classes.py

"""
Classes and Objects Exercises - Complete the classes below
Run this file with: python topic.py
Or work interactively with: python3 -i topic.py
"""

from datetime import datetime

# Exercise 1: Basic Class Definition
class Person:
    """A class representing a person with name and age."""
    
    def __init__(self, name, age):
        """Initialize a person with name and age."""
        # Your code here
        pass
    
    def __str__(self):
        """Return string representation of the person."""
        # Your code here
        pass

# Exercise 2: Simple Methods (add to Person class above)
    def get_name(self):
        """Return the person's name."""
        # Your code here
        pass
    
    def get_age(self):
        """Return the person's age."""
        # Your code here
        pass
    
    def have_birthday(self):
        """Increase age by 1."""
        # Your code here
        pass
    
    def is_adult(self):
        """Return True if age >= 18."""
        # Your code here
        pass

# Exercise 3: Class with Behavior
class BankAccount:
    """A class representing a bank account."""
    
    def __init__(self, account_holder, initial_balance=0):
        """Initialize account with holder name and optional initial balance."""
        # Your code here
        pass
    
    def deposit(self, amount):
        """Add amount to the balance."""
        # Your code here
        pass
    
    def withdraw(self, amount):
        """Subtract amount from balance if sufficient funds."""
        # Your code here
        pass
    
    def get_balance(self):
        """Return current balance."""
        # Your code here
        pass
    
    def __str__(self):
        """Return string representation of the account."""
        # Your code here
        pass

# Exercise 4: Class with Validation
class Rectangle:
    """A class representing a rectangle with width and height."""
    
    def __init__(self, width, height):
        """Initialize rectangle with width and height (must be positive)."""
        # Your code here - include validation
        pass
    
    def get_area(self):
        """Calculate and return the area (width * height)."""
        # Your code here
        pass
    
    def get_perimeter(self):
        """Calculate and return the perimeter."""
        # Your code here
        pass
    
    def is_square(self):
        """Return True if width equals height."""
        # Your code here
        pass

# Exercise 5: Class with Lists
class ShoppingCart:
    """A class representing a shopping cart."""
    
    def __init__(self):
        """Initialize an empty shopping cart."""
        # Your code here
        pass
    
    def add_item(self, item, price):
        """Add an item with its price to the cart."""
        # Your code here
        pass
    
    def remove_item(self, item):
        """Remove an item from the cart."""
        # Your code here
        pass
    
    def get_total(self):
        """Calculate and return the total price of all items."""
        # Your code here
        pass
    
    def get_items(self):
        """Return a list of all items in the cart."""
        # Your code here
        pass
    
    def is_empty(self):
        """Return True if the cart is empty."""
        # Your code here
        pass

# Exercise 6: Class Relationships
class Student:
    """A class representing a student with grades."""
    
    def __init__(self, name, student_id):
        """Initialize student with name and ID."""
        # Your code here
        pass
    
    def add_grade(self, subject, grade):
        """Add a grade for a subject."""
        # Your code here
        pass
    
    def get_grade(self, subject):
        """Get the grade for a specific subject."""
        # Your code here
        pass
    
    def get_gpa(self):
        """Calculate and return the GPA (average of all grades)."""
        # Your code here
        pass
    
    def get_subjects(self):
        """Return a list of all subjects."""
        # Your code here
        pass

# Exercise 7: Class with Class Attributes
class Car:
    """A class representing a car with class-level counting."""
    
    total_cars = 0  # Class attribute to count all cars
    
    def __init__(self, make, model, year):
        """Initialize car with make, model, and year."""
        # Your code here - don't forget to increment total_cars
        pass
    
    def get_age(self):
        """Calculate and return the age of the car."""
        current_year = datetime.now().year
        # Your code here
        pass
    
    def __str__(self):
        """Return string representation of the car."""
        # Your code here
        pass
    
    @classmethod
    def get_total_cars(cls):
        """Return the total number of cars created."""
        # Your code here
        pass

# Exercise 8: Multiple Object Interaction
class Library:
    """A class representing a library with books."""
    
    def __init__(self):
        """Initialize empty library."""
        # Your code here
        pass
    
    def add_book(self, title, author):
        """Add a book to the library."""
        # Your code here
        pass
    
    def find_books_by_author(self, author):
        """Find all books by a specific author."""
        # Your code here
        pass
    
    def checkout_book(self, title):
        """Mark a book as checked out."""
        # Your code here
        pass
    
    def return_book(self, title):
        """Mark a book as available."""
        # Your code here
        pass
    
    def get_available_books(self):
        """Return list of available books."""
        # Your code here
        pass

# Exercise 9: Advanced Class Features
class Temperature:
    """A class representing temperature with multiple scales."""
    
