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19 entries match these filters

• 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
• 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
• 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
• 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
• 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