Python 3.15 arrives with lazy imports and new built-in types

Python 3.15 has been released with several major language and tooling updates. The release adds lazy imports, a frozendict immutable dictionary type, and a sentinel() helper for unique marker objects. It also introduces a statistical sampling profiler intended to reduce profiling overhead compared with cProfile.

Python 3.15's release adds several long-requested capabilities. Imports can now be deferred until a module is actually needed, and existing conventional imports can be made to work this way through configuration or an environment setting. A new immutable, hashable dictionary variant, frozendict, joins the built-in types, while sentinel("NAME") creates distinct marker objects with useful representations and type-checking support.

A new profiling.sampling module uses statistical sampling to lower overhead compared with deterministic cProfile, now also called profiling.tracing. CPython's JIT, introduced in 3.13, gains a new tracing front end, register allocation, improved generated machine code, and other optimizations, yielding reported geometric mean speedups of 8% to 13% depending on platform and workload.