    def __init__(self, celsius):
        """Initialize with temperature in Celsius."""
        # Your code here
        pass
    
    @property
    def celsius(self):
        """Get temperature in Celsius."""
        # Your code here
        pass
    
    @celsius.setter
    def celsius(self, value):
        """Set temperature in Celsius."""
        # Your code here
        pass
    
    @property
    def fahrenheit(self):
        """Get temperature in Fahrenheit."""
        # Your code here - convert from Celsius
        pass
    
    @fahrenheit.setter
    def fahrenheit(self, value):
        """Set temperature in Fahrenheit."""
        # Your code here - convert to Celsius
        pass
    
    @property
    def kelvin(self):
        """Get temperature in Kelvin."""
        # Your code here - convert from Celsius
        pass
    
    @kelvin.setter
    def kelvin(self, value):
        """Set temperature in Kelvin."""
        # Your code here - convert to Celsius
        pass
    
    def __str__(self):
        """Return string showing temperature in all scales."""
        # Your code here
        pass

def run_tests():
    """Test all the classes to verify they work correctly."""
    print("Testing Person class:")
    person = Person("Alice", 25)
    print(f"Person: {person}")                     # Should show Person(name=Alice, age=25)
    print(f"Name: {person.get_name()}")            # Should print Alice
    print(f"Is adult: {person.is_adult()}")        # Should print True
    person.have_birthday()
    print(f"After birthday: {person.get_age()}")   # Should print 26

    print("\nTesting BankAccount class:")
    account = BankAccount("Bob", 100)
    print(f"Account: {account}")                   # Should show account info
    account.deposit(50)
    print(f"After deposit: {account.get_balance()}")  # Should print 150
    account.withdraw(30)
    print(f"After withdrawal: {account.get_balance()}")  # Should print 120

    print("\nTesting Rectangle class:")
    rect = Rectangle(4, 5)
    print(f"Area: {rect.get_area()}")              # Should print 20
    print(f"Perimeter: {rect.get_perimeter()}")    # Should print 18
    print(f"Is square: {rect.is_square()}")        # Should print False
    
    square = Rectangle(4, 4)
    print(f"Square is square: {square.is_square()}")  # Should print True

    print("\nTesting ShoppingCart class:")
    cart = ShoppingCart()
    print(f"Empty cart: {cart.is_empty()}")        # Should print True
    cart.add_item("Apple", 1.50)
    cart.add_item("Banana", 0.75)
    print(f"Total: {cart.get_total()}")            # Should print 2.25
    print(f"Items: {cart.get_items()}")            # Should print ['Apple', 'Banana']

    print("\nTesting Student class:")
    student = Student("Charlie", "S123")
    student.add_grade("Math", 85)
    student.add_grade("Science", 92)
    print(f"Math grade: {student.get_grade('Math')}")  # Should print 85
    print(f"GPA: {student.get_gpa()}")            # Should print 88.5
    print(f"Subjects: {student.get_subjects()}")   # Should print ['Math', 'Science']

    print("\nTesting Car class:")
    print(f"Total cars before: {Car.get_total_cars()}")  # Should print 0
    car1 = Car("Toyota", "Camry", 2020)
    car2 = Car("Honda", "Civic", 2018)
    print(f"Car1: {car1}")
    print(f"Car1 age: {car1.get_age()}")          # Should print current year - 2020
    print(f"Total cars after: {Car.get_total_cars()}")  # Should print 2

    print("\nTesting Library class:")
    library = Library()
    library.add_book("1984", "George Orwell")
    library.add_book("Animal Farm", "George Orwell")
    library.add_book("To Kill a Mockingbird", "Harper Lee")
    
    orwell_books = library.find_books_by_author("George Orwell")
    print(f"Orwell books: {orwell_books}")        # Should print 2 books
    
    library.checkout_book("1984")
    available = library.get_available_books()
    print(f"Available books: {len(available)}")    # Should print 2

    print("\nTesting Temperature class:")
    temp = Temperature(0)  # 0 Celsius
    print(f"Temperature: {temp}")                  # Should show all three scales
    print(f"Fahrenheit: {temp.fahrenheit}")       # Should print 32.0
    print(f"Kelvin: {temp.kelvin}")               # Should print 273.15
    
    temp.fahrenheit = 100
    print(f"After setting to 100F: {temp.celsius}")  # Should print ~37.78

if __name__ == "__main__":
    print("Python Classes and Objects Exercises")
    print("=" * 50)
    print("Complete the classes above, then run this file to test them.")
    print("Uncomment the line below when you're ready to test:")
    print()
    # run_tests()  # Uncomment this line to run tests