Release Notes 2025 Work - Python 3.13

Most pure‑Python code runs unchanged. The JIT and no‑GIL build are at runtime via environment variables ( PYTHONJIT=1 , PYTHON_NOGIL=1 ). Projects using C extensions should test thoroughly.

After experimental builds in 3.12 and 3.13 beta, the is now standard. Loop-heavy code (think data processing, numerical simulations) sees 20–40% speedups without any changes. The JIT works best on x86-64 and ARM64; WebAssembly and some embedded builds fall back to the bytecode interpreter. python 3.13 release notes 2025