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Python Code Samples

Medium snippets you can copy, study, and run in the browser editor.

76 matches
Database scaling & optimization medium

How to Eager Load with JOIN to Reduce N+1 Queries in Python

Demonstrates eager loading with a SQL JOIN to reduce N+1 query patterns down to a single database call when fetching related data.

eager-loading n-plus-1 join
Python 
import sqlite3


def eager_load_join_reduce(mock_db_path=":memory:"):
    """Demonstrate eager loading where joins reduce query count from N+1 to 1."""
    conn = sqlite3.connect(mock_db_path)
    cursor = conn.cursor()
    cursor.executescript(
        """
        CREATE TABLE authors (id INTEGER PRIMARY KEY, name TE…
16 0 Open
Database scaling & optimization medium

How to mock batch commit of transactions in Python

Simulate a transaction batch writer with commit, rollback, and summary logic to test database write patterns without a real database.

transactions mock batch
Python 
import json
from datetime import datetime, timezone

class TransactionBatch:
    def __init__(self):
        self.pending = []
        self.committed = []
        self._log = []

    def add(self, operation):
        self.pending.append(operation)

    def commit(self):
        if not self.pending:
            return …
16 0 Open
Database scaling & optimization medium

Mock CQRS Read/Write Split in Python

Separate order mutations from queries using a read model and write model to mock CQRS-style separation of concerns.

cqrs read-write dataclass
Python 
from dataclasses import dataclass, field
from typing import List, Dict


@dataclass
class Order:
    id: int
    amount: float
    status: str = "pending"


class OrderWriteModel:
    """Handles all mutations (writes) to orders."""

    def __init__(self):
        self._orders: Dict[int, Order] = {}
        self._next…
12 0 Open
Production deployment patterns medium

Zero Downtime Migration with Dual Write Pattern in Python

Implement a dual-write pattern that writes user data to both legacy and new systems simultaneously to enable zero-downtime migration.

migration dual-write zero-downtime
Python 
from datetime import datetime
import json


class UserService:
    def __init__(self):
        self.legacy_db = {}
        self.new_db = {}
        self.migration_log = []

    def write_user(self, user_id, name, email):
        # Write to new system first
        user_record = {
            "id": user_id,
           …
13 0 Open

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  3. Run it in the IDE, tweak values, then take a related quiz or tutorial lesson

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Samples are quick reference — one concept per page. For step-by-step teaching, use our Python tutorials. To test yourself, try quizzes or coding challenges. Clean up style with the Python formatter.

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