2.5. Hierarchical Inheritance

A parent class can have any number of child classes, which allows us to create a class hierarchy.

The syntax for this remains the same as before

class ParentClassName:

    def __init__(self, parameter_1, ..., parameter_n):
        # Set values here

class ChildClassName1(ParentClassName):

    def __init__(self, parameter_1, ..., parameter_n):
        # Set values here

class ChildClassName2(ParentClassName):

    def __init__(self, parameter_1, ..., parameter_n):
        # Set values here

Example

In the example below the SavingsAccount and FeeChargingAccount classes inherit from the BaseAccount

class BaseAccount:

    def __init__(self, bsb_number, account_number, balance, holder_name):
        self.bsb_number = bsb_number
        self.account_number = account_number
        self.balance = balance
        self.holder_name = holder_name

    def deposit(self, amount):
        self.balance += amount

    def withdraw(self, amount):
        self.balance -= amount

class SavingsAccount(BaseAccount):

    def __init__(self, bsb_number, account_number, balance, holder_name, interest_rate):
        super().__init__(bsb_number, account_number, balance, holder_name)
        self.interest_rate = interest_rate

class FeeChargingAccount(BaseAccount):

    def withdraw(self, amount):
        fee = 2.50
        super().withdraw(amount + fee)  # Calls the method defined on line 8

Code Challenge: Infinite Cargo Ship

Thanks to advancements in quantum technology we can now store an infinite amount of a single type of bulk cargo in spaceships. You’ve decided to add these special ships to your fleet.

Add a child class of Spaceship called InfiniteCargoShip that is used to transport a potentially infinite amount of bulk cargo. The InfiniteCargoShip has:

• an attribute cargo_volume initialised to 0 which tracks how much bulk cargo is on board

• a load_cargo method which accepts volume parameter and increases the cargo volume

• an unload_cargo method which reduces the volume by a given amount down to zero. this method returns how much volume was actually unloaded.

InfiniteCargoShip Specifications

• Inherit from the provided Spaceship class

• Additional attributes:

  • cargo_volume as described above

• __init__ method with

  • Parameters:

    • self

    • name

    • fuel_capacity

  • Actions:

    • Call the Spaceship constructor to set common attributes with the same name

    • Set the cargo_volume attribute to 0

• load_cargo method with

  • Parameters

    • self

    • volume

  • Actions

    • Increase the cargo_volume by the given volume

• unload_cargo method with

  • Parameters

    • self

    • volume

  • Actions

    • Reduce the cargo_volume by the given volume down to 0.

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


# ADD YOUR CLASS HERE


freighter = InfiniteCargoShip("Galactic Freighter", fuel_capacity=800)

freighter.load_cargo(200)

freighter.unload_cargo(150)
print(freighter.cargo_volume)

unloaded_volume = freighter.unload_cargo(100)
print(unloaded_volume)

print(freighter.cargo_volume)

Solution

Solution is locked