1 Languages

Every entry filed under Languages and its subtopics.

42 entries

0001 Virtual environments with venv A virtual environment is a private folder of Python packages for one project, so projects never fight over versions. Create one with… Beginner · Concept · Any system Article Environments & packages 15 Oct 2026
0002 Python cheat sheet: strings, lists, dicts and f-strings The everyday methods for text, lists and dictionaries, plus f-string formatting and comprehensions, each with a one-line example you can paste into… Beginner · Reference · Any system Article Basics 15 Oct 2026
0003 pathlib cheat sheet: files and folders in Python pathlib.Path is the modern way to build paths, read and write files, and list or search folders in Python. This page lists… Beginner · Reference · Any system Article Files & automation 15 Oct 2026
0004 Logging instead of print The logging module gives every message a level, a timestamp and a destination you can change without editing code. It is the… Intermediate · Concept · Any system Article Files & automation 15 Oct 2026
0005 Dataclasses in depth @dataclass writes __init__, __repr__ and __eq__ for classes that mainly hold data. Learn defaults, default_factory, frozen and ordered classes, __post_init__ validation, slots… Advanced · Concept · Any system Article Basics 15 Oct 2026
0006 Testing with pytest: first tests, fixtures and parametrize pytest runs plain functions whose names start with test_ and reports every failing assert in detail. This guide covers setup, assertions, exceptions,… Intermediate · How-to · Any system Article Testing 15 Oct 2026
0007 Fix: ModuleNotFoundError: No module named ‘…’ Python cannot find a module you import. Usually the package was installed into a different interpreter or virtual environment than the one… Beginner · Fix · Any system Article Common errors · Environments & packages 15 Oct 2026
0008 Fix: TypeError: ‘NoneType’ object is not subscriptable You used [ ] on a value that is None. Something you expected to return a list, dict or match returned nothing.… Beginner · Fix · Any system Article Common errors 15 Oct 2026
0009 CSV to JSON converter A small command-line tool that turns a CSV file into a JSON array of objects, with optional number detection, custom delimiters and… Beginner · How-to · Any system Script CSV & JSON · Files & automation 15 Oct 2026
0010 Find duplicate files by content Scans folders and lists files with identical content, using file size first and SHA-256 hashes second. It is read-only and only reports… Intermediate · How-to · Any system Script Files & automation 15 Oct 2026
0011 Bootstrap a new Python project with a venv A Bash script that creates a project folder with a virtual environment, .gitignore, requirements.txt and a starter main.py, then runs it to… Intermediate · How-to · Linux, macOS Script Environments & packages 15 Oct 2026
0012 Requests: HTTP for humans Requests is the classic Python library for calling web APIs and downloading pages, with a simple API for GET and POST requests,… Any system Repo Files & automation · Making requests 15 Oct 2026
0013 pytest pytest is the de facto standard test runner for Python: plain functions with assert, detailed failure reports, fixtures, parametrization and a large… Any system Repo Testing 15 Oct 2026
0014 uv: Python package and project manager uv is a very fast Python package and project manager written in Rust. It replaces pip, venv and related tools, manages lock… Any system Repo Environments & packages 15 Oct 2026
0015 Ruff: Python linter and formatter Ruff is a fast Python linter and code formatter written in Rust. It catches bugs such as undefined names and unused imports… Any system Repo Common errors · Testing 15 Oct 2026
0016 let, const and var: variables and scope in JavaScript Use const by default, let when a value must change, and avoid var. The difference is about scope: where a variable is… Beginner · Concept · Any system Article Basics 15 Oct 2026
0017 JavaScript array methods cheat sheet: map, filter, reduce and friends A quick reference for the array methods you use every day, with what each one returns and whether it changes the original… Beginner · Reference · Any system Article Basics 15 Oct 2026
0018 Promises and async/await explained A promise is a placeholder for a value that arrives later. async/await lets you write code that waits for promises as if… Intermediate · Concept · Any system Article Async code 15 Oct 2026
0019 fetch with timeout, retries and proper error handling A reusable fetchJson helper for Node 20+ and browsers that adds a timeout, retries with backoff for temporary failures, and clear errors… Intermediate · How-to · Any system Script Async code · Making requests 15 Oct 2026
0020 Debounce and throttle functions in plain JavaScript Two small dependency-free helpers that limit how often a function runs: debounce waits for a pause, throttle runs at most once per… Intermediate · How-to · Any system Script Patterns 15 Oct 2026
0021 Read and write files in Node.js with fs/promises A complete Node script that walks a folder, reads text files, and writes a JSON report safely, showing the everyday fs/promises calls… Beginner · How-to · Any system Script Node.js 15 Oct 2026
