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),exceptwithout bracketsreferences/new-modules.md—compression.zstd,functools.Placeholder,copy.replace(),warnings.deprecated(),locals()semantics, remote debugging,io.Reader/Writer,uuid.uuid7(),heapqmax-heapreferences/concurrency.md— Free-threaded CPython (GIL-free mode), subinterpreters,InterpreterPoolExecutorreferences/removals.md— Dead batteries (19 modules), 3.13/3.14 removals, breaking behavior changes