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fastify — High-Performance Node Web Framework

Package-level reference for the Fastify framework on npm — install, plugin model, Node support, and validation/encapsulation gotchas.
npm package fastify web framework node

anyio — Structured Concurrency Across asyncio and trio

Package-level reference for anyio on PyPI — install, version policy, task groups, cancel scopes, and the API that runs identically on asyncio and trio.
pip package async concurrency networking

attrs — Classes Without Boilerplate

Package-level reference for attrs on PyPI — install, @define vs @attr.s, validators, converters, and comparison with dataclasses.
pip package dataclass language

autogen-agentchat — Microsoft AutoGen v0.4 Multi-Agent SDK

Package-level reference for the autogen-agentchat / autogen-core / autogen-ext family on PyPI plus the legacy pyautogen — install, rename history, versioning, and alternatives.
pip package llm ai agents multi-agent microsoft

black — The Uncompromising Python Formatter

Package-level reference for black on PyPI — install variants, version policy, the [d] and [jupyter] extras, and how it relates to ruff format.
pip package formatting code-quality

cffi — C Foreign Function Interface for Python

Package-level reference for cffi on PyPI — install, ABI vs API modes, build patterns, and integration with system libraries.
pip package binding c ffi

charset-normalizer — Character Encoding Detection

Package-level reference for charset-normalizer on PyPI — what it does, install, integration with requests, version policy, and alternatives.
pip package encoding text http

chromadb — Embedded Vector Database

Package-level reference for chromadb on PyPI — install variants, server/client split, embedding-function extras, and alternative vector stores.
pip package ai vector-search rag embeddings

click — Composable Command-Line Builder

Package-level reference for the click CLI toolkit on PyPI — install, version policy, extras, and alternatives.
pip package cli terminal

crewai — Role-Based Multi-Agent Orchestration

Package-level reference for the crewai library on PyPI plus the crewai-tools companion — install, versioning, and multi-agent alternatives.
pip package llm ai agents multi-agent

cryptography — Recipes and Hazmat for Python Crypto

Package-level reference for the cryptography library on PyPI — install, version policy, Fernet, asymmetric keys, X.509, and TLS contexts.
pip package crypto security tls

django — The Batteries-Included Web Framework

Package-level reference for Django on PyPI — install variants, LTS release cadence, ecosystem companions, and alternatives.
pip package web api

dspy — Declarative LLM Programming

Package-level reference for DSPy on PyPI — the dspy / dspy-ai rename, install variants, version policy, and alternatives.
pip package ai llm

duckdb — Embedded Analytical SQL

Package-level reference for duckdb — install, versioning, extensions, and gotchas. In-process columnar OLAP for Python.
pip package duckdb sql analytics

fastapi — Modern ASGI API Framework

Package-level reference for FastAPI on PyPI — install variants, version policy, the `[all]` extra, ecosystem companions, and alternatives.
pip package web async api

flask — The WSGI Microframework

Package-level reference for Flask on PyPI — install variants, version policy, extension ecosystem, and alternatives.
pip package web api

fsspec — Filesystem Spec Abstraction

Package-level reference for fsspec on PyPI — install, protocols, chained URIs, caching layers, and integration with pandas / dask.
pip package fs storage

google-genai — Google Gemini SDK (successor to google-generativeai)

Package-level reference for google-genai (the current Gemini SDK) and its predecessor google-generativeai — install, auth, versioning, and alternatives.
pip package llm ai google gemini api

guidance — Programmatic LLM Output Control

Package-level reference for the guidance library on PyPI — install, LLM-provider extras, versioning, and alternatives like instructor and outlines.
pip package llm ai structured-output prompting

httpx — Async-Capable HTTP Client

Package-level reference for httpx on PyPI — install variants, version policy, extras, transport options, and alternatives.
pip package http async networking

idna — Internationalised Domain Names

Package-level reference for idna on PyPI — IDNA2008 vs UTS46, encode/decode, install, integration with requests / urllib3, alternatives.
pip package dns unicode networking

importlib-metadata — Backport of stdlib importlib.metadata

Package-level reference for importlib-metadata on PyPI — install, distribution lookups, entry points, and the stdlib relationship from Python 3.10+.
pip package language

jinja2 — Python Template Engine

Package-level reference for Jinja2 on PyPI — install, version policy, autoescape gotchas, sandboxing, and the template features behind Flask, Ansible, and Sphinx.
pip package template web rendering

