Object-Oriented Programming in Python — classes, inheritance, polymorphism, encapsulation, abstract classes, and design patterns.
Encapsulation (bundling data + methods), Abstraction (hiding complexity), Inheritance (reusing code from parent), Polymorphism (same interface, different behavior).
💡 Memory Trick: "A PIE — Abstraction, Polymorphism, Inheritance, Encapsulation"
__new__ creates the instance (allocates memory), __init__ initializes it (sets attributes). __new__ is called first.
class Singleton:
_instance = None
def __new__(cls):
if cls._instance is None:
cls._instance = super().__new__(cls)
return cls._instance
def __init__(self):
self.value = 42💡 Memory Trick: "__new__ = Builder (creates house) | __init__ = Interior Designer (furnishes it)"
MRO determines the order in which base classes are searched when calling a method. Python uses the C3 Linearization algorithm. Check with ClassName.__mro__ or ClassName.mro().
class A: pass
class B(A): pass
class C(A): pass
class D(B, C): pass
print(D.__mro__)
# (D, B, C, A, object)💡 Memory Trick: "MRO = Left to Right, Depth Last (C3 linearization)"
@staticmethod doesn't receive cls or self — it's a regular function in a class namespace. @classmethod receives the class (cls) as first argument and can access/modify class state.
class Model:
version = "1.0"
@classmethod
def get_version(cls):
return cls.version # Access class attribute
@staticmethod
def validate_input(x):
return x > 0 # No access to class/instance💡 Memory Trick: "classmethod = knows its CLASS | staticmethod = STANDALONE utility"
Questions 55-100 continue with the same detailed format.
Topics covered: Abstract Base Classes, Property Decorators, Dunder Methods (__str__, __repr__, __eq__), Descriptors, Slots, Mixins, Multiple Inheritance Diamond Problem, Composition vs Inheritance, Design Patterns (Singleton, Factory, Observer), Dataclasses, and more.
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