From 19a5631bd9a4145237aea030a18892057dfc59f6 Mon Sep 17 00:00:00 2001
From: Sergey B Kirpichev <skirpichev@gmail.com>
Date: Mon, 2 Jun 2025 16:30:52 +0300
Subject: [PATCH] gh-130662: Accept leading zeros in precision/width for
 Decimal's formatting (GH-132549) (cherry picked from commit
 9c72658e49806eae52346a0905c1c176d3d49a2f)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Sergey B Kirpichev <skirpichev@gmail.com>
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
---
 Lib/_pydecimal.py                                             | 4 ++--
 Lib/test/test_decimal.py                                      | 2 ++
 .../Library/2025-06-02-14-36-28.gh-issue-130662.Gpr2GB.rst    | 3 +++
 3 files changed, 7 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2025-06-02-14-36-28.gh-issue-130662.Gpr2GB.rst

diff --git a/Lib/_pydecimal.py b/Lib/_pydecimal.py
index 46fa9ffcb1e056..781b38ec26ba33 100644
--- a/Lib/_pydecimal.py
+++ b/Lib/_pydecimal.py
@@ -6120,9 +6120,9 @@ def _convert_for_comparison(self, other, equality_op=False):
 (?P<no_neg_0>z)?
 (?P<alt>\#)?
 (?P<zeropad>0)?
-(?P<minimumwidth>(?!0)\d+)?
+(?P<minimumwidth>\d+)?
 (?P<thousands_sep>[,_])?
-(?:\.(?P<precision>0|(?!0)\d+))?
+(?:\.(?P<precision>\d+))?
 (?P<type>[eEfFgGn%])?
 \z
 """, re.VERBOSE|re.DOTALL)
diff --git a/Lib/test/test_decimal.py b/Lib/test/test_decimal.py
index 9e298401dc3dcc..ca2b0b18fb0a6d 100644
--- a/Lib/test/test_decimal.py
+++ b/Lib/test/test_decimal.py
@@ -982,6 +982,7 @@ def test_formatting(self):
             ('.0f', '0e-2', '0'),
             ('.0f', '3.14159265', '3'),
             ('.1f', '3.14159265', '3.1'),
+            ('.01f', '3.14159265', '3.1'), # leading zero in precision
             ('.4f', '3.14159265', '3.1416'),
             ('.6f', '3.14159265', '3.141593'),
             ('.7f', '3.14159265', '3.1415926'), # round-half-even!
@@ -1067,6 +1068,7 @@ def test_formatting(self):
             ('8,', '123456', ' 123,456'),
             ('08,', '123456', '0,123,456'), # special case: extra 0 needed
             ('+08,', '123456', '+123,456'), # but not if there's a sign
+            ('008,', '123456', '0,123,456'), # leading zero in width
             (' 08,', '123456', ' 123,456'),
             ('08,', '-123456', '-123,456'),
             ('+09,', '123456', '+0,123,456'),
diff --git a/Misc/NEWS.d/next/Library/2025-06-02-14-36-28.gh-issue-130662.Gpr2GB.rst b/Misc/NEWS.d/next/Library/2025-06-02-14-36-28.gh-issue-130662.Gpr2GB.rst
new file mode 100644
index 00000000000000..d97d937376a9d0
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-06-02-14-36-28.gh-issue-130662.Gpr2GB.rst
@@ -0,0 +1,3 @@
++Accept leading zeros in precision and width fields for
++:class:`~decimal.Decimal` formatting, for example ``format(Decimal(1.25),
+'.016f')``.