Python

Basic SELECT queries only get you so far. Real applications need joins, aggregations, and complex filtering. This tutorial covers the SQL features you will use every day. We assume you have PostgreSQL running. See PostgreSQL Setup and Basics if you need to set that up first. Sample Schema Let’s use a simple e-commerce schema for all examples: CREATE TABLE users ( id uuid DEFAULT gen_random_uuid() PRIMARY KEY, name text NOT NULL, email text UNIQUE NOT NULL, created_at timestamptz DEFAULT NOW() ); CREATE TABLE orders ( id uuid DEFAULT gen_random_uuid() PRIMARY KEY, user_id uuid REFERENCES users(id), status text NOT NULL DEFAULT 'pending', total decimal(10, 2) NOT NULL, created_at timestamptz DEFAULT NOW() ); CREATE TABLE order_items ( id uuid DEFAULT gen_random_uuid() PRIMARY KEY, order_id uuid REFERENCES orders(id), product text NOT NULL, quantity integer NOT NULL, price decimal(10, 2) NOT NULL ); JOINs JOINs combine rows from multiple tables based on a related column. ...

PostgreSQL is the most popular open-source database in the world. It is fast, reliable, and packed with features. This tutorial gets you up and running with PostgreSQL 17. We use Docker so you do not need to install PostgreSQL on your computer. Start PostgreSQL with Docker docker run -d \ --name postgres17 \ -e POSTGRES_PASSWORD=secret \ -e POSTGRES_USER=admin \ -e POSTGRES_DB=myapp \ -p 5432:5432 \ postgres:17 This starts PostgreSQL 17 in the background. Let’s break down the options: ...

Clean code is code that other developers can read and understand quickly. It is not about cleverness. It is about clarity. The best code reads like a well-written paragraph. These 10 rules will make your code better immediately. Each rule includes bad and good examples in both Kotlin and Python. You can apply these today, no matter what language you use. Rule 1: Use Descriptive Names Names should tell you what a variable, function, or class does. If you need a comment to explain a name, the name is wrong. ...

Backend development is the engine behind every app and website. In 2026, the backend landscape is more exciting than ever. New frameworks, better tooling, and AI assistants make it faster to build production-ready APIs. This roadmap covers everything you need to become a backend developer. It includes language choices, databases, deployment, and a realistic timeline. Follow the stages in order for the best results. Why Backend Development in 2026? Every mobile app, website, and service needs a backend. The demand is constant and growing. Here is what makes 2026 special: ...

Python is one of the most popular languages in 2026. It dominates AI/ML, web development, data science, and automation. This guide covers the 30 most common Python interview questions. Answers are short and practical with code examples. Quick Reference — Python Key Features Feature Description Dynamically typed No need to declare types (but type hints are recommended) Interpreted Runs line by line, no compilation step GIL Global Interpreter Lock limits true multi-threading Indentation-based Uses whitespace instead of braces for blocks Duck typing “If it walks like a duck…” — type is determined by behavior Garbage collected Automatic memory management with reference counting Batteries included Large standard library for common tasks Package manager pip (or uv for faster installs) Beginner Questions (1-12) 1. What is Python? Python is a high-level, interpreted, dynamically-typed programming language. It was created by Guido van Rossum and released in 1991. Python emphasizes readability with its use of indentation. It is widely used for web development, AI/ML, automation, and data analysis. ...

Python and Rust could not be more different. Python is the world’s most popular language — easy, flexible, everywhere. Rust is the most loved language — fast, safe, precise. But here is the interesting part: in 2026, they are not competitors. They are partners. Many of the fastest Python tools are actually written in Rust underneath. This guide will help you understand when to use each language and when to use them together. ...

Last time we built a CLI todo app in 35 minutes. That was a local app. This time, we go bigger: a REST API that runs on the web. The goal: build a bookmark manager API with CRUD operations, pagination, search, rate limiting, tests, and a Docker setup. All with Claude Code prompts. Deploy it and get a live URL. Total time: 52 minutes from empty folder to deployed API. What We’re Building A bookmark manager REST API with these features: ...

Enough theory. Let us build something real. In this article, you will build a complete CLI tool using AI — from the initial description to a published package on PyPI. Every prompt, every AI response, and every manual fix is shown. You will see where AI excels, where it struggles, and how to handle both. The project: linkcheck — a markdown link checker that scans your documentation files and reports broken links. It is a small, useful tool with enough complexity to show real patterns. ...

Can you build a working CLI application in 30 minutes using only Claude Code? I tried it. Here is exactly what happened — every prompt, every mistake, and the final result. The goal was simple: start with an empty folder, talk to Claude Code in the terminal, and end up with a fully working todo app. No manual coding. Just prompts. Spoiler: it took 35 minutes, not 30. But the result was better than expected. ...

These ten concepts appear in almost every Python project. If you know all of them, you can read and write real Python code. If you are missing one, that is the one that trips you up on every project. 1. Variables and Data Types Python infers types automatically. No declaration needed. name: str = "Alex" age: int = 25 score: float = 9.5 active: bool = True nothing = None print(type(name)) # <class 'str'> The four built-in collection types: numbers = [1, 2, 3] # list — ordered, mutable point = (10, 20) # tuple — ordered, immutable tags = {"python", "dev"} # set — unique items user = {"name": "Alex", "age": 25} # dict — key/value pairs Use type() to check the type of any variable at runtime. Use type hints for documentation and IDE support. ...