest = splitby_origin_dest(data)
save_csvs(head, datas_origin_dest)
interactive_mode(datas_origin_dest)