langchain — LLM Application Framework Family

Package-level reference for the langchain family on PyPI — install variants, partner packages, version churn, and alternatives.
pip package llm ai langchain agents rag

langsmith — LLM Observability SDK

Package-level reference for the langsmith SDK on PyPI — install, versioning, env-var setup, and observability alternatives.
pip package llm ai observability evaluation tracing

litestar — High-Performance ASGI Framework

Package-level reference for Litestar on PyPI — install variants, version policy, the `[full]` extra, ecosystem companions, and alternatives.
pip package web async api

loguru — Zero-Config Structured Logging

Package-level reference for loguru on PyPI — install variants, version policy, and how it coexists with (does not replace) the stdlib logging module.
pip package logging debugging

modin — Drop-in Parallel pandas

Package-level reference for modin — install, backend extras, versioning, and gotchas. Speeds up existing pandas code with a one-line import swap.
pip package modin pandas parallel

mypy — Reference Static Type Checker for Python

Package-level reference for mypy on PyPI — install variants, Python compat, the types-* stub-package ecosystem, and alternatives.
pip package typing static-analysis

numpy — N-Dimensional Array Foundation

Package-level reference for numpy — install, versioning, ABI breaks, extras, and gotchas. The bedrock of the Python scientific stack.
pip package numpy arrays scientific

packaging — Version Parsing and Requirement Specifiers

Package-level reference for packaging on PyPI — Version, SpecifierSet, Requirement, markers, install, alternatives.
pip package versioning metadata pep

pandas — DataFrames for Python

Package-level reference for pandas — install, versioning, Python compatibility, extras, and gotchas. The de-facto DataFrame library on PyPI.
pip package pandas dataframes data

Pillow — Friendly PIL Fork for Image I/O

Package-level reference for Pillow on PyPI — install variants, format-specific native deps, version policy, and alternatives.
pip package images imaging filesystem

platformdirs — Cross-Platform User Directories

Package-level reference for platformdirs on PyPI — install, version policy, alternatives, and the per-OS path conventions it returns.
pip package paths filesystem configuration

pluggy — Plugin Framework Behind pytest

Package-level reference for pluggy on PyPI — install, version policy, alternatives, and the hookspec/hookimpl model that powers pytest, tox, and devpi.
pip package plugin extensibility entry-points

polars — Fast DataFrames on Rust + Arrow

Package-level reference for polars — install, versioning, extras, and gotchas. The Rust-powered Arrow-native alternative to pandas.
pip package polars dataframes arrow

pre-commit — Multi-Language Git-Hook Framework

Package-level reference for pre-commit on PyPI — install variants, hook-pinning model, and how it composes with ruff, black, and mypy.
pip package git-hooks code-quality

protobuf — Google Protocol Buffers for Python

Package-level reference for the protobuf package on PyPI — install, backend selection (upb / pure-Python / C++), .proto compilation, and gRPC integration.
pip package serialization rpc

pycparser — Pure-Python C Parser

Package-level reference for pycparser on PyPI — install, AST walking, fake stdlib headers, and use as a cffi dependency.
pip package binding c

pydantic — Type-Driven Data Validation

Package-level reference for Pydantic on PyPI — install variants, v1 vs v2 split, optional extras, and alternatives.
pip package validation json

pygments — Syntax Highlighter Library

Package-level reference for Pygments on PyPI — install, version policy, lexers, formatters, and the pygmentize CLI it ships.
pip package syntax-highlighting formatting docs

python-dateutil — Date Parsing, Deltas, and Recurrence

Package-level reference for python-dateutil on PyPI — parser, relativedelta, rrule, timezone, install, alternatives.
pip package datetime timezone parsing

PyYAML — YAML Parser and Emitter

Package-level reference for PyYAML on PyPI — safe_load vs load, dump, custom tags, install, alternatives like ruamel.yaml.
pip package yaml config parsing

qdrant-client — Python Client for Qdrant

Package-level reference for qdrant-client on PyPI — install variants, server version matching, gRPC vs HTTP, fastembed extras, and alternatives.
pip package ai vector-search rag embeddings

reflex — Full-Stack Python Web Framework

Package-level reference for reflex on PyPI — install variants, Node.js requirement, version policy, and alternatives.
pip package web fullstack ui

requests — The Most-Downloaded Python Package

Package-level reference for the requests HTTP client on PyPI — install variants, version policy, extras, and alternatives.
pip package http networking

