CPython Rust Proposal Targets Memory Safety, Starting With Optional zlib Implementation

The Rust for CPython project proposes adding Rust to Python’s standard interpreter to improve memory safety, initially through selected standard-library modules. The roadmap calls for an optional Rust implementation of the zlib module in Python 3.16, scheduled for October 2027 under the release schedule documented in PEP 826, followed by a mandatory Rust requirement for Python 3.18 in 2029. A formal Python Enhancement Proposal is expected by the end of 2026; adoption remains subject to Steering Council approval and predefined developer-support, performance, and platform-compatibility criteria.

The proposal raises portability concerns and questions about the security-maintenance burden of Cargo dependencies. The team proposes minimizing dependencies and bundling their source code so CPython can be built without Cargo. For organizations maintaining Python runtimes, the planned transition would warrant tracking build-toolchain requirements, supported platforms, and dependency-management changes, but the roadmap is not yet an approved CPython commitment.