Python code explainers

python

from fastapi import FastAPI, WebSocket, WebSocketDisconnect
 
app = FastAPI()

Building a WebSocket chat with FastAPI

websockets broadcast connection-management

Intermediate 9 steps

python

import time
import uuid
 
from django.utils.deprecation import MiddlewareMixin

Attaching per-request context in Django

middleware request lifecycle multi-tenancy

Intermediate 7 steps

python

import random
from typing import Iterator, List

How reservoir sampling picks k items

reservoir-sampling streaming randomness

Intermediate 5 steps

python

import secrets
 
from django.contrib.auth import authenticate, login
from django.core.cache import cache

Two-factor login with OTP in Django

two-factor-auth one-time-passwords caching

Intermediate 9 steps

python

import re
from functools import total_ordering
from typing import Optional

Parsing and comparing semantic versions

regex operator-overloading sorting

Intermediate 7 steps

python

from typing import Any, Sequence, Mapping
 
 
def render_markdown_table(

Rendering an aligned Markdown table in Python

string formatting data transformation closures

Intermediate 8 steps

python

from django.db import connections
from django.db.utils import OperationalError
from django.core.cache import caches
from django.http import JsonResponse

Building a health check endpoint in Django

health check monitoring database

Intermediate 7 steps

python

from enum import Enum
from typing import Annotated
 
from fastapi import FastAPI, Query, Request, status

Custom validation error responses in FastAPI

validation error-handling enums

Intermediate 8 steps

python

from fastapi import Depends, FastAPI, Header, HTTPException, status
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

Chaining tenant dependencies in FastAPI

dependency injection multi-tenancy authentication

Intermediate 7 steps

python

from django.db import models
from django.db.models import F, Sum, DecimalField
from django.db.models.functions import Coalesce

Recomputing order totals in Django

annotations aggregation custom-manager

Intermediate 9 steps

python

import asyncio
import logging
from dataclasses import dataclass

A concurrent batch geocoder in asyncio

asyncio producer-consumer rate-limiting

Advanced 8 steps

python

import functools
import inspect
from typing import get_type_hints, get_origin, get_args, Union

A runtime type checker from annotations

decorators runtime-validation type-hints

Advanced 8 steps

python

import hashlib
import json
from functools import wraps
from flask import g, request, jsonify, current_app

Building an idempotency decorator in Flask

idempotency decorators redis

Advanced 7 steps

python

from flask import Flask, request, redirect, current_app
from werkzeug.middleware.proxy_fix import ProxyFix
 
app = Flask(__name__)

Enforcing HTTPS behind a proxy in Flask

https middleware security-headers

Intermediate 7 steps

python

import fnmatch
from collections import defaultdict
from typing import Any, Callable

A pattern-matching event bus in Python

pub-sub decorators pattern-matching

Intermediate 8 steps

python

from typing import Iterable
 
 
def jaccard_similarity(tags_a: Iterable[str], tags_b: Iterable[str]) -> float:

Ranking tag sets by Jaccard similarity

set-operations similarity-metric generators

Intermediate 5 steps

python

from django import forms
from django.contrib.auth import get_user_model
from django.shortcuts import redirect
from formtools.wizard.views import SessionWizardView

Building a multi-step form with Django wizards

form-wizard multi-step-forms session-state

Intermediate 8 steps

python

import functools
import time
 
from flask import current_app

Retrying deadlocked DB writes in Flask

decorators retry exponential-backoff

Intermediate 6 steps