python · AA-Turner · Aug 15, 2025 · Aug 15, 2025 · Aug 15, 2025 · Aug 15, 2025
@@ -75,6 +75,7 @@ The debugger's prompt is ``(Pdb)``, which is the indicator that you are in debug
    arguments of the ``p`` command.
 
 
+.. _pdb-cli:
 .. program:: pdb
 
 You can also invoke :mod:`pdb` from the command line to debug other scripts.  For

@@ -1288,12 +1288,11 @@ asyncio
   :meth:`asyncio.TaskGroup.create_task`.
   (Contributed by Thomas Grainger in :gh:`128307`.)
 
-
-bdb
----
-
-* The :mod:`bdb` module now supports the :mod:`sys.monitoring` backend.
-  (Contributed by Tian Gao in :gh:`124533`.)
+* There are two new utility functions for
+  introspecting and printing a program's call graph:
+  :func:`~asyncio.capture_call_graph` and :func:`~asyncio.print_call_graph`.
+  (Contributed by Yury Selivanov, Pablo Galindo Salgado, and Łukasz Langa
+  in :gh:`91048`.)
 
 
   .. _whatsnew314-color-calendar:
@@ -1521,36 +1520,6 @@ functools
   (Contributed by Sayandip Dutta in :gh:`125916`.)
 
 
-gc
---
-
-The cyclic garbage collector is now incremental,
-which changes the meaning of the results of
-:meth:`~gc.get_threshold` and :meth:`~gc.set_threshold`
-as well as :meth:`~gc.get_count` and :meth:`~gc.get_stats`.
-
-* For backwards compatibility, :meth:`~gc.get_threshold` continues to return
-  a three-item tuple.
-  The first value is the threshold for young collections, as before;
-  the second value determines the rate at which the old collection is scanned
-  (the default is 10, and higher values mean that the old collection
-  is scanned more slowly).
-  The third value is meaningless and is always zero.
-
-* :meth:`~gc.set_threshold` ignores any items after the second.
-
-* :meth:`~gc.get_count` and :meth:`~gc.get_stats` continue to return
-  the same format of results.
-  The only difference is that instead of the results referring to
-  the young, aging and old generations,
-  the results refer to the young generation
-  and the aging and collecting spaces of the old generation.
-
-In summary, code that attempted to manipulate the behavior of the cycle GC
-may not work exactly as intended, but it is very unlikely to be harmful.
-All other code will work just fine.
-
-
 getopt
 ------
 
@@ -1919,13 +1888,6 @@ pdb
 * ``$_asynctask`` is added to access the current asyncio task if applicable.
   (Contributed by Tian Gao in :gh:`124367`.)
 
-* :mod:`pdb` now supports two backends: :func:`sys.settrace` and
-  :mod:`sys.monitoring`. Using :mod:`pdb` CLI or :func:`breakpoint` will
-  always use the :mod:`sys.monitoring` backend. Explicitly instantiating
-  :class:`pdb.Pdb` and its derived classes will use the :func:`sys.settrace`
-  backend by default, which is configurable.
-  (Contributed by Tian Gao in :gh:`124533`.)
-
 * :func:`pdb.set_trace_async` is added to support debugging asyncio
   coroutines. :keyword:`await` statements are supported with this
   function.
@@ -2266,14 +2228,16 @@ zipinfo
 
 .. Add improved modules above alphabetically, not here at the end.
 
+
 Optimizations
 =============
 
 * The import time for several standard library modules has been improved,
-  including :mod:`ast`, :mod:`asyncio`, :mod:`base64`, :mod:`cmd`, :mod:`csv`,
-  :mod:`gettext`, :mod:`importlib.util`, :mod:`locale`, :mod:`mimetypes`,
-  :mod:`optparse`, :mod:`pickle`, :mod:`pprint`, :mod:`pstats`, :mod:`socket`,
-  :mod:`subprocess`, :mod:`threading`, :mod:`tomllib`, and :mod:`zipfile`.
+  including :mod:`annotationlib`, :mod:`ast`, :mod:`asyncio`, :mod:`base64`,
+  :mod:`cmd`, :mod:`csv`, :mod:`gettext`, :mod:`importlib.util`, :mod:`locale`,
+  :mod:`mimetypes`, :mod:`optparse`, :mod:`pickle`, :mod:`pprint`,
+  :mod:`pstats`, :mod:`shlex`, :mod:`socket`, :mod:`string`, :mod:`subprocess`,
+  :mod:`threading`, :mod:`tomllib`, :mod:`types`, and :mod:`zipfile`.
 
