Mypyc runtime library that provides basic functionality and efficient C alternatives to various Python standard library classes and functions for code compiled with the mypyc compiler. It is useful for speeding up mypyc-generated extensions, and it also includes internal features used by mypy.
Project status
- Actively maintained: The repo shows very recent activity (latest upstream push and the newest update, v0.16.0, on 2026-09-28), suggesting ongoing maintenance rather than a dormant state.
- Update cadence: There are multiple updates in 2026, including back-to-back releases around 2026-08-06 to 2026-08-07 (v0.14.0 then v0.15.0), followed by another update about 7 weeks later (v0.16.0 on 2026-09-28).
AI summary generated
Recent updates
v0.16.0
v0.16.0 makes substantial internal runtime changes in lib-rt, focused on module import synchronization, faster/safer free-threaded attribute reads, and related low-level helpers. Release notes were not provided, so the changes below are effectively undocumented.
Featuresv0.15.0
Release v0.15.0 contains build and platform expansion changes and a small internal runtime change in the C code. No release notes were provided by the publisher, so the actual behavior changes are inferred from the code diff.
BreakingFeaturesv0.14.0
Version v0.14.0 was published on 2026-08-06, but the publisher did not include any release notes. As a result, there is no documented information here about new features, breaking changes, bug fixes, security, performance, or migration steps.
v0.13.0
v0.13.0 includes substantial internal runtime changes to improve correctness and performance for free-threaded (Py_GIL_DISABLED) builds, especially around list access and iteration. It also adds a new C extension module, `librt.threading`, exposing a `Lock` type with an accompanying `.pyi` stub. No release notes were provided by the publisher.
Featuresv0.12.0
v0.12.0 includes changes to the build and release pipeline (cibuildwheel upgrade and removal of a WASM wheel skipping step), plus multiple runtime updates focused on free-threaded (Py_GIL_DISABLED) safety in the mypyc runtime library. It also adds new string/codepoint helper functions (isspace, isdigit, isalnum, isalpha, isidentifier, toupper, tolower) to the librt.strings module and corresponding .pyi typings.
BreakingFeaturesv0.11.0
v0.11.0 introduces a new native module, librt.random, including a C implementation of a ChaCha8-based PRNG and Python bindings. In addition, it makes significant internal changes to librt.vecs, including a redesigned C-level data layout and new strict ABI/API versioning for the vecs C API. There were no release notes provided, so these changes are effectively undocumented by the publisher.
BreakingFeaturesv0.10.0
The v0.10.0 release has no publisher-provided release notes. The code diff shows multiple internal runtime changes, including module bootstrap logic, C capsule API loading refactors, and altered base64 decoding behavior.
Breakingv0.9.0
Release v0.9.0 updates the mypyc runtime with new string and import utilities, plus enhanced functionality for the specialized vec container types (iteration and containment). It also introduces a new internal runtime API surface (via a capsule) and changes the class construction flow so __init_subclass__ is no longer triggered directly inside CPyType_FromTemplate.
BreakingFeaturesv0.8.1
v0.8.1 has no publisher-provided release notes. The code diff indicates this release focuses on how the project builds CPU-specific Base64 decoding routines (AVX, AVX2, AVX512, SSE4.x, SSSE3) for GCC and Clang, plus a small change to symbol export configuration for the Python extension entrypoint.
v0.8.0
Release v0.8.0 was published on 2026-02-12, but no release notes were provided by the publisher. As a result, there is no documented information here about new features, breaking changes, bug fixes, security fixes, or migration steps, and developers should review the actual diff and changelog in the repository before upgrading.