Python Class Exercises: Build a Small Object Model

Start with a blueprint

A class groups data and behaviour. __init__ runs when an object is created and assigns the initial attributes. Keep the first version small: two fields are enough to see the pattern.

class Order:
    def __init__(self, drink, price):
        self.drink = drink
        self.price = price

order = Order("latte", 4.5)
print(order.drink, order.price)

A two-field class

Add a method

A method is a function inside the class. Its first parameter is self, which refers to the current object. Call the method on an instance; do not pass self yourself.

class Order:
    def __init__(self, drink, price, quantity=1):
        self.drink = drink
        self.price = price
        self.quantity = quantity

    def total(self):
        return self.price * self.quantity

print(Order("latte", 4.5, 2).total())

A computed total

Keep instances independent

Each object has its own attributes. Creating a second Order does not overwrite the first. Put the objects in a list when you need to process several records with the same loop.

class Order:
    def __init__(self, drink, price):
        self.drink = drink
        self.price = price

orders = [Order("latte", 4.5), Order("tea", 3.0)]
for order in orders:
    print(order.drink, order.price)

Several independent objects

Use a method for a repeated calculation

If every caller would otherwise repeat the same formula, move it into a method. The method name documents the intent, and the calculation has one place to change.

class Order:
    def __init__(self, price, quantity):
        self.price = price
        self.quantity = quantity

    def total(self):
        return self.price * self.quantity

print(Order(4.5, 3).total())

One place for the formula

Know when a dictionary is enough

A class is not mandatory. If you only need to pass a fixed record around, a dictionary may be simpler. Introduce a class when behaviour and state belong together, or when the same operations keep repeating.

order = {"drink": "latte", "price": 4.5}
print(order["drink"])
print(order["price"] * 2)

A dictionary alternative

Your practice checklist

• Define __init__ with self as the first parameter.
• Assign attributes with self.name = value.
• Call methods on an instance, not on the class.
• Start with one small class before adding inheritance.

Common questions

Keep reading:

• Python Classes and Objects
• Python Practice for Beginners: A Simple 4-Week Plan
• Python Exercises With Answers: How to Practice Without Copying