Python code explainers

python

import time
import logging
from threading import Lock

Rate-limiting noisy logs in Python

throttling thread-safety logging

Intermediate 6 steps

python

import gzip
from fastapi import FastAPI, Request, Response
from starlette.middleware.base import BaseHTTPMiddleware
from starlette.types import ASGIApp

Custom gzip middleware in FastAPI

middleware http-compression content-negotiation

Intermediate 9 steps

python

from collections import Counter
 
import numpy as np
from PIL import Image

Extracting a color palette with K-means

clustering image-processing kmeans

Intermediate 7 steps

python

import re
 
from flask_wtf import FlaskForm
from wtforms import StringField, TextAreaField, PasswordField

Cleaning form input with Flask-WTF filters

form validation input sanitization filters

Intermediate 8 steps

python

from datetime import datetime, timezone
 
from flask import abort
from sqlalchemy import Column, DateTime

Soft deletes with a custom SQLAlchemy Query in Flask

soft-delete mixin query-subclass

Advanced 7 steps

python

class TrieNode:
    __slots__ = ("children", "is_word")
 
    def __init__(self):

Building a prefix trie in Python

trie tree-traversal recursion

Intermediate 7 steps

python

from flask import Blueprint, request, jsonify, abort
from sqlalchemy import update
 
from .models import db, Document

Optimistic locking in a Flask PATCH endpoint

optimistic-locking concurrency rest-api

Intermediate 7 steps

python

import os
import re
from flask import Blueprint, request, Response, abort

HTTP range requests for video streaming in Flask

http-range-requests streaming generators

Intermediate 8 steps

python

from io import BytesIO
from flask import Blueprint, abort, send_file
from reportlab.lib.pagesizes import LETTER
from reportlab.lib.units import inch

Streaming a generated PDF from a Flask route

pdf generation in-memory buffer file download

Intermediate 8 steps

python

from celery import shared_task, signature
from django.core.mail import send_mail
 
from .models import Report, ReportExport

Chaining Celery tasks in Django

asynchronous tasks task chaining retries

Intermediate 8 steps

python

import base64
import json
from flask import Blueprint, request, jsonify, url_for, abort
from sqlalchemy import and_, or_

Cursor pagination in a Flask API

cursor-pagination keyset-pagination rest-api

Advanced 9 steps

python

from flask import Flask, g, current_app
from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session, sessionmaker

Scoped SQLAlchemy sessions in Flask

database session-management connection-pooling

Intermediate 6 steps

python

import re
from starlette.datastructures import URL
from starlette.middleware.base import BaseHTTPMiddleware
from starlette.responses import RedirectResponse

URL normalization middleware in FastAPI

middleware http-redirects url-canonicalization

Intermediate 8 steps

python

import bleach
 
ALLOWED_TAGS = [
    "a", "b", "strong", "i", "em", "u",

Sanitizing user HTML with bleach

sanitization xss-prevention whitelisting

Intermediate 5 steps

python

from flask import Flask, request, Response
from prometheus_client import Counter, Histogram, generate_latest, CONTENT_TYPE_LATEST
import time

Instrumenting a Flask app with Prometheus

metrics observability middleware

Intermediate 6 steps

python

from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField, BooleanField
from wtforms.validators import (
    DataRequired,

Building a signup form with Flask-WTF

form validation declarative fields validators

Intermediate 7 steps

python

from django.db import models
 
 
class Order(models.Model):

Tracking field changes in a Django model

change-tracking audit-log model-lifecycle

Intermediate 8 steps

python

from fastapi import APIRouter, Depends, HTTPException, status
 
from app.config import settings
from app.dependencies import get_current_user

Gating a FastAPI route behind a feature flag

feature-flags dependency-injection authorization

Intermediate 7 steps