Create multiple lists that meet one condition Python 3.6 -

i have class city:

class city(object):     #a city has 2 coordinates in graph(x,y), , set of order     def __init__(self, name, x, y, orders):         self.name = name         self.x = x         self.y = y         self.orders = orders 

i create list of cities:

example:

list_cities = [city1, city2, city3, city4]  city1 (0.0, 0.0) [1, 2] city2 (1.0, 0.0) [2, 3] city3 (2.0, 0.0) [1, 3] city4 (3.0, 0.0) [2] 

i group cities orders this:

list1 = [city1, city3] list2 = [city1, city2, city4] list3 = [city2, city3] 

i've tried dictionaries, list lists , sets still not give me results , not know how else it. leave code have tried:

tours = [] city = city.create(arraycity)  in range(0,len(city.orders)):     tours[city.orders[i]].append(city) 

this outputs:

indexerror: list index out of range 

i hope can me. thank much

class city:     def __init__(self,name,x,y,orders):         self.name = name         self.x = x         self.y = y         self.orders = orders  city1 = city('city1',0.0,0.0,[1,2]) city2 = city('city2',1.0,0.0,[2,3]) city3 = city('city3',2.0,0.0,[1,3]) city4 = city('city4',3.0,0.0,[2])  list_cities = [city1, city2, city3, city4]  group_cities_by_orders = {}  in range(1,len(list_cities)+1):     city in list_cities:         if in city.orders:             if in group_cities_by_orders:                 group_cities_by_orders[i].append(city.name)             else:                 group_cities_by_orders[i] = [city.name]    print(group_cities_by_orders)  output: {1: ['city1', 'city3'], 2: ['city1', 'city2', 'city4'], 3: ['city2', 'city3']}