From 35c3168b82f87cb55a7165f6e7ecc50152d05b67 Mon Sep 17 00:00:00 2001
From: Heikki Toivonen <308110+heikkitoivonen@users.noreply.github.com>
Date: Mon, 5 Jan 2026 12:22:01 -0800
Subject: [PATCH 1/2] Optimize deepcopy for 1.04x speedup

Gains according to pyperformance:
```
deepcopy:
Mean +- std dev: 411 us +- 2 us -> 396 us +- 3 us: 1.04x faster
Significant (t=28.94)

deepcopy_reduce:
Mean +- std dev: 4.38 us +- 0.05 us -> 4.23 us +- 0.04 us: 1.04x faster
Significant (t=20.05)
```
---
 Lib/copy.py                                                     | 2 +-
 Misc/ACKS                                                       | 1 +
 .../next/Library/2026-01-05-12-20-42.gh-issue-143445.rgxnbL.rst | 1 +
 3 files changed, 3 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Library/2026-01-05-12-20-42.gh-issue-143445.rgxnbL.rst

diff --git a/Lib/copy.py b/Lib/copy.py
index fff7e93c2a1b89..4c024ab5311d2d 100644
--- a/Lib/copy.py
+++ b/Lib/copy.py
@@ -230,7 +230,7 @@ def _reconstruct(x, memo, func, args,
                  *, deepcopy=deepcopy):
     deep = memo is not None
     if deep and args:
-        args = (deepcopy(arg, memo) for arg in args)
+        args = [deepcopy(arg, memo) for arg in args]
     y = func(*args)
     if deep:
         memo[id(x)] = y
diff --git a/Misc/ACKS b/Misc/ACKS
index 671fcf88c75af9..63ddfb89071c0b 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1931,6 +1931,7 @@ James Tocknell
 Bennett Todd
 R Lindsay Todd
 Eugene Toder
+Heikki Toivonen
 Erik Tollerud
 Stephen Tonkin
 Matias Torchinsky
diff --git a/Misc/NEWS.d/next/Library/2026-01-05-12-20-42.gh-issue-143445.rgxnbL.rst b/Misc/NEWS.d/next/Library/2026-01-05-12-20-42.gh-issue-143445.rgxnbL.rst
new file mode 100644
index 00000000000000..918d1a6dc38ed3
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-01-05-12-20-42.gh-issue-143445.rgxnbL.rst
@@ -0,0 +1 @@
+Optimize deepcopy in :mod:`copy`, pyperformance reports 1.04x speedup.

From ef2d3ea5bba0e984b23bdcec921f6bfdf131545e Mon Sep 17 00:00:00 2001
From: Heikki Toivonen <308110+heikkitoivonen@users.noreply.github.com>
Date: Mon, 5 Jan 2026 15:18:53 -0800
Subject: [PATCH 2/2] Update
 Misc/NEWS.d/next/Library/2026-01-05-12-20-42.gh-issue-143445.rgxnbL.rst
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
---
 .../next/Library/2026-01-05-12-20-42.gh-issue-143445.rgxnbL.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/Library/2026-01-05-12-20-42.gh-issue-143445.rgxnbL.rst b/Misc/NEWS.d/next/Library/2026-01-05-12-20-42.gh-issue-143445.rgxnbL.rst
index 918d1a6dc38ed3..f5dea2e49afe2a 100644
--- a/Misc/NEWS.d/next/Library/2026-01-05-12-20-42.gh-issue-143445.rgxnbL.rst
+++ b/Misc/NEWS.d/next/Library/2026-01-05-12-20-42.gh-issue-143445.rgxnbL.rst
@@ -1 +1 @@
-Optimize deepcopy in :mod:`copy`, pyperformance reports 1.04x speedup.
+Speed up :func:`copy.deepcopy` by 1.04x.