3.4. Extension: Container Methods

These allow custom objects to behave like collections or sequences (e.g. lists, dicts).

3.4.1. __getitem__

Used when you access an item by index or key (obj[key]).

def __getitem__(self, index):
    return self.cargo[index]

3.4.2. __iter__

Allow iteration using for item in obj.

def __iter__(self):
    return iter(self.cargo)

Code Challenge: CargoShip Items

Note

The intergalactic parliament is now upping the customs screen and demands to look at every item on board.

Complete the CargoShip class with __getitem__ and __iter__ and methods to enable use of ship[idx] and for item in ship.

Requirements

• __getitem__ must return the item at the given index

• __iter__ must return an iterable over the cargo items in the normal order

Note

You can return Python’s built in iter on the cargo items

Example

>>> freighter = CargoShip("Galactic Freighter", fuel_capacity=10000)
>>> freighter.refuel(1000)
>>> freighter.load("Turbo Encabulator")
>>> freighter.load("Phase Dectractor")
>>> freighter.load("Cardinal Grammeter")
>>> print(freighter[1])
Phase Dectractor

>>> for item in freighter:
...    print(item)
Turbo Encabulator
Phase Dectractor
Cardinal Grammeter

Here is some code for you to start with:

class Spaceship:
    def __init__(self, name, fuel_capacity):
        self.name = name
        self.fuel_weight = 0
        self.fuel_capacity = fuel_capacity

    def refuel(self, weight):
        if self.fuel_weight + weight > self.fuel_capacity:
            self.fuel_weight = self.fuel_capacity
        else:
            self.fuel_weight += weight

    def fire_laser(self):
        if self.fuel_weight >= 10:
            self.fuel_weight -= 10

    # YOUR METHODS HERE



class CargoShip(Spaceship):
    def __init__(self, name, fuel_capacity):
        super().__init__(name, fuel_capacity)
        self.cargo = []

    def load(self, item):
        self.cargo.append(item)

    def unload(self):
        if self.cargo:
            return self.cargo.pop()
        return None

    # YOUR METHODS HERE



freighter = CargoShip("Galactic Freighter", fuel_capacity=10000)
freighter.refuel(1000)

freighter.load("Turbo Encabulator")
freighter.load("Phase Dectractor")
freighter.load("Cardinal Grammeter")

print(len(freighter))

print(freighter)

Solution

Solution is locked