rich — Beautiful Terminal Output for Python

Package-level reference for rich on PyPI — install variants, single-file design, version policy, and alternatives.
pip package terminal cli tui

ruff — Rust-Powered Python Linter & Formatter

Package-level reference for ruff on PyPI — install variants, fast-moving version policy, and how a single binary subsumes flake8, isort, pyupgrade, and black.
pip package linting formatting code-quality

scikit-learn — Classical Machine Learning

Package-level reference for scikit-learn — install, versioning, extras, and gotchas. The de-facto classical-ML library on PyPI.
pip package scikit-learn ml modelling

scipy — Scientific Algorithms on NumPy

Package-level reference for scipy — install, versioning, submodules, license caveats, and gotchas. Optimization, statistics, signal processing, and linear algebra.
pip package scipy scientific statistics

sentence-transformers — Embedding & Reranking Models

Package-level reference for the sentence-transformers library on PyPI — install, transformers/torch deps, model registry, and embedding alternatives.
pip package llm ai embeddings rag huggingface

six — Python 2/3 Compatibility (Mostly Legacy in 2026)

Package-level reference for six on PyPI — what it did, why it still appears in dependency trees, and why new code should avoid it.
pip package compatibility legacy python2

SQLAlchemy — The Python SQL Toolkit & ORM

Package-level reference for SQLAlchemy on PyPI — install variants, dialect drivers, version policy, extras, and alternatives.
pip package orm sql database

sqlmodel — Pydantic + SQLAlchemy Fusion

Package-level reference for SQLModel on PyPI — install, version policy, dependencies, and alternatives.
pip package orm sql database

tqdm — Fast, Extensible Progress Bars

Package-level reference for tqdm on PyPI — install variants, notebook extra, version policy, and alternatives.
pip package progress cli async

transformers — Hugging Face Model Library

Package-level reference for the Hugging Face transformers library on PyPI — install extras, backend choice, versioning, and alternatives.
pip package llm ai huggingface nlp ml

typer — Type-Hint-Driven CLI Framework

Package-level reference for the Typer CLI library on PyPI — install variants, version policy, extras, and alternatives.
pip package cli terminal

typing-extensions — Backported and Experimental Typing Features

Package-level reference for typing-extensions on PyPI — what's backported, install, version policy, and migration to stdlib.
pip package typing mypy backport

urllib3 — Low-Level HTTP Client

Package-level reference for urllib3 on PyPI — connection pooling, retries, TLS, version policy, and alternatives.
pip package http networking tls

weaviate-client — Python Client for Weaviate

Package-level reference for weaviate-client on PyPI — install variants, the v3 → v4 API split, gRPC, and alternative vector stores.
pip package ai vector-search rag embeddings

Fastify — Node Web Framework

Fastify is a high-performance Node.js web framework with schema-driven validation, plugin encapsulation, hooks, decorators, and built-in Pino logging — covering routes, plugins, hooks, error handling, and production hardening.
javascript node backend framework fastify web

node:fs — File System

Node.js file system module — the three APIs (callback, sync, promises), reading and writing files, directory operations, watchers, atomic writes, and path module pairing.
javascript node filesystem fs language

node:stream — Streams

Node.js streams — Readable, Writable, Duplex, and Transform, the modern pipeline() API, backpressure, async iterators, Web Streams interop, and patterns for piping files, HTTP bodies, and gzip compression.
javascript node streams pipeline language

PCRE — Perl Compatible Regular Expressions

PCRE2 syntax reference — character classes, quantifiers, anchors, groups, lookarounds, backreferences, flags, and advanced features used in grep, sed, nginx, PHP, and dozens of other tools.
pcre regex grep linux cli patterns web-researched

Design Patterns — Gang-of-Four Essentials and Modern Variants

A practical reference for classic OOP design patterns — Strategy, Observer, Factory, Adapter, Decorator, Repository — with examples in Python, TypeScript, and Go.
design-patterns oop architecture gof refactoring principles

