Classes and Instances

Classes and Instances

In this lesson — part of Objects and Classes — you'll learn classes and instances in Python and why it matters in real work.

Why it matters

Classes bundle data and behavior together — the core of object-oriented design.

Key ideas

• Classes and instances
• Fields and methods
• Constructors
• Encapsulation

In practice

Here's how it looks in idiomatic Python:

class Dog:
    def __init__(self, name):  # constructor
        self.name = name       # instance field
    def bark(self):
        return f"{self.name} says woof"

d = Dog("Rex")
print(d.bark())

Python note: Methods take an explicit self as their first parameter, and __init__ is the initializer that sets up instance fields.

Try it yourself

Exercise: In Python, write a Bank Account class with deposit and withdraw methods.

Recap

You now understand classes and instances and can apply it in Python. Mark this lesson complete and continue to the next one.