Inheritance #

In this lab you will learn inheritance and create an OOP representation of an Event Management system.

Syllabus Topics [HL] #

• B3.2.1 Explain and apply the concept of inheritance in OOP to promote code reusability.

Key Vocabulary #

Simple Inheritance Example #

Here is a simple example of a Superclass and a Subclass. Be sure to notice how super() is used in the Dog constructor and in speak().

class Animal:                           # Define Superclass
    def __init__(self, name):
        self.__name = name

    def speak(self):
        print(f"{self.__name} says hi!")

class Cat(Animal):                              # Define Subclass
    def __init__(self, name, color):
        self.__name = name
        self.__color = color

class Dog(Animal):                      # Define Subclass
    def __init__(self, name, breed):
        super().__init__(name)          # Invoke superclass's constructor

        self.__breed = breed

    def speak(self):
        super().speak()                 # Invoke the Superclass's speak method
        print("*bark bark*")             # Extends functionality


#####


a = Animal('Ringo')
a.speak()                               # "Ringo says hi!"
isinstance(a, Animal)                   # Returns True

c = Cat('George')
c.speak()                               # "George says hi!"
isinstance(c, Cat)                      # Returns True
isinstance(c, Dog)                      # Returns False
isinstance(d, Animal)                   # Returns True

d = Dog('Starr', 'Poodle')
d.speak()                               # "Starr says hi! *bark bark*"
isinstance(d, Dog)                      # Returns True
isinstance(d, Animal)                   # Returns True

[0] Class Relationships #

In this lab, you will implement multiple classes for a Event Management System.

• Event()
• Concert()
• Sport()
• Wedding()
• ManagementSystem()

📖 Here is the UML diagram for the class relationships.

• The empty arrows represents an inheritance relationship
• The filled diamond represents a aggregation relationship

classDiagram
    class Event {
        - name: str
        - date: str
        - num_attendees: int
        - max_attendees: int
        + \_\_init__(name, date, max_attendees)
        + get_name()
        + get_date()
        + get_num_attendees()
        + get_max_attendees()
        + register_attendee()
        + \_\_str__()
    }

    class Concert {
        - artist: str
        - num_vips : int
        + \_\_init__(name, date, max_attendees, artist)
        + \_\_str__()
        + get_artist()
        + get_num_vips()
        + register_attendee(is_vip)
    }

    class Sport {
        + seat_number: int$
        - sport: str
        - home_team: str
        - away_team: str
        + \_\_init__(name, date, max_attendees, sport, home_team, away_team)
        + \_\_str__()
        + register_attendee(): int
    }

    class Wedding {
        - venue: str
        - num_vegetarians: int
        - num_omnivores: int
        + \_\_init__(name, date, max_attendees, venue)
        + \_\_str__()
        + get_venue()
        + register_attendee(diet)
    }

    class ManagementSystem{
        - events: list
        + schedule_event(Event)
        + register_attendee(event_name, attendee_name, attendee_email)
        + display_events(event_type: Event = None)
    }

   
    Event <|-- Concert: is a
    Event <|-- Sport: is a
    Event <|-- Wedding: is a
    Event --* ManagementSystem: part of

[1] Set up #

💻 Clone your repo in the correct folder. Be sure to replace yourgithubusername with your actual username.

cd ~/desktop/dpcs/unit03_oop
git clone https://github.com/isf-dp-cs/lab_inheritance_yourgithubusername

cd lab_inheritance_yourgithubusername

💻 Enter the Poetry Shell to start the lab. As a reminder, we will run this command at the start of each lab, but only when we are inside a lab folder.

poetry shell

👾 💬 Exiting the poetry shell

When you want to exit the shell, you can type exit or ^D

[2] Test the Superclass and a Subclass #

💻 Test the Event superclass.

💻 Test the Concert subclass.

• understand how super() works.
• test the superclass methods on a Concert object

[3] Implement the UML #

💻 Only parts of the UML diagram are constructed. It is up to you to construct the following classes. Refer to the full UML diagram in Class Relationships to ensure it is implemented as planned.

1️⃣ Sport(Event)

• register_attendee() - should return the seat_number and increase the static variable seat_number

classDiagram

    class Sport {
        + seat_number: int$
        - sport: str
        - home_team: str
        - away_team: str
        + \_\_init__(name, date, max_attendees, sport, home_team, away_team)
        + \_\_str__()
        + register_attendee(): int
    }

2️⃣ Wedding(Event)

• register_attendee() - should increase num_vegetarians or num_omnivores based on its parameter diet

classDiagram
    class Wedding {
        - venue: str
        - num_vegetarians: int
        - num_omnivores: int
        + \_\_init__(name, date, max_attendees, venue)
        + \_\_str__()
        + get_venue()
        + register_attendee(diet)
    }
   

3️⃣ EventManagementSystem

classDiagram
    class ManagementSystem{
        - events: list
        + schedule_event(Event)
        + register_attendee(event_name, attendee_name, attendee_email)
        + display_events(event_type: Event = None)
    }

[4] Deliverables #

⚡✨ Once you finish the lab, be sure to complete these two steps:

📋 Update Syllabus Checklist: Go to your Syllabus Content Checklist in your Google Drive and update it accordingly.

💻 Push your work to Github

• git status
• git add -A
• git status
• git commit -m “describe your code here”
• git push
• remote