SOLID — Five Principles for Maintainable OO Design

A modern walk-through of the SOLID principles — single responsibility, open-closed, Liskov, interface segregation, dependency inversion — with anti-examples and refactors in TypeScript and Python.
solid oop principles srp ocp lsp isp dip refactoring architecture

argparse — Stdlib CLI Argument Parser

Parse command-line arguments with Python's stdlib argparse module. Covers positional/optional args, subparsers, nargs, validation, mutually exclusive groups, FileType, env-var fallbacks, and argcomplete.
python stdlib cli scripting tooling

dataclasses — Boilerplate-Free Classes

Define typed data containers with @dataclass — frozen, slots, kw_only, default_factory, __post_init__, asdict, replace, and how it compares to attrs, pydantic, NamedTuple, TypedDict.
python stdlib typing

datetime — Dates, Times, Timezones

Work with dates, times, and timezones in Python using the stdlib datetime module and zoneinfo. Covers aware vs naive datetimes, ISO-8601 parsing, strftime/strptime, timedelta arithmetic, and DST handling.
python stdlib time timezones parsing data

Essential Python Packages

Overview of the 34 most useful Python packages — HTTP clients, data science, web frameworks, orchestration, testing, and tooling. Each has its own dedicated page with examples.
python packages pip overview

fastapi — Fast ASGI API Framework

Build high-performance async REST APIs with FastAPI. Covers path params, request bodies, Pydantic models, dependency injection, and auto-generated OpenAPI docs.
python fastapi api async asgi rest openapi pydantic

flask — Micro Web Framework

Build lightweight web apps and REST APIs with Flask. Covers routes, request handling, JSON responses, blueprints, and the debug-server warning.
python flask web api wsgi microframework

httpx — Modern HTTP Client

Make sync and async HTTP requests with httpx. Covers GET/POST, async usage, HTTP/2, streaming, and how it compares to requests.
python httpx http api async networking

Python Installation — Quick-Pick

Choose your OS and get Python installed in minutes. Covers Windows, WSL/Ubuntu, macOS, and Linux with recommended versions and verification steps.
python install

Python Installation — Linux

Install Python 3 on Debian/Ubuntu, Fedora/RHEL, and Arch Linux. Covers package managers, pyenv, and building from source for unsupported distros.
python install linux debian ubuntu fedora arch pyenv

Python Installation — macOS

Install Python 3 on macOS via Homebrew or pyenv. Explains the system-Python warning, PATH precedence, and verification steps.
python install macos homebrew pyenv

Python Installation — Windows

Install Python 3 on Windows via winget or the python.org installer. Covers PATH setup, the py launcher, and verification steps.
python install windows

Python Installation — WSL Ubuntu

Install Python 3 inside WSL2/Ubuntu via apt, the deadsnakes PPA, or pyenv. Covers the python3-venv quirk and version aliasing.
python install wsl ubuntu linux

itertools & functools — Functional Toolbelt

The two stdlib modules every Python developer pairs together — iterator algebra (chain, groupby, batched, pairwise) and function plumbing (lru_cache, partial, reduce, singledispatch, cached_property).
python stdlib functional itertools functools

json — Stdlib JSON Encoder/Decoder

Encode and decode JSON in Python with the stdlib json module. Covers dumps/loads, indent/sort_keys/separators, custom default= and JSONEncoder, object_hook decoding, JSONL streaming, and orjson/ujson/msgspec comparison.
python stdlib json data serialization parsing

logging — Stdlib Logging

Configure Python's built-in logging module — loggers, handlers, formatters, dictConfig, rotation, structured records, and how it compares to loguru.
python stdlib logging

pdb — Python Debugger

Pause, inspect, and step through Python programs with pdb. Covers breakpoint(), command reference, post-mortem debugging, conditional breakpoints, and enhanced alternatives like ipdb, pdbpp, and pudb.
python pdb debugging stdlib repl tooling

poetry — Dependency Management & Packaging

Manage Python project dependencies, virtual environments, and package publishing with Poetry. Covers pyproject.toml, lockfiles, groups, and publishing to PyPI.
python poetry packaging dependencies pyproject lockfile

pre-commit — Git Hooks for Linters and Formatters

Run linters, formatters, and validators automatically on every git commit. Covers .pre-commit-config.yaml, essential hooks (ruff, mypy, check-yaml), autoupdate, and CI integration.
python pre-commit git-hooks workflow ci code-quality tooling

pydantic — Data Validation

Validate and parse data at runtime using Python type hints with Pydantic v2. Covers BaseModel, field validators, nested models, and JSON serialization.
python pydantic validation types models serialization

pyproject.toml — Modern Python Project Config

The canonical config file for modern Python projects — [project] metadata, [build-system] backends (setuptools, hatchling, pdm-backend, poetry-core, flit-core), [tool.*] sections, dynamic versioning, scripts, building, and publishing.
python packaging pyproject toml build pep-621

