Question

I have a fairly basic question regarding python lists/dictionaries which I would like some help on.

I have some data relating to electric vehicles which have different characteristics. Each EV has an:

• ID e.g. 12345
• A battery size e.g. 24
• A state of charge for each five minute period of the day e.g. 00:05:00 : 1; 00:10:00 : 0.95

How best do I go about this? I had been trying various combinations of lists/dicts but can’t quite get it to work. I’d like to be able to access the data by e.g.:

EV['ID'][2]['Batt']['SOC'][5] which would return e.g. 0.95 or
EV[12345]['Batt']['SOC'][5]

My latest attempt was:

EV = defaultdict(lambda: defaultdict(dict))

EV['ID']['Batt']['Time']=[]
EV['ID']['Batt']['SOC']=[]
EV['ID']['Batt']['Size'] = 24

However this didn’t allow for the entry of multiple IDs which are in another list admin[‘ID’]. It yielded:

{'ID': defaultdict....,{'Batt':{'SOC:[], 'Size':24, 'Time':[]}}}}

I would appreciate your help!

Answer 1

from collections import defaultdict
import datetime

class ElectricVehicle(object):
    ev_by_id = {}
    ev_by_battery = defaultdict(list)

    @classmethod
    def find(cls, id=None, battery=None):
        if id is not None:
            return [cls.ev_by_id[id]]
        elif battery is not None:
            return cls.ev_by_battery[battery]
        else:
            return []

    def __init__(self, id, battery, states):
        self.id = id
        ElectricVehicle.ev_by_id[id] = self

        self.battery = battery
        ElectricVehicle.ev_by_battery[battery].append(self)

        self.states = list(states)

    def state_at(self, time):
        return self.states[(time.hour*60 + time.minute)/5]

ElectricVehicle(12345, 24, [0.99, 0.99, 0.99])
ElectricVehicle(12346, 30, [0.90, 0.90, 0.89])

evs = ElectricVehicle.find(battery=24)
for ev in evs:
    time = datetime.time(0,3,0)    # 00:03:00
    print("{}: {}".format(ev.id, ev.state_at(time)))

# will print "12345: 0.99"