   (Contributed by Adam Turner, Bénédikt Tran, Chris Markiewicz, Eli Schwartz,
   Hugo van Kemenade, Jelle Zijlstra, and others in :gh:`118761`.)
@@ -2282,32 +2246,44 @@ Optimizations
 asyncio
 -------
 
-* :mod:`asyncio` has a new per-thread double linked list implementation internally for
-  :class:`native tasks <asyncio.Task>` which speeds up execution by 10-20% on standard
-  pyperformance benchmarks and reduces memory usage.
+* Standard benchmark results have improved by 10-20%, following the
+  implementation of a new per-thread double linked list
+  for :class:`native tasks <asyncio.Task>`,
+  also reducing memory usage.
   This enables external introspection tools such as
   :ref:`python -m asyncio pstree <whatsnew314-asyncio-introspection>`
   to introspect the call graph of asyncio tasks running in all threads.
   (Contributed by Kumar Aditya in :gh:`107803`.)
 
-* :mod:`asyncio` has first class support for :term:`free-threading builds <free threading>`.
-  This enables parallel execution of multiple event loops across different threads and scales
-  linearly with the number of threads.
+* The module now has first class support for
+  :term:`free-threading builds <free threading>`.
+  This enables parallel execution of multiple event loops across
+  different threads, scaling linearly with the number of threads.
   (Contributed by Kumar Aditya in :gh:`128002`.)
 
-* :mod:`asyncio` has new utility functions for introspecting and printing
-  the program's call graph: :func:`asyncio.capture_call_graph` and
-  :func:`asyncio.print_call_graph`.
-  (Contributed by Yury Selivanov, Pablo Galindo Salgado, and Łukasz Langa
-  in :gh:`91048`.)
-
 
 base64
 ------
 
-* Improve the performance of :func:`base64.b16decode` by up to ten times,
-  and reduce the import time of :mod:`base64` by up to six times.
-  (Contributed by Bénédikt Tran, Chris Markiewicz, and Adam Turner in :gh:`118761`.)
+* :func:`~base64.b16decode` is now up to six times faster.
+  (Contributed by Bénédikt Tran, Chris Markiewicz, and Adam Turner
+  in :gh:`118761`.)
+
+
+bdb
+---
+
+* The basic debugger now has a :mod:`sys.monitoring`-based backend,
+  which can be selected via the passing ``'monitoring'``
+  to the :class:`~bdb.Bdb` class's new *backend* parameter.
+  (Contributed by Tian Gao in :gh:`124533`.)
+
+
+difflib
+-------
+
+* The :func:`~difflib.IS_LINE_JUNK` function is now up to twice as fast.
+  (Contributed by Adam Turner and Semyon Moroz in :gh:`130167`.)
 