0022 Build a small Node.js CLI with util.parseArgs A complete, dependency-free command-line tool in Node: options and flags with parseArgs, input from files or a pipe, help text, and meaningful… Intermediate · How-to · Any system Script Node.js 15 Oct 2026
0023 Run async tasks with a concurrency limit A small mapLimit helper that runs an async function over many items with at most N in flight, keeps result order, stops… Advanced · How-to · Any system Script Async code 15 Oct 2026
0024 TypeScript basics: types, interfaces, unions and narrowing TypeScript adds type annotations to JavaScript and checks them before your code runs. These are the core ideas you need to read… Beginner · Concept · Any system Article Basics 15 Oct 2026
0025 Regular expressions cheat sheet (JavaScript flavor) The regex syntax you actually use, from character classes and quantifiers to groups, lookarounds and flags, with the JavaScript methods that apply… Beginner · Reference · Any system Article Basics · Basics 15 Oct 2026
0026 Fix: TypeError: Cannot read properties of undefined (reading ‘x’) You tried to read a property from a value that is undefined or null. Find which value is missing, then guard it… Beginner · Fix · Any system Article Basics · Common errors 15 Oct 2026
0027 Fix: SyntaxError: Cannot use import statement outside a module The file uses ES module import syntax, but Node or the browser is loading it as a classic script or CommonJS. Tell… Intermediate · Fix · Any system Article Common errors · Node.js 15 Oct 2026
0028 Node.js The source of the Node.js runtime: a JavaScript engine (V8) plus APIs for files, networking, processes and more, used to run JavaScript… Linux, macOS, Windows Repo Node.js 15 Oct 2026
0029 TypeScript Microsoft's TypeScript language and compiler: typed JavaScript that compiles to plain JavaScript, plus the language service that powers editor features. Any system Repo Basics 15 Oct 2026
0030 Axios A promise-based HTTP client for browsers and Node.js with interceptors, automatic JSON handling, request cancellation and a consistent API in both environments. Any system Repo Async code · Making requests 15 Oct 2026
0031 Lodash A JavaScript utility library with helpers for arrays, objects, strings and functions, including debounce, throttle, deep cloning and safe property access. Any system Repo Patterns 15 Oct 2026
0073 Fix: json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0) Python's json module found nothing it could parse at the very first character. The input is usually empty, HTML, or already consumed.… Beginner · Fix · Any system Article Common errors · CSV & JSON 15 Oct 2026
0074 pandas basics: read a CSV, filter rows and summarize with groupby Load a CSV into a pandas DataFrame, inspect it, filter rows with conditions, and compute totals per group, with the SQL equivalent… Intermediate · How-to · Any system Article Data analysis · Files & automation 15 Oct 2026
0075 CSV to JSON converter (Python, standard library) Convert any CSV file with a header row into a JSON array or JSON Lines. Handles quoted fields, a byte order mark,… Beginner · How-to · Any system Script CSV & JSON · Files & automation 15 Oct 2026
0084 Tiny JSON echo server for testing HTTP clients A standard-library Python server that echoes back the method, path, query, headers, and body of every request, and can return any status… Intermediate · How-to · Any system Script Files & automation · Making requests 15 Oct 2026
0085 fetch with timeout, retries, and exponential backoff A drop-in fetch wrapper that times out slow requests, retries network errors and 429/5xx responses with jittered exponential backoff, and honors Retry-After. Advanced · How-to · Any system, Browser Script Async code · Making requests 15 Oct 2026
0087 CORS explained: why the browser blocks your request CORS is the browser rule that decides whether JavaScript on one origin may read a response from another. The server opts in… Intermediate · Concept · Browser Article Async code · Making requests 15 Oct 2026
0088 Fix: Access to fetch at ‘…’ from origin ‘…’ has been blocked by CORS policy The browser refused to give your script a cross-origin response because the server did not send the right Access-Control-* headers. Fix it… Intermediate · Fix · Browser Article Common errors · Making requests 15 Oct 2026
0096 Flask (pallets/flask) A lightweight Python web framework for building websites and JSON APIs, with routing, request handling, and templates, and extensions for everything else. Any system Repo Python · Web frameworks 15 Oct 2026
0097 Express (expressjs/express) A minimal and flexible web framework for Node.js, built around routes and middleware, and the foundation of countless APIs and other frameworks. Any system Repo Node.js · Web frameworks 15 Oct 2026
0261 Build a Python command-line to-do app: from empty folder to installable command Create a small to-do tool in Python with argparse and JSON storage, test it with pytest and package it with pyproject.toml so… Beginner · Tutorial · Any system Article Environments & packages · Files & automation · Testing 15 Oct 2026
0263 Build a notes REST API with plain Node.js: CRUD, validation, status codes and CORS Write a small JSON API for notes using only Node.js built-ins: create, read, update and delete, input validation, correct HTTP status codes,… Intermediate · Tutorial · Any system Article Making requests · Node.js · Status codes 15 Oct 2026