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How to Implement the Repository Pattern in Python with an In-Memory Dict
Stores, retrieves, updates, and deletes user records in memory using a Repository abstraction over a plain dict, isolating data access from business logic.
class UserRepository:
def __init__(self):
self._storage = {}
self._next_id = 1
def create(self, name, email):
user_id = self._next_id
self._next_id += 1
self._storage[user_id] = {"id": user_id, "name": name, "email": email}
return self._storage[user_id]
def…How to Mock Hexagonal Architecture Ports and Adapters in Python
Mock an email adapter in a hexagonal architecture with unittest.mock to test business logic in isolation.
from unittest.mock import Mock
class EmailService:
def send(self, recipient, message):
raise NotImplementedError
class OrderProcessor:
def __init__(self, email_service):
self.email_service = email_service
def process_order(self, order_id, customer_email):
# Business logic
…How to mock the domain center in an onion architecture in Python
Define a repository interface and an in-memory mock to test domain services without touching infrastructure.
from abc import ABC, abstractmethod
from dataclasses import dataclass
from typing import Dict, List, Optional
@dataclass
class Order:
id: int
customer: str
items: List[str]
total: float
class OrderRepository(ABC):
@abstractmethod
def find_by_id(self, order_id: int) -> Optional[Order]:
…Python MVC Pattern Example (Model-View-Controller)
A minimal, runnable Model-View-Controller (MVC) example in pure Python that separates data, presentation, and logic.
class Model:
def __init__(self):
self.data = {"title": "Initial Title", "content": "Initial Content"}
def get_data(self):
return self.data
def update_data(self, title=None, content=None):
if title:
self.data["title"] = title
if content:
self.data["c…How to Demonstrate the Shared Database Antipattern in Python
This code simulates a shared database where multiple services write and read the same SQLite table, illustrating tight coupling and its pitfalls.
import sqlite3
from pathlib import Path
def create_shared_db(db_path: Path) -> None:
"""Mock demonstrating the shared database antipattern where multiple
services access the same database, causing tight coupling."""
conn = sqlite3.connect(db_path)
cur = conn.cursor()
cur.execute("""
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