re — Python Regular Expressions

Python's built-in regex module — compile vs not, match/search/findall/finditer/sub, named groups, lookarounds, verbose mode (re.X), and how it differs from PCRE.
python stdlib regex re patterns

requests — HTTP for Humans

Make HTTP requests in Python with the requests library. Covers GET/POST, JSON, sessions, authentication, retries, and common pitfalls.
python requests http api networking

scikit-learn — Classical Machine Learning

Build classical ML pipelines with scikit-learn. Covers the estimator API, train_test_split, Pipeline, ColumnTransformer, cross-validation, metrics, and model persistence.
python scikit-learn ml data-science pipelines modeling classification

streamlit — Data Apps in Pure Python

Build interactive web apps for data and ML in pure Python. Covers widgets, layout, session state, caching, multipage apps, and deployment patterns.
python streamlit ui dataviz prototyping web frontend

subprocess — Spawning Processes

Run external commands from Python with subprocess. Covers run vs Popen, capture_output, streaming, pipes, timeouts, env/cwd overrides, and shlex quoting safety.
python stdlib shell

typing — Advanced Type Hints

Go beyond list[int] and str | None. Covers Protocol, TypeVar bounds, ParamSpec, Concatenate, Self, Annotated, TypedDict with NotRequired/Required, TypeAlias, TypeGuard, TypeIs, cast, assert_type, and reveal_type.
python typing types stdlib mypy generics protocol

uv — Fast Python Package Manager

Install packages and manage virtual environments blazingly fast with uv. Covers uv pip, uv venv, uv run, uv init, and how it compares to pip and poetry.
python uv pip packaging venv tools astral

Virtual Environments — venv

Create, activate, and manage Python virtual environments with venv. Covers activation for every shell, pip usage, requirements files, and cleanup.
python venv virtualenv pip packaging

Branded Types — Nominal Typing in a Structural System

Branded (a.k.a. nominal, opaque, tagged) types add a phantom marker to a primitive so the compiler refuses to mix two strings — useful for IDs, units, validated input, and money. Covers hand-rolled brands, type-fest's Opaque/Tagged, Zod's .brand(), class-based brands, and runtime validation pairings.
typescript types patterns language branded

Declaration Merging — Interfaces, Namespaces, Modules, Globals

Deep dive into TypeScript declaration merging — interface merging, namespace + class, namespace + function, module augmentation, global augmentation, and the Express Request pattern.
typescript declarations modules patterns advanced

Discriminated Unions — Tagged Variants & Exhaustiveness

Discriminated unions model finite states with a shared literal tag, enabling exhaustive narrowing in switch statements, Result-style error handling, reducer actions, and pattern-matched API responses.
typescript types patterns narrowing language

.d.ts Files — Ambient Declarations, Asset Imports, Module Typing

Authoring .d.ts files — ambient declarations, declare module 'foo', asset typing (*.svg?raw), declare global, triple-slash refs, and the home-hero.svg?raw pattern used in this project.
typescript declarations modules ambient dts

infer Keyword — Extracting types from patterns

TypeScript's infer keyword declares a fresh type variable inside a conditional type, letting you pull a sub-type out of a matched shape. It powers ReturnType, Parameters, Awaited, and most advanced type extractors.
typescript types advanced language

satisfies Operator — Type-check without widening

TypeScript's satisfies operator checks a value against a type while preserving its narrow literal inferred type. The middle ground between an annotation that widens and an as cast that lies.
typescript types operators language

Structural Typing — Duck Typing at the Type Level

Understand TypeScript's structural type system — assignability is based on shape, not name; excess property checks are the one exception; nominal typing requires branded types or class privates.
typescript types concepts language

Template Literal Types — String Algebra at the Type Level

Template literal types let TypeScript pattern-match and synthesize string types — covering Uppercase/Lowercase intrinsics, infer-based parsers (Split, Join, CamelCase), route-param extraction, JSON path keys, and typed i18n helpers.
typescript types advanced template-literals language

TypeScript Modules — module, moduleResolution, .mts / .cts

Deep dive into TypeScript's module system — module/moduleResolution pairs, .mts/.cts file extensions, NodeNext vs Bundler resolution, paths, and tsconfig extends.
typescript modules esm nodenext tooling

typeof & keyof — Type-level operators

TypeScript's typeof promotes a runtime value into the type position; keyof extracts the union of property keys. Together they form the backbone of type-safe lookups, enum-from-object patterns, and inferred shapes.
typescript types operators language

