What Loop Can I Use To Iterate So That I Can Get The Following Output?

This is my code. def split_routes(routes_data): first_station = routes_data[0] #(’171’, ’1’, ’1’, ’59009’) curr_ser = first_station[1] #171 for entry in

Solution 1:

seems like your problem is that you use "first_station[1]" as a string and not use its value. try call filter_routes(routes_data,first_station[1]) and x = tuple([first_station[1]] + [a]) in addition, you use only your first station, I thing you meant to use ser value, and another problem is that you return and quit the function before you finish, store the values in variable like `resultz here, and return it when you finish:

result= []
for entry in routes_data:
        ser = entry[0]
        a = filter_routes(routes_data,ser) 
        x = tuple([ser] + [a])
        result.append(x) 
returnresult

However I would write it this way:

defsplit_routes(routes_filename):
    stations = {}
    withopen(routes_filename,"r") as routes_data:
        for line in routes_data:
            vals = line.strip().split(",") # [’171’, ’1’, ’1’, ’59009’]
            stations.setdefault(vals[0],[]).append(vals)
    result = []
    for st in stations:
        result.append((st,stations[st]))
    return result

and call it with the filename:

split_routes("bus_stations.txt")

Solution 2:

Here is one snippet that you can adapt for your use -

import fileinput

station_routes_map = {}

for line in fileinput.input():
    route = line.strip().split(',')
    first_station = route[0]
    if first_station not in station_routes_map:
        station_routes_map[first_station] = []

    station_routes_map[first_station].append(route)

output = [(key, value) for key, value in station_routes_map.items()]

This basically stores the output that you desire in the output variable. You can adapt it for your function. Might need a fix here and there, since I haven't tested it, but overall it should run.

UPDATE

Ok, let me explain. The file you have is in the format -

first_station, .....rest_of_the_route....

What you are looking for, is a list of tuples that have first station as the first param, followed by the list of all routes that begin with that first station.

What this code does is -

1. uses the fileinput module to read from your file, from command line (let's say)
2. splits the line on ',', and uses the first nibble as first_station
3. the station_routes_map dictionary is used to store the first_station as a key, and a list of routes as its value.
4. for every line, it figures out the first_station and then add the route to an appropriate list in the station_route_map (using first_station as the key)

After building the map, it just uses list-comprehension to prepare a list of tuples from the dictionary by iterating over all its items.