Python code explainers

python

import ijson
from decimal import Decimal

Streaming JSON aggregation with ijson

streaming json-parsing generators

Intermediate 7 steps

python

import os
import uuid
 
from flask import Blueprint, current_app, jsonify, request

Handling secure file uploads in Flask

file-upload validation blueprints

Intermediate 8 steps

python

from django.core.cache import cache
from django.db.models import Count, Sum, Q
from django.utils import timezone

Caching a Django dashboard aggregate query

caching aggregation conditional-queries

Intermediate 7 steps

python

import time
from contextlib import contextmanager

A reusable timing context manager in Python

context-manager timing generators

Intermediate 5 steps

python

import os
from datetime import datetime, timezone
 
import jwt

JWT bearer auth as a FastAPI dependency

authentication jwt dependency-injection

Intermediate 7 steps

python

import logging
import traceback
 
from flask import Blueprint, jsonify, request

Centralized JSON error handling in Flask

error-handling blueprints json-api

Intermediate 5 steps

python

from datetime import datetime, date
from decimal import Decimal
from flask import Flask, jsonify
from flask.json.provider import DefaultJSONProvider

Serializing SQLAlchemy models in Flask JSON

serialization orm json

Intermediate 6 steps

python

import requests
from requests.adapters import HTTPAdapter
from urllib3.util.retry import Retry

Building a resilient requests Session

retries backoff http-client

Intermediate 7 steps

python

from datetime import datetime
from fastapi import APIRouter, Depends, HTTPException, status
from pydantic import BaseModel, ConfigDict, EmailStr
from sqlalchemy.orm import Session

Building a users router in FastAPI

routing serialization dependency-injection

Intermediate 7 steps

python

import json
from dataclasses import dataclass, field, asdict
from datetime import datetime
from typing import Any

JSON round-tripping with Python dataclasses

dataclasses serialization json

Intermediate 6 steps

python

import re
 
from django.core.exceptions import ValidationError
from django.core.validators import RegexValidator

Building a deconstructible validator in Django

validation regex deconstructible

Intermediate 7 steps

python

from dataclasses import dataclass
from typing import Optional
 
from sqlalchemy import select, func

Building a pagination helper with SQLAlchemy

pagination dataclass computed-properties

Intermediate 8 steps

python

from datetime import timedelta
 
from django.contrib.sessions.models import Session
from django.core.management.base import BaseCommand

A batched session-cleanup command in Django

management-command batch-processing database-cleanup

Intermediate 7 steps

python

import re
from email_validator import validate_email, EmailNotValidError
 
_DISPOSABLE_DOMAINS = {

Normalizing signup emails in Python

validation normalization data-cleaning

Intermediate 8 steps

python

import time
from concurrent.futures import ThreadPoolExecutor, as_completed
from pathlib import Path

Parallel file downloads with a thread pool

concurrency thread-pool streaming-io

Intermediate 8 steps

python

from datetime import datetime
from zoneinfo import ZoneInfo

Timezone-safe datetime handling in Python

timezones datetime normalization

Intermediate 4 steps

python

import shutil
import uuid
from pathlib import Path

Safe avatar uploads in FastAPI

file-upload validation streaming

Intermediate 8 steps

python

from django.db.models import Prefetch, Count
from django.views.generic import ListView
 
from .models import Article, Comment

Building an efficient article list in Django

orm query-optimization prefetching

Intermediate 6 steps