Sentence Transformers — Embeddings, Search & Fine-Tuning

Comprehensive reference for the sentence-transformers Python library — embeddings, similarity, clustering, retrieval, fine-tuning, and popular models (BGE, E5, GTE, Nomic, Jina).
python embeddings nlp sentence-transformers semantic-search vector-db rag clustering fine-tuning bge e5 gte nomic jina

AutoGen — Multi-Agent Conversations

Build multi-agent AI systems with Microsoft AutoGen. Covers agents, group chats, code execution, tool registration, async runtimes, and LLM configuration.
python autogen agents llm ai microsoft multi-agent code-execution

ChromaDB — Embedded Vector Database

Store and query vector embeddings locally or over a network with ChromaDB. Covers client types, collections, add, query, metadata filters, embedding functions, and LangChain/LlamaIndex integration.
python chromadb vector-database embeddings rag ai similarity-search

crewAI — Role-Based Agent Crews

Orchestrate teams of role-playing AI agents with crewAI. Covers agents, tasks, crews, tools, LLM selection, memory, YAML config, and the kickoff lifecycle.
python crewai agents llm ai multi-agent rag tools

google-generativeai — Gemini SDK

Call Google's Gemini models from Python for text, multimodal, streaming, chat, function calling, and embeddings. Covers the genai SDK, safety settings, file API, and async usage.
python google gemini llm ai multimodal api

guidance — Constrained LLM Generation

Interleave Python control flow with LLM generation and enforce structured output using guidance. Covers gen(), select(), chat blocks, regex constraints, JSON schemas, and token healing.
python guidance llm ai structured-output constrained-generation transformers

LangChain — LLM Application Framework

Build LLM-powered pipelines with LangChain. Covers LCEL chains, chat models, prompts, output parsers, tools, agents, retrievers, memory, and streaming.
python langchain llm ai rag agents openai anthropic

LlamaIndex — Data Framework for LLMs

Build RAG pipelines and LLM-powered data applications with LlamaIndex. Covers document loading, indexing, query engines, custom LLMs and embeddings, persistent storage, and agents.
python llamaindex llm rag ai embeddings agents retrieval

notebooklm-py — Unofficial NotebookLM Client

Automate Google NotebookLM from Python with the unofficial notebooklm-py library. Covers authentication, notebook and source management, summaries, FAQ generation, and audio podcast creation.
python notebooklm google ai automation unofficial

transformers — Hugging Face

Load and run pre-trained models for NLP, vision, and audio with the Hugging Face Transformers library. Covers pipelines, AutoModel, tokenisation, generation, fine-tuning, and device placement.
python huggingface transformers llm nlp ml pytorch

dagster — Modern Data Orchestration

Build, schedule, and observe data pipelines as software-defined assets with Dagster. Covers assets, jobs, schedules, sensors, resources, partitions, and the Dagster UI.
python dagster orchestration data pipelines assets etl mlops

DuckDB — Embedded Analytics Database

Run fast analytical SQL queries in-process with DuckDB. Covers Python API, CSV/Parquet ingestion, pandas interop, Arrow, window functions, and persistent databases.
python duckdb sql analytics olap parquet pandas arrow

litestar — High-Performance ASGI Framework

Build fast, type-safe HTTP APIs and web apps with Litestar. Covers route handlers, path/query/body params, DTOs, dependency injection, middleware, WebSockets, and OpenAPI.
python litestar asgi api web fastapi openapi rest

modin — Drop-in pandas at Scale

Speed up pandas workloads across all CPU cores with a one-line import swap. Covers Ray and Dask backends, config tuning, pandas interop, and when modin wins vs polars.
python modin pandas dataframes parallel ray dask data

polars — Fast DataFrames

High-performance DataFrames with a lazy expression API. Covers read/write, select, filter, group_by, joins, LazyFrame, datetime, string operations, and pandas interop.
python polars dataframes data csv parquet sql

prefect — Workflow Orchestration

Build, schedule, and observe Python workflows with Prefect. Covers flows, tasks, retries, schedules, deployments, caching, concurrency, and Prefect Cloud.
python prefect orchestration workflows scheduling etl pipelines

reflex — Full-Stack Web Apps in Pure Python

Build interactive web applications entirely in Python with Reflex. Covers state, components, events, pages, database, forms, and deployment.
python reflex web fullstack react ui components state

