New features in Python 3.13 and 3.14

Python 3.13, released in 2024, introduced an experimental free-threaded build without the GIL via PEP 703, an experimental JIT compiler, an improved interactive REPL with multi-line editing and color, the new typing.TypeIs construct, and deprecation cleanups. It set the stage for the major improvements in 3.14.

The new REPL is a complete rewrite based on PyPy's REPL, with built-in multi-line editing, paste mode, command history that persists across sessions, syntax highlighting, and helpful exit messages. It dramatically improves the interactive experience compared to the old line-based REPL.

Python 3.14, released October 2025, adds template strings via PEP 750, the concurrent.interpreters module for subinterpreters via PEP 734, official support for free-threaded builds, a safe external debugger interface via PEP 768, deferred annotations via PEP 649, and many smaller improvements and standard library additions.

PEP 649 changes how type annotations are evaluated, deferring them by default to avoid the overhead of evaluating annotations at function definition time and to allow forward references without quoting. Annotations become accessible as proxies that evaluate lazily, removing the long-standing need for string-quoted forward references in many cases.

PEP 734 adds the concurrent.interpreters module, providing a high-level Python API for subinterpreters that landed in 3.14. Subinterpreters allow multiple isolated Python interpreters within a single process, each with its own state. Combined with per-interpreter GILs, this enables a new model of parallelism without the overhead of multiprocessing.

Threads share memory and the GIL within a single interpreter. Subinterpreters have isolated state, including modules, classes, and exceptions, and each has its own GIL. They communicate through explicit channels, not shared variables. Subinterpreters offer process-like isolation with thread-like overhead.

Recent versions added the new generic syntax via PEP 695 in 3.12, the typing.override decorator for explicit method overriding, typing.TypeIs for type narrowing with stricter semantics than TypeGuard, ReadOnly for TypedDict fields, and many improvements to the type system to align with what type checkers already support.

PEP 750 introduces template string literals, called t-strings, in Python 3.14. A t-string looks like an f-string with a t prefix but produces a Template object instead of a finished string. The Template exposes static parts and interpolations, letting libraries process them safely for SQL queries, HTML output, shell commands, and other contexts where escaping matters. ---