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Python Classes & Object-Oriented Programming
Object-oriented programming in Python: classes, __init__, self, methods, and inheritance.
📋 Copy Python OOP Class & Dataclass Pattern Snippet
from dataclasses import dataclass, field
from typing import List
# Modern Python Dataclass (Python 3.7+)
@dataclass
class Player:
username: str
level: int = 1
inventory: List[str] = field(default_factory=list)
def gain_xp(self, xp: int) -> None:
self.level += xp // 100
@property
def is_veteran(self) -> bool:
return self.level >= 50
steve = Player("Steve", level=10)Interactive Sandbox & Core Concepts
Python is celebrated for its clean syntax, high readability, and expressive standard library. Understanding Python Classes & Object-Oriented Programming is essential for backend engineering, high-throughput automation, and data pipelines.
⚠️ 5 Fatal Traps & Python Pitfalls
Trap #1: Class Attribute vs. Instance Attribute Mutation
Defining a mutable list directly inside the class body (
class Team: members = []) shares that list across ALL instances! Always initialize mutable attributes inside __init__ on self.Trap #2: Forgetting self in Instance Method Signatures
Defining
def attack(): inside a class fails with TypeError: attack() takes 0 positional arguments but 1 was given because Python automatically passes the instance as the first argument.Trap #3: Dataclass Mutable Default Value Error
Writing
items: list = [] inside a @dataclass raises a ValueError: mutable default is not allowed. Use field(default_factory=list) instead.Trap #4: Assuming Double Underscore __var Makes Fields Private
Python does not have true private variables. Double underscores trigger name mangling (renaming to
_ClassName__var), but it can still be accessed and modified externally.Trap #5: Diamond Problem & Inconsistent super() Calls
Failing to use
super().__init__() in multiple inheritance disrupts Python's Method Resolution Order (MRO), causing parent initialization methods to be skipped.💬 Frequently Asked Questions
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