Programming Fundamentals › Object-Oriented Programming
Object-Oriented Programming
Organizing code around objects that bundle data and behavior.
Also known as: object-oriented, object oriented programming, OOP
Object-oriented programming (OOP) organizes code around objects that bundle data with the behavior that works on it, instead of keeping data and functions apart.
class Invoice:
def __init__(self, items):
self.items = items
def total(self):
return sum(i.price * i.qty for i in self.items)
def send(self, mailer):
mailer.send(self.total())The four ideas usually listed
| Idea | Meaning |
|---|---|
| Encapsulation | An object hides its internals and exposes a small interface |
| Abstraction | Use something by what it does, not how |
| Inheritance | One class extends another |
| Polymorphism | Different objects answer the same call in their own way |
Why it caught on
It matches how we describe many problems (a customer, an order), keeps related code together, and gives names to responsibilities. Big frameworks in Java, C#, Python and Ruby are built this way.
Honest trade-offs
- Inheritance gets overused. Deep hierarchies are rigid. Prefer combining small objects (composition over inheritance).
- Not everything is an object. Plain functions and data are simpler for many tasks, and languages like Python and JavaScript let you mix styles. Functional programming avoids shared mutable state altogether (functional programming).
- Anemic objects (only getters and setters, with all logic elsewhere) lose the benefit.
- Too many tiny classes can hide the logic across files.
Learn the ideas, but let the problem, not the paradigm, decide how to structure the code.