fable-library

Fable library for Python

fable-library v5.13.0 139.6K downloads/30d#11,297 on PyPI

Permissive license MIT Active released 2026-07-24

What it is and what it does

Fable Library for Python is the runtime foundation for F# code compiled to Python via the Fable compiler. It bridges the gap between F# semantics and Python execution by providing type definitions, runtime utilities, and Rust-based extensions for features like unsigned integers that Python doesn't natively support. The library uses a two-tier architecture combining Python components for core functionality with Rust extensions for performance and proper type representation.

The package is distributed as pre-built wheels across multiple platforms and architectures, making it straightforward to install as a dependency. Library authors can choose between bundling it with their compiled code or declaring it as a PyPI dependency; the PyPI approach is required for libraries intended for distribution beyond a single machine.

Use it for:

Running F# libraries compiled to Python that depend on unsigned integer types
Distributing cross-platform F# code as Python packages with proper type support
Integrating F# and Python codebases where F# components are compiled to Python
Accessing performance-critical Rust implementations for operations not efficiently done in pure Python

Worth the install?

AI-flagged interpretation of the facts on this page — verify before relying

Fable Library for Python provides runtime support and type definitions for F# code compiled to Python, including Rust-based extensions for unsigned integer types and performance-critical operations.

Yes, if you are using F# code compiled to Python via Fable. It is a required runtime dependency for such projects and is actively maintained with no known vulnerabilities. The MIT license and broad platform support make it a straightforward addition. If you are not using Fable-compiled F# code, there is no reason to install it.

Install

fable-library on PyPI

pip

pip install fable-library

uv

uv add fable-library

poetry

poetry add fable-library

Installing fable-library

Before you install

Medium install friction due to compiled Rust extensions across multiple platforms, but wheels are pre-built for all major architectures. Actively maintained with a release 21 days ago.

License in practice

MIT license permits unrestricted use, modification, and distribution in both open-source and commercial projects.

Quickstart

pip install fable-library==5.13.0

import fable_library
# Use Fable-compiled F# code in Python

Requires Python 3.10 or later; Python 4.0 and above are not supported.

Verify before relying

What specific Rust extensions are included and what performance gains they provide
How to integrate Fable-compiled F# modules with this library
Whether the bundled vs. PyPI distribution choice affects runtime behavior

Package facts

License	MIT (permissive)
Python support	supports the current Python release (<4.0,>=3.10)
Install friction	medium — platform-specific wheel
Runtime dependencies	none
Maintenance	actively maintained — 21 days since the last release
First released	2021-01-21
Downloads	139,584/month — #11,297 on PyPI (30-day window, as of 2026-08-14)
Known vulnerabilities	none known (OSV.dev, checked 2026-08-14)

Evidence: fable_library-5.13.0-cp310-cp310-manylinux_2_17_aarch64.manylinux2014_aarch64.whl; fable_library-5.13.0-cp310-cp310-manylinux_2_17_armv7l.manylinux2014_armv7l.whl; fable_library-5.13.0-cp310-cp310-manylinux_2_17_ppc64le.manylinux2014_ppc64le.whl; fable_library-5.13.0-cp310-cp310-manylinux_2_17_s390x.manylinux2014_s390x.whl; fable_library-5.13.0-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl; fable_library-5.13.0-cp310-cp310-manylinux_2_5_i686.manylinux1_i686.whl; fable_library-5.13.0-cp310-cp310-musllinux_1_2_aarch64.whl; fable_library-5.13.0-cp310-cp310-musllinux_1_2_armv7l.whl; fable_library-5.13.0-cp310-cp310-musllinux_1_2_i686.whl; fable_library-5.13.0-cp310-cp310-musllinux_1_2_x86_64.whl; fable_library-5.13.0-cp310-cp310-win_amd64.whl; fable_library-5.13.0-cp311-cp311-macosx_10_12_x86_64.whl; fable_library-5.13.0-cp311-cp311-macosx_11_0_arm64.whl; fable_library-5.13.0-cp311-cp311-manylinux_2_17_aarch64.manylinux2014_aarch64.whl; fable_library-5.13.0-cp311-cp311-manylinux_2_17_armv7l.manylinux2014_armv7l.whl; fable_library-5.13.0-cp311-cp311-manylinux_2_17_ppc64le.manylinux2014_ppc64le.whl; fable_library-5.13.0-cp311-cp311-manylinux_2_17_s390x.manylinux2014_s390x.whl; fable_library-5.13.0-cp311-cp311-manylinux_2_17_x86_64.manylinux2014_x86_64.whl; fable_library-5.13.0-cp311-cp311-manylinux_2_5_i686.manylinux1_i686.whl; fable_library-5.13.0-cp311-cp311-musllinux_1_2_aarch64.whl