Python 3.15.0 final adds lazy imports, frozendict and UTF-8 as the default encoding

The stable release also upgrades the experimental JIT and adds a sampling profiler to the standard library.

Python 3.15.0 is now available as a stable release, according to the Python Insider blog. The release draws on more than five thousand commits from over a thousand contributors.

Language and interpreter changes include explicit lazy imports for faster startup, a new frozendict built-in type, a sentinel built-in type, unpacking in comprehensions, and UTF-8 as the default encoding. The experimental JIT compiler has been upgraded, with the team reporting a geometric mean gain of 7-8% on x86-64 Linux and 11-12% on AArch64 macOS.

The standard library gains a dedicated profiling package and Tachyon, a high-frequency statistical sampling profiler. Typing additions include TypedDict with typed extra items and a way to annotate type forms.

The official macOS binaries now install free-threading support by default, and the official Windows 64-bit binaries use the tail-calling interpreter. The post also warns that tkinter applications such as IDLE may hang on macOS 27.0, so teams relying on Tk there should test before upgrading the operating system. Developers should review the What's New document and run their test suites on 3.15 before moving production workloads.

Sources

• Python 3.15.0 (final) is here!official

Verified Oct 23, 2026 (official source). pythondeveloper-toolsreleaseprogramming-languages