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