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Python

62 cheat sheets

Python#

A practical reference for Python 3 — from first install to production-ready packages.

What’s in this section#

TopicPages
InstallationPer-OS install guides with verification steps
Virtual environmentsvenv setup, activation, and management
Essential packages34 packages with examples, pitfalls, and output samples
CLI snippetsOne-liners and small standalone scripts
RichTerminal formatting, tables, progress bars, and live output
  1. Installation — pick your OS
  2. Virtual environments — always use one
  3. Essential packages — browse the catalogue
  4. CLI snippets and scripts
  5. Rich — make terminal output beautiful

[!TIP] All code blocks on every page have a one-click copy button. Output samples are shown in plain text blocks directly below each example so you can see exactly what to expect.

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.

May 25, 2026
python install

Python Installation — Windows

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

May 25, 2026
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.

May 25, 2026
python install wsl ubuntu linux

Python Installation — macOS

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

May 25, 2026
python install macos homebrew pyenv

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.

May 25, 2026
python install linux debian ubuntu fedora arch pyenv

Virtual Environments — venv

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

May 25, 2026
python venv virtualenv pip packaging

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.

May 25, 2026
python packaging pyproject toml build pep-621

pip — Python Package Installer

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

Apr 26, 2026
python pip packages cli packaging

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.

May 25, 2026
python packages pip overview

requests — HTTP for Humans

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

May 25, 2026
python requests http api networking

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.

May 25, 2026
python httpx http api async networking

numpy — Numerical Arrays

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

Apr 25, 2026
python numpy arrays math data scientific

pandas — DataFrames

Load, filter, transform, and aggregate tabular data with pandas. Covers DataFrame creation, read_csv, groupby, merge, and the SettingWithCopy pitfall.

Apr 25, 2026
python pandas dataframes data csv analysis

matplotlib — Plotting

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

Apr 25, 2026
python matplotlib plotting visualization charts graphs

scipy — Scientific Computing

Statistical distributions, optimization, integration, signal processing, and linear algebra with SciPy. Builds on NumPy arrays.

Apr 25, 2026
python scipy statistics optimization scientific math

Pillow — Image Processing

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

Apr 25, 2026
python pillow pil images imaging graphics

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.

May 25, 2026
python scikit-learn ml data-science pipelines modeling classification

click — CLI Builder

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

Apr 25, 2026
python click cli argparse terminal commands

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.

May 25, 2026
python pydantic validation types models serialization

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.

Apr 25, 2026
python sqlalchemy orm sql database sqlite postgres

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.

May 25, 2026
python flask web api wsgi microframework

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.

Apr 25, 2026
python django web orm wsgi framework admin

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.

May 25, 2026
python fastapi api async asgi rest openapi pydantic

pytest — Testing Framework

Write and run Python tests with pytest. Covers test discovery, assertions, fixtures, parametrize, conftest, and common patterns.

Apr 25, 2026
python pytest testing fixtures parametrize tdd

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.

Apr 25, 2026
python mypy typing types static-analysis type-hints

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.

Apr 25, 2026
python ruff linting formatting code-quality tools

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.

May 25, 2026
python typing types stdlib mypy generics protocol

black — Python Code Formatter

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

Apr 25, 2026
python black formatting code-quality tools

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.

May 25, 2026
python pdb debugging stdlib repl tooling

BeautifulSoup — HTML Parsing & Scraping

Parse, search, and mutate HTML/XML with BeautifulSoup 4. Covers parser choice (html.parser/lxml/html5lib), find/find_all/select, tree navigation, attribute access, and pairing with requests/httpx/playwright for end-to-end scraping.

May 25, 2026
python beautifulsoup scraping html parsing web

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.

May 25, 2026
python pre-commit git-hooks workflow ci code-quality tooling

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.

May 25, 2026
python uv pip packaging venv tools astral

poetry — Dependency Management & Packaging

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

May 25, 2026
python poetry packaging dependencies pyproject lockfile

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.

May 25, 2026
python stdlib cli scripting tooling

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.

Apr 25, 2026
python asyncio async await concurrency coroutines

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.

May 25, 2026
python stdlib time timezones parsing data

logging — Stdlib Logging

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

May 25, 2026
python stdlib logging

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.

Apr 25, 2026
python pathlib files filesystem stdlib paths

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.

May 25, 2026
python stdlib json data serialization parsing

loguru — Structured Logging

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

Apr 25, 2026
python loguru logging debugging structured-logging

jupyter — Interactive Notebooks

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

Apr 25, 2026
python jupyter notebooks data analysis interactive

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.

May 25, 2026
python stdlib shell

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.

May 25, 2026
python stdlib typing

prefect — Workflow Orchestration

Build, schedule, and observe Python workflows with Prefect. Covers flows, tasks, retries, schedules, deployments, caching, concurrency, and Prefect Cloud.

Apr 27, 2026
python prefect orchestration workflows scheduling etl pipelines

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.

May 25, 2026
python streamlit ui dataviz prototyping web frontend

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.

Apr 27, 2026
python litestar asgi api web fastapi openapi rest

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.

Apr 27, 2026
python reflex web fullstack react ui components state

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.

Apr 27, 2026
python tqdm progress cli jupyter async

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.

Apr 27, 2026
python polars dataframes data csv parquet sql

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.

Apr 27, 2026
python modin pandas dataframes parallel ray dask data

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).

May 25, 2026
python stdlib functional itertools functools

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.

Apr 27, 2026
python typer cli argparse click terminal

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.

Apr 27, 2026
python sqlmodel orm sql fastapi pydantic sqlalchemy database

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.

Apr 27, 2026
python duckdb sql analytics olap parquet pandas arrow

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.

May 25, 2026
python stdlib regex re patterns

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.

Apr 27, 2026
python dagster orchestration data pipelines assets etl mlops

Python One-Liners

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

Apr 25, 2026
python oneliners cli shell snippets

Python CLI Snippets

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

Apr 25, 2026
python snippets cli scripts json csv http file-io

AWS CLI — Command-Line Interface for Amazon Web Services

Drive every AWS service from a terminal. Covers install (pip vs v2 installer), aws configure, profiles, SSO, day-to-day commands across S3 / EC2 / Lambda / IAM / STS, common scenarios, and credential precedence.

May 31, 2026
python aws cloud cli sdk

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.

Apr 25, 2026
python rich terminal tui cli colors progress tables

pip vs uv — Package Manager Comparison

Side-by-side feature comparison of pip and uv — speed, lock files, virtual envs, Python version management, and when to use each.

May 25, 2026
python package-management pip uv

pygmentize — Syntax highlighter CLI from Pygments

Highlight source code from the command line — many lexers, many output formats.

May 31, 2026
cli pygments syntax-highlighting formatting