Python 3.13+ Knowledge Patch

Claude's baseline knowledge covers Python through 3.12. This skill provides features from 3.13 (Oct 2024) onwards.

Source: Python "What's New" documentation at https://docs.python.org/3/whatsnew/

3.13 Breaking Changes

Change Impact

19 "dead battery" modules removed (PEP 594) ImportError for cgi , crypt , imghdr , telnetlib , etc. See removals

locals() returns snapshots in functions (PEP 667) exec() /eval() in functions need explicit namespace. See new-modules

TypedDict("T", x=int) keyword syntax removed Use class syntax or TypedDict("T", {"x": int})

pathlib.Path.glob("") returns files AND dirs Add trailing / for dirs only: glob("/")

Docstring leading whitespace stripped May affect doctest tests

3.13 New Features

Feature Quick reference

Free-threaded CPython (PEP 703) python3.13t , sys._is_gil_enabled() , PYTHON_GIL=0 . See concurrency

copy.replace() protocol copy.replace(obj, field=val) , implement replace() . See new-modules

warnings.deprecated() (PEP 702) @deprecated("msg") — runtime warning + type checker signal. See new-modules

3.14 New Syntax

Feature Quick reference

T-strings (PEP 750) t"Hello {name}" → Template object. from string.templatelib import Template, Interpolation . See new-syntax

Deferred annotations (PEP 649/749) Forward refs no longer need quotes. from annotationlib import get_annotations, Format . See new-syntax

except without brackets (PEP 758) except A, B: (no parens, no as ). Parens still needed with as .

3.14 New Modules

Module Quick reference

compression.zstd (PEP 784) from compression import zstd; zstd.compress(data) . See new-modules

concurrent.interpreters (PEP 734) Subinterpreters + InterpreterPoolExecutor . See concurrency

annotationlib

get_annotations(obj, format=Format.FORWARDREF)

functools.Placeholder

partial(func, Placeholder, fixed_arg) — reserve positional slots

3.14 Breaking Changes

Change Impact

asyncio.get_event_loop() raises RuntimeError

Must use asyncio.run() or asyncio.Runner

multiprocessing default → 'forkserver' on Linux May cause pickling errors; use get_context('fork')

int() no longer uses trunc()

Must implement int() or index()

functools.partial is method descriptor Wrap in staticmethod() for classes

from future import annotations deprecated Unchanged behavior; removal after 2029

ast.Num /Str /Bytes removed Use ast.Constant

asyncio child watcher classes removed Use asyncio.run()

SyntaxWarning in finally (PEP 765) return /break /continue in finally now warns

3.14 New APIs

API Quick reference

sys.remote_exec(pid, script) (PEP 768) Attach debugger to running process; python -m pdb -p PID . See new-modules

io.Reader / io.Writer

Simpler protocol alternatives to typing.IO

uuid.uuid7()

Time-ordered UUID (RFC 9562); also uuid6() , uuid8()

heapq.*_max()

heapify_max() , heappush_max() , heappop_max() , etc.

Free-threading (PEP 779) Now officially supported; 5-10% overhead

Reference Files

For detailed patterns, code examples, and migration guidance, consult:

• references/new-syntax.md — T-strings (template processors, API), deferred annotations (annotationlib ), except without brackets

• references/new-modules.md — compression.zstd , functools.Placeholder , copy.replace() , warnings.deprecated() , locals() semantics, remote debugging, io.Reader /Writer , uuid.uuid7() , heapq max-heap

• references/concurrency.md — Free-threaded CPython (GIL-free mode), subinterpreters, InterpreterPoolExecutor

• references/removals.md — Dead batteries (19 modules), 3.13/3.14 removals, breaking behavior changes