https://github.com/python/cpython/commit/75d20b2c67e91dd468e7f5fe4ac465e6d32f8c09
commit: 75d20b2c67e91dd468e7f5fe4ac465e6d32f8c09
branch: main
author: Adam Turner <[email protected]>
committer: AA-Turner <[email protected]>
date: 2025-08-15T11:14:45Z
summary:
GH-123299: Copyedit 3.14 What's New: Optimizations (#137789)
files:
M Doc/library/pdb.rst
M Doc/whatsnew/3.14.rst
diff --git a/Doc/library/pdb.rst b/Doc/library/pdb.rst
index f4b51664545be5..90dc6648045f27 100644
--- a/Doc/library/pdb.rst
+++ b/Doc/library/pdb.rst
@@ -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
diff --git a/Doc/whatsnew/3.14.rst b/Doc/whatsnew/3.14.rst
index 0738f8e8564e7b..f33c20fbf31c0a 100644
--- a/Doc/whatsnew/3.14.rst
+++ b/Doc/whatsnew/3.14.rst
@@ -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`.)
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