Inheritance

• Project ImageShop is due today at 10:00pm
• Second midterm exam is this Friday 6th of November in this class!.
  • Exactly the same format as it was in Midterm 1 exam
  • Written in Canvas
  • Partially opened (Remember the definition of partially opened)
    • No programming in any development environment such as VS Code
    • You can look up your past assignments on GitHub or in your note but not from the VS code
    • You CANNOT Google or use any AI and/or any GenAI tools
  • Remember you MUST share your entire screen from the proctoring tool during exams
    • You are being watched!
• Focused on Chapters 4-6, and 8 (Graphics, Functions, Interactive Programs, and Lists)
  • Practice questions will be posted by tomorrow
  • No problem set this week: just studying for exam

• Inheritance lets a new class reuse and specialize the behavior of an existing class.
• The existing class is the parent (or base); the new class is the child (or subclass).
• A child gets the parent’s methods and attributes, and can add its own.

class Employee:
    def __init__(self, name):
        self.name = name

    def introduce(self):
        return f"Hi, I'm {self.name}."

class Manager(Employee):
    def approve_request(self):
        return f"{self.name} approved the request."

manager = Manager("Sam")
print(manager.introduce())
print(manager.approve_request())

• A subclass can define a method with the same name as a parent method.
• This is overriding: calling that method on a child uses the child’s version.

class Employee:
    def describe_role(self):
        return "I work at the company."

class Manager(Employee):
    def describe_role(self):
        return "I manage a team."

worker = Employee()
manager = Manager()
print(worker.describe_role())
print(manager.describe_role())

• super() gives a subclass access to methods from its parent class.
• Use super().__init__(...) to initialize the parent’s attributes instead of repeating that code.
• The child can then add its own attributes.

class Employee:
    def __init__(self, name):
        self.name = name

class Manager(Employee):
    def __init__(self, name, team_size):
        super().__init__(name)
        self.team_size = team_size

manager = Manager("Sam", 4)
print(manager.name, manager.team_size)

• An override can keep the parent’s behavior and build on it.
• Call super().method_name(...) from the child’s method.

class Employee:
    def describe_role(self):
        return f"{self.name} works at the company."

class Manager(Employee):
    def __init__(self, name, team_size):
        super().__init__(name)
        self.team_size = team_size

    def describe_role(self):
        description = super().describe_role()
        return f"{description} They lead {self.team_size} people."

manager = Manager("Sam", 4)
print(manager.describe_role())

• Start with a Pet class that stores a name and has a speak method.
• Create a Dog subclass that uses super() to initialize the name.
• Override speak so a dog says Woof!.
• Predict: What will print(dog.name, dog.speak()) display?

class Pet:
    def __init__(self, name):
        self.name = name

    def speak(self):
        return "..."

class Dog(Pet):
    def __init__(self, name):
        super().__init__(name)

    def speak(self):
        return "Woof!"

dog = Dog("Milo")
print(dog.name, dog.speak())