SQLModel — Typed ORM for FastAPI

Define database models with Python type hints using SQLModel. Covers table creation, CRUD, relationships, FastAPI integration, Pydantic validation, and async sessions.
python sqlmodel orm sql fastapi pydantic sqlalchemy database

tqdm — Progress Bars

Add auto-updating progress bars to any Python loop or CLI pipeline with tqdm. Covers iterables, manual updates, pandas integration, nested bars, async, Jupyter, and byte-piping.
python tqdm progress cli jupyter async

typer — CLI Apps with Type Hints

Build command-line interfaces using Python type annotations with Typer. Covers commands, options, arguments, subcommands, callbacks, rich output, and testing.
python typer cli argparse click terminal

JavaScript

Node.js runtime, package managers, async patterns, array methods, and frontend tooling — a complete JavaScript reference for the command line and the browser.
javascript node npm cli

Array Methods

JavaScript arrays have ~30 built-in methods for transforming, searching, and reducing data. Covers mutation, non-mutation, search, boolean, iteration, and static methods with real examples.
javascript arrays language

Async / Await

async/await syntax, error handling, parallel execution with Promise.all, sequential vs parallel loops, top-level await, AbortController, and common mistakes.
javascript async promises language

Error Handling

JavaScript error handling with try/catch/finally, built-in error types, custom error classes, error chaining with cause (ES2022), async errors, and practical patterns like result objects.
javascript errors language

Fetch API

The browser and Node 18+ built-in HTTP client that returns Promises. Covers GET/POST/PUT/DELETE, headers, error handling, streaming, AbortController, uploads, credentials, and CORS.
javascript fetch http api language

JavaScript Modules

CommonJS vs ES Modules in Node.js — syntax, how Node chooses the module system, dynamic import, top-level await, CJS/ESM interop, and common pitfalls.
javascript modules esm commonjs node

Node.js Runtime

How to use the Node.js runtime — REPL, running scripts, CLI flags, ESM vs CJS modules, built-in node: modules, the process object, and modern globals like fetch and structuredClone.
javascript node runtime cli esm cjs modules

Promises

JavaScript Promises represent the eventual completion or failure of an async operation. Covers states, chaining, combinators, callback conversion, AbortController, and common anti-patterns.
javascript promises async language

Regular Expressions

JavaScript has built-in RegExp support (ES2018+ with named groups, lookbehind, dotAll). Covers literal syntax, flags, character classes, methods, named captures, and common patterns.
javascript regex language

Programming

A reference hub for programming languages and their ecosystems — Python, JavaScript, and TypeScript, with package managers, runtimes, and tooling.
programming python javascript typescript overview

pip — Python Package Installer

Complete pip reference covering installation, package management, requirements files, private registries, caching, offline installs, and reproducible builds.
python pip packages cli packaging

TypeScript

Static typing for JavaScript — tsconfig reference, the full type system, generics, utility types, narrowing, and common compiler errors explained.
typescript javascript types

Common TypeScript Errors

A reference for the most frequent TypeScript compiler errors — their meaning, a minimal reproduction, and the correct fix. Covers TS2304, TS2345, TS2339, TS2322, TS2532, TS2554, TS2307, TS2366, TS7006, TS2571, TS2769, TS2693, plus type assertions and ts-expect-error.
typescript errors debugging language

Decorators

TypeScript decorators annotate and transform classes and class members. Covers the TC39 stage-3 standard decorators (TS 5.0+), legacy experimentalDecorators, decorator factories, method/class/field decorators, and reflect-metadata for NestJS and Angular patterns.
typescript decorators language

Enums

TypeScript enums create named constant sets as real runtime objects. Covers numeric, string, and const enums; reverse mapping; enum pitfalls; and when to prefer a union of string literals instead.
typescript enums language

Generics

TypeScript generics allow writing reusable, type-safe code that works over many types. Covers generic functions, interfaces, classes, constraints, keyof, conditional types, and the infer keyword.
typescript generics language

Mapped & Conditional Types

Mapped types iterate over type keys to create new types; conditional types pick between types based on a condition. Together they power all built-in utility types and advanced type composition.
typescript mapped-types conditional-types language

Type Narrowing

TypeScript narrowing refines broad types to specific ones within code branches. Covers typeof, instanceof, in, equality, assignment narrowing, discriminated unions, control flow analysis, and the never type.
typescript narrowing type-guards language

