beartype

Unbearably fast near-real-time pure-Python runtime-static type-checker.

beartype Permissive license MIT License Copyright (c) 2014-2025 Beartype authors. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the… (full text in the JSON record) Active ★ 3,483 v0.22.9 released 2025-12-13

Install

beartype on PyPI

pip

pip install beartype

uv

uv add beartype

poetry

poetry add beartype

Package facts

License	MIT License Copyright (c) 2014-2025 Beartype authors. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the… (full text in the JSON record) (permissive)
Python support	supports the current Python release (>=3.10)
Install friction	low — pure-Python wheel
Runtime dependencies	none
Maintenance	actively maintained — 243 days since the last release
Last repo commit	2026-08-13
First released	2020-05-21
Popularity	one of the top 1,000 most-downloaded packages on PyPI (30-day window, as of 2026-08-13)
Known vulnerabilities	none known (OSV.dev, checked 2026-08-13)

Evidence: beartype-0.22.9-py3-none-any.whl

Keywords: annotations, python, type checking, type hints

Development Status :: 5 - Production/StableIntended Audience :: DevelopersLicense :: OSI Approved :: MIT LicenseNatural Language :: EnglishOperating System :: OS IndependentProgramming Language :: Python :: 3Programming Language :: Python :: 3 :: OnlyTopic :: Software Development :: Code GeneratorsTopic :: Software Development :: Libraries :: Python ModulesTopic :: Software Development :: Quality AssuranceTyping :: Typed

About beartype

from the package's own PyPI description — quoted content, verbatim

.. # ------------------( LICENSE )------------------ .. # Copyright (c) 2014-2025 Beartype authors. .. # See "LICENSE" for further details. .. # .. # ------------------( SEO )------------------ .. # Metadata converted into HTML-specific meta tags parsed by search engines. .. # Note that: .. # * The "description" should be no more than 300 characters and ideally no .. # more than 150 characters, as search engines may silently truncate this .. # description to 150 characters in edge cases.

.. meta:: :description lang=en: Beartype is an open-source pure-Python PEP-compliant constant-time runtime type checker emphasizing efficiency and portability.

.. # ------------------( SYNOPSIS )------------------

================= |beartype-banner| =================

⚠

`Beartype documentation lives at ReadTheDocs (RTD) &lt;beartype RTD_&gt;`__. It's
readable, structured, and soothing to the deep folds of your big galactic
brain. Open your mind to an ocean of mundane knowledge that will exhaust
you at work. Enter... **the...

Read as markdown · JSON record · Source repository · Docs

AI interpretation — verify before relying

AI-generated interpretation of the package facts above; every digit, version, license, or vulnerability id it cites is grounded in the facts already shown on this page

Beartype is a pure-Python runtime type checker that validates type hints on functions, classes, and variable assignments with minimal performance overhead, supporting PEP-compliant annotations and custom validators.

Beartype has zero runtime dependencies and installs as a pure-Python wheel with low friction. The project is actively maintained with a recent release 243 days ago and strong community engagement (3483 GitHub stars), indicating reliable ongoing support.

Beartype is licensed under the MIT License, a permissive open-source license that allows unrestricted use, modification, and distribution in both commercial and private projects with minimal obligations beyond attribution.

Usage

pip install beartype

from beartype import beartype

@beartype
def greet(name: str) -> str:
    return f"Hello, {name}!"

greet("World")  # Valid call
greet(b"bytes")  # Raises BeartypeCallHintParamViolation

Requires Python 3.10 or later.

Verdict: Beartype is a production-ready, actively maintained type checker with zero dependencies, permissive MIT licensing, and no known vulnerabilities. Its low install friction and strong maintenance signal make it a reliable choice for runtime type validation in Python 3.10+ projects.

Needs verification

Performance overhead characteristics compared to static type checkers or other runtime validators in typical application scenarios.
Compatibility with dynamic typing patterns or type-checking frameworks beyond standard PEP annotations.
Real-world adoption patterns and integration success in large codebases.

runtime type checking pythontype hint validation decoratorpython type annotations enforcerfast runtime type validationbeartype type checkingpython type safety enforcementpep compliant type checker