---
id: librt
version: "0.15.0"
license: MIT
license_treatment: permissive
maintenance: active
---

# librt — Mypyc runtime library

License: permissive · Maintenance: active · Popularity: top 1,000 on PyPI

## Install

pip install librt
uv add librt
poetry add librt

## Description

# librt: mypyc runtime library

[![Stable Version](https://img.shields.io/pypi/v/librt?color=blue)](https://pypi.org/project/librt/)
[![Downloads](https://img.shields.io/pypi/dm/librt)](https://pypistats.org/packages/librt)
[![Build Status](https://github.com/mypyc/librt/actions/workflows/buildwheels.yml/badge.svg)](https://github.com/mypyc/librt/actions)
[![Checked with mypy](https://www.mypy-lang.org/static/mypy_badge.svg)](https://mypy-lang.org/)

This library contains basic functionality that is useful in code compiled
using the [mypyc](https://mypyc.readthedocs.io/en/latest/) compiler, and efficient
C alternatives to various Python standard library classes and functions. Mypyc can
produce faster extensions when you use `librt` in the code you compile. `librt` also
contains some internal library features used by mypy.

Here are some feature highlights:

 * [librt.vecs](https://mypyc.readthedocs.io/en/latest/librt_vecs.html) defines the growable packed array-like type `vec`
 * [librt.strings](https://mypyc.readthedocs.io/en/latest/librt_strings.html) defines fast string and bytes builders and binary data read/write helpers
 *...

## AI interpretation — verify before relying

librt provides optimized C implementations of runtime utilities for code compiled with mypyc, including growable arrays, fast string/bytes builders, and SIMD-accelerated Base64 encoding.

Verdict: librt is an actively maintained, permissively licensed runtime library for mypyc-compiled code with no known vulnerabilities. Its medium install friction stems from extensive platform-specific wheels rather than dependency complexity. Suitable for projects using mypyc or mypy, though PyPy users should note explicit non-support.

[View on SkillFed](https://skillfed.io/packages/librt) · [View on PyPI](https://pypi.org/project/librt/)