Related chapter: Object-Oriented Programming

Exercise 1: Bank Account

Create a BankAccount class with:

  • deposit(amount) — add to balance
  • withdraw(amount) — subtract if sufficient funds
  • balance property
  • Raise ValueError for invalid amounts or insufficient funds
  acc = BankAccount("Alice", 1000)
acc.deposit(500)
acc.withdraw(200)
print(acc.balance)  # 1300

Exercise 2: Rectangle and Square

Create a Rectangle class with width, height, area(), and perimeter(). Create a Square class that inherits from Rectangle.

  r = Rectangle(4, 5)
print(r.area())       # 20
s = Square(5)
print(s.area())       # 25

Exercise 3: Library System

Design classes for a simple library:

  • Book(title, author, isbn)
  • Member(name, member_id)
  • Library that can add_book, lend_book, return_book

Track which books are available vs lent out.

Exercise 4: Magic Methods

Create a Vector2D class with:

  • __init__(x, y)
  • __add__, __sub__, __mul__ (scalar)
  • __eq__, __str__, __repr__
  • magnitude() method
  v1 = Vector2D(3, 4)
v2 = Vector2D(1, 2)
print(v1 + v2)        # (4, 6)
print(v1.magnitude()) # 5.0

Exercise 5: Abstract Shape

Use ABC to create an abstract Shape class with area() and perimeter(). Implement Circle, Rectangle, and Triangle.

Challenge: Card Game

Create a Card and Deck class:

  • Deck has 52 cards, can shuffle() and deal(n)
  • Card has suit, rank, and __str__ (e.g., “Ace of Spades”)
  • Write a simple game function that deals two hands and compares sums
Solution (Exercise 1 sketch) 
  class BankAccount:
    def __init__(self, owner, balance=0):
        self.owner = owner
        self._balance = balance

    @property
    def balance(self):
        return self._balance

    def deposit(self, amount):
        if amount <= 0:
            raise ValueError("Amount must be positive")
        self._balance += amount

    def withdraw(self, amount):
        if amount <= 0:
            raise ValueError("Amount must be positive")
        if amount > self._balance:
            raise ValueError("Insufficient funds")
        self._balance -= amount

Exercise 6: Property Validation

Create a Person class where age must be between 0 and 150. Use @property and @age.setter to enforce this.

Exercise 7: Composition over Inheritance

Create Engine and Car classes. Car should contain an Engine (composition), not inherit from it. Car.start() delegates to Engine.start().

Next: Data Structures Exercises