Python Basics: Object Oriented Programming (OOP)

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OOP Cheat Sheet (Extra)

Lesson 7 of 7 • 10 XP

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🐍 Python OOP Cheat Sheet

A quick reference for everything you’ve learned in the Python Basics: Object-Oriented Programming quest.

1. Classes and Objects

Defining a Class

class Person:
    def __init__(self, name, age):
        self.name = name      # Public attribute
        self.age = age        # Public attribute

    def greet(self):
        print(f"Hello, my name is {self.name} and I am {self.age} years old.")
````

**Creating an Object**

```python
p1 = Person("John", 30)
p1.greet()   # Hello, my name is John and I am 30 years old.

2. Attributes and Methods

  • Attributes = variables that belong to an object (self.attribute)
  • Methods = functions that belong to an object (def method(self):)

Accessing:

print(p1.name)   # Attribute
p1.greet()       # Method

3. Inheritance

Basic Inheritance

class Animal:
    def __init__(self, name):
        self.name = name

    def sound(self):
        print("Some generic sound")

class Dog(Animal):
    def sound(self):
        print("Woof woof!")

dog = Dog("Rex")
dog.sound()  # Woof woof!

4. super()

Calling Parent’s Constructor

class Dog(Animal):
    def __init__(self, name, breed):
        super().__init__(name)   # Call Animal's __init__
        self.breed = breed

5. Method Overriding

Child classes can replace parent methods:

class Cat(Animal):
    def sound(self):
        print("Meow!")

6. Private Attributes & Methods

Mark as Private with __

class Person:
    def __init__(self, name, age):
        self.name = name
        self.__age = age  # Private attribute

    def __print_age(self):  # Private method
        print(self.__age)

    def show_info(self):
        print(self.name)
        self.__print_age()

Accessing private members directly will fail:

p = Person("Alice", 25)
p.__age         # ❌ AttributeError
p._Person__age  # ✅ Works, but not recommended

7. Key OOP Terms

Term Meaning
Class Blueprint for objects.
Object Instance of a class with its own data.
Attribute Variable inside an object.
Method Function inside a class.
Constructor Special method __init__ called when creating an object.
Inheritance Mechanism for reusing code from another class.
Overriding Redefining a method from a parent class.
super() Calls methods from the parent class.
Private Prefixed with __ to indicate internal use only.

8. Quick Best Practices

  • Use PascalCase for class names: MyClass
  • Use self to refer to the current object
  • Keep methods focused on one task
  • Use private members for internal details
  • Call super().__init__() if you override __init__ in a child class
  • Prefer composition or inheritance wisely — don’t inherit just for the sake of it

📌 Remember: OOP is about thinking in nouns (things) and their behaviors. Model real-world concepts, keep code organized, and reuse where possible.