 
 gc
@@ -2316,42 +2292,90 @@ gc
 * The new :ref:`incremental garbage collector <whatsnew314-incremental-gc>`
   means that maximum pause times are reduced
   by an order of magnitude or more for larger heaps.
+
+  Because of this optimization, the meaning of the results of
+  :meth:`~gc.get_threshold` and :meth:`~gc.set_threshold` have changed,
+  along with :meth:`~gc.get_count` and :meth:`~gc.get_stats`.
+
+  - For backwards compatibility, :meth:`~gc.get_threshold` continues to return
+    a three-item tuple.
+    The first value is the threshold for young collections, as before;
+    the second value determines the rate at which the old collection is scanned
+    (the default is 10, and higher values mean that the old collection
+    is scanned more slowly).
+    The third value is now meaningless and is always zero.
+
+  - :meth:`~gc.set_threshold` now ignores any items after the second.
+
+  - :meth:`~gc.get_count` and :meth:`~gc.get_stats` continue to return
+    the same format of results.
+    The only difference is that instead of the results referring to
+    the young, aging and old generations,
+    the results refer to the young generation
+    and the aging and collecting spaces of the old generation.
+
+  In summary, code that attempted to manipulate the behavior of the cycle GC
+  may not work exactly as intended, but it is very unlikely to be harmful.
+  All other code will work just fine.
+
   (Contributed by Mark Shannon in :gh:`108362`.)
 
 
 io
 ---
-* :mod:`io` which provides the built-in :func:`open` makes less system calls
-  when opening regular files as well as reading whole files. Reading a small
-  operating system cached file in full is up to 15% faster.
-  :func:`pathlib.Path.read_bytes` has the most optimizations for reading a
-  file's bytes in full. (Contributed by Cody Maloney and Victor Stinner in
-  :gh:`120754` and :gh:`90102`.)
+
+* Opening and reading files now executes fewer system calls.
+  Reading a small operating system cached file in full is up to 15% faster.
+  (Contributed by Cody Maloney and Victor Stinner
+  in :gh:`120754` and :gh:`90102`.)
+
+
+pathlib
+-------
+
+* :func:`Path.read_bytes <pathlib.Path.read_bytes>` now uses unbuffered mode
+  to open files, which is between 9% and 17% faster to read in full.
+  (Contributed by Cody Maloney in :gh:`120754`.)
+
+
+pdb
+---
+
+* :mod:`pdb` now supports two backends, based on either
+  :func:`sys.settrace` or :mod:`sys.monitoring`.
+  Using the :ref:`pdb CLI <pdb-cli>` or :func:`breakpoint`
+  will always use the :mod:`sys.monitoring` backend.
+  Explicitly instantiating :class:`pdb.Pdb` and its derived classes
+  will use the :func:`sys.settrace` backend by default, which is configurable.
+  (Contributed by Tian Gao in :gh:`124533`.)
 
 
 uuid
 ----
 
-* Improve generation of :class:`~uuid.UUID` objects via their dedicated
-  functions:
-
-  * :func:`~uuid.uuid3` and :func:`~uuid.uuid5` are both roughly 40% faster
-    for 16-byte names and 20% faster for 1024-byte names. Performance for
-    longer names remains unchanged.
-  * :func:`~uuid.uuid4` is 30% faster.
+* :func:`~uuid.uuid3` and :func:`~uuid.uuid5` are now both roughly 40% faster
+  for 16-byte names and 20% faster for 1024-byte names.
+  Performance for longer names remains unchanged.
+  (Contributed by Bénédikt Tran in :gh:`128150`.)
 
+* :func:`~uuid.uuid4` is now c. 30% faster.
   (Contributed by Bénédikt Tran in :gh:`128150`.)
 
 
 zlib
 ----
 
-* On Windows, ``zlib-ng`` is now used as the implementation of the
-  :mod:`zlib` module. This should produce compatible and comparable
-  results with better performance, though it is worth noting that
-  ``zlib.Z_BEST_SPEED`` (1) may result in significantly less
-  compression than the previous implementation (while also significantly
-  reducing the time taken to compress).
+* On Windows, `zlib-ng <https://github.com/zlib-ng/zlib-ng>`__
+  is now used as the implementation of the :mod:`zlib` module
+  in the default binaries.
+  There are no known incompatabilities between ``zlib-ng``
+  and the previously-used ``zlib`` implementation.
+  This should result in better performance at all compression levels.
+
+  It is worth noting that ``zlib.Z_BEST_SPEED`` (``1``) may result in
+  significantly less compression than the previous implementation,
+  whilst also significantly reducing the time taken to compress.
+
   (Contributed by Steve Dower in :gh:`91349`.)