gtfs_import.py

    fd = Feed(local_gtfs_zip)

    try:
        fd.read_table('frequencies.txt')
    except (KeyError, IOError) as e:
        pass
    else:
        raise Exception('need to handle frequency based schedules')

    trips_by_route = defaultdict(list)
    for r in fd.read_table('trips.txt'):
        trips_by_route[r.route_id].append(r)

    stop_times_by_trip = defaultdict(list)
    for r in fd.read_table('stop_times.txt'):
        stop_times_by_trip[r.trip_id].append(r)

    calendar_exceptions = defaultdict(list)
    for r in fd.read_table('calendar_dates.txt'):
        calendar_exceptions[r.service_id].append(r)

    # etc.

    for route_row in fd.read_table('routes.txt'):
        route_id = route_row.route_id
        route_desc = route_row.route_short_name or route_row.route_long_name
        tables = []
        stops = set()
        for trip_row in trips_by_route[route_id]:
            stop_times = stop_times_by_trip[trip_row.trip_id]
            stop_ids = [st.stop_id for st in stop_times]
	    # now I store data in 'tables' similar to a timetable

Used with https://github.com/eoghanmurray/gtfs-sql/blob/master/gtfs/feed.py