Object-Oriented Programming is a paradigm that organizes software design around objects rather than functions and logic, bundling data with methods that operate on that data. It emerged in the 1960s and became mainstream through languages like Smalltalk, C++, Java, and Python, fundamentally changing how developers structure reusable, maintainable code. At its core, OOP is built on four foundational pillars—encapsulation, inheritance, polymorphism, and abstraction—that together enable modeling real-world problems as interacting objects. Understanding when to favor composition over inheritance, how generics provide type-safe reuse, and recognizing common anti-patterns like God Objects are crucial for writing clean, scalable object-oriented systems.
What This Cheat Sheet Covers
This topic spans 21 focused tables and 151 indexed concepts. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.
Table 1: Core Concepts
| Concept | Example | Description |
|---|---|---|
class Dog: def __init__(self, name): self.name = name | • Blueprint or template that defines structure and behavior for objects • contains attributes (data) and methods (functions). | |
my_dog = Dog("Rex")my_dog.name | • Concrete realization of a class • an individual entity with its own state created from the class blueprint. | |
class Account: def __init__(self): self.__balance = 0 | Bundling data and methods into a single unit (class) while hiding internal implementation details from outside access. | |
class Puppy(Dog): def __init__(self, name, age): super().__init__(name) | • Mechanism where a class derives properties and behavior from another class • creates "is-a" relationships (e.g., Puppy is a Dog). | |
def make_sound(animal): animal.speak() | • Ability for objects of different types to respond to the same method call • enables treating related objects uniformly through a common interface. |