Type Guards

User-defined type guards narrow types at runtime using the `is` predicate, assertion functions, generic guards, and class-based patterns. Covers API validation, DOM guards, and when to use Zod.
typescript type-guards narrowing language

Type-Only Imports & Exports

import type and export type erase at compile time, preventing runtime side-effects and enabling better tree-shaking. Covers inline type qualifiers, verbatimModuleSyntax, and common gotchas with enums and namespaces.
typescript imports modules language

Types vs Interfaces

TypeScript has two ways to define object shapes — type aliases and interface declarations. Learn when each is appropriate, how they differ in extension, merging, and composability.
typescript types interfaces language

Utility Types

TypeScript's built-in generic utility types that transform existing types into new ones. Covers Partial, Required, Readonly, Record, Pick, Omit, Exclude, Extract, ReturnType, Awaited, and more.
typescript utility-types language

Python

Installation guides, essential packages, CLI snippets, and real-world recipes for Python 3.
python overview

asyncio — Async I/O

Write concurrent Python code with asyncio. Covers coroutines, asyncio.run, gather, create_task, timeouts, queues, and avoiding the blocking-call pitfall.
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black — Python Code Formatter

Format Python code consistently with black. Covers installation, configuration, editor integration, and how it compares to ruff format.
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Python CLI Snippets

Short standalone Python scripts for common tasks — file I/O, JSON manipulation, HTTP requests, CSV processing, and data transformation.
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click — CLI Builder

Build command-line interfaces with click using decorators. Covers commands, options, arguments, groups, prompts, and progress bars.
python click cli argparse terminal commands

django — Full-Stack Web Framework

Build database-driven web applications with Django. Covers project setup, models, migrations, the admin panel, views, forms, class-based views, middleware, signals, ORM advanced patterns, and the management command workflow.
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jupyter — Interactive Notebooks

Run interactive Python notebooks with Jupyter. Covers JupyterLab setup, cell types, keyboard shortcuts, magic commands, nbconvert export, and common pitfalls.
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loguru — Structured Logging

Add structured, colorized logging to Python apps with loguru. Covers sinks, log levels, file rotation, retention, exception catching, and context binding.
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matplotlib — Plotting

Create publication-quality 2-D plots with matplotlib. Covers pyplot basics, subplots, savefig, common chart types, and the show-vs-save pitfall.
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mypy — Static Type Checker

Catch type errors before runtime with mypy. Covers strict mode, common error codes, type: ignore annotations, gradual typing, and pyproject.toml configuration.
python mypy typing types static-analysis type-hints

numpy — Numerical Arrays

Create and manipulate N-dimensional arrays with NumPy. Covers array creation, broadcasting, vectorized math, indexing, and matrix operations.
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Python One-Liners

Useful Python one-liners runnable directly from the shell with python -c or python -m. No file creation needed.
python oneliners cli shell snippets

pandas — DataFrames

Load, filter, transform, and aggregate tabular data with pandas. Covers DataFrame creation, read_csv, groupby, merge, and the SettingWithCopy pitfall.
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pathlib — Object-Oriented File Paths

Work with filesystem paths using Python's built-in pathlib module. Covers Path creation, navigation, reading/writing files, glob patterns, and stat.
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Pillow — Image Processing

Open, resize, crop, convert, and save images with Pillow (PIL fork). Covers format conversion, filters, drawing, and EXIF handling.
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pytest — Testing Framework

Write and run Python tests with pytest. Covers test discovery, assertions, fixtures, parametrize, conftest, and common patterns.
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rich — Beautiful Terminal Output

Make terminal output beautiful with Rich. Covers styled print, Console, tables, progress bars, syntax highlighting, live displays, and the rich-cli command.
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ruff — Fast Linter & Formatter

Lint and format Python code with ruff — a single Rust-powered tool that replaces flake8, isort, and black. Covers configuration, rule selection, and CI usage.
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scipy — Scientific Computing

Statistical distributions, optimization, integration, signal processing, and linear algebra with SciPy. Builds on NumPy arrays.
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sqlalchemy — SQL Toolkit & ORM

Connect to databases, write queries, and define ORM models with SQLAlchemy 2.0. Covers the engine, sessions, Core queries, ORM declarative models, relationships, session lifecycle, migrations with Alembic, and connection pool configuration.
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