Python 3.15.0 Release Candidate 2: Final Preview Before October GA

Python 3.15.0 Release Candidate 2, the final preview before general availability on October 1, 2026, has been released. This candidate includes approximately 144 bugfixes and build improvements since its predecessor, with no further ABI changes planned. It introduces significant enhancements such as explicit lazy imports, new `frozendict` and `sentinel` built-in types, and an upgraded JIT compiler offering 8-13% performance boosts. Third-party project maintainers are encouraged to use this phase for testing and publishing Python 3.15 wheels to ensure ecosystem readiness.