gh-130662: Accept leading zeros in precision/width for Fraction's formatting (#130663)

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

diff --git a/Lib/fractions.py b/Lib/fractions.py
index 063f28478c73386b3a9d529ff3b428ca3e893fc2..cb05ae7c2003f0751dfa7baa1149eb516cef24ce 100644 (file)
--- a/Lib/fractions.py
+++ b/Lib/fractions.py
@@ -168,9 +168,9 @@ _FLOAT_FORMAT_SPECIFICATION_MATCHER = re.compile(r"""
     # A '0' that's *not* followed by another digit is parsed as a minimum width
     # rather than a zeropad flag.
     (?P<zeropad>0(?=[0-9]))?
-    (?P<minimumwidth>0|[1-9][0-9]*)?
+    (?P<minimumwidth>[0-9]+)?
     (?P<thousands_sep>[,_])?
-    (?:\.(?P<precision>0|[1-9][0-9]*))?
+    (?:\.(?P<precision>[0-9]+))?
     (?P<presentation_type>[eEfFgG%])
 """, re.DOTALL | re.VERBOSE).fullmatch
 

diff --git a/Lib/test/test_fractions.py b/Lib/test/test_fractions.py
index 96b3f30519459bdba20ca354d3edf78238a77e7e..d1d2739856c0923e733db6364a39551ab7e8d56f 100644 (file)
--- a/Lib/test/test_fractions.py
+++ b/Lib/test/test_fractions.py
@@ -1518,6 +1518,8 @@ class FractionTest(unittest.TestCase):
             (F(51, 1000), '.1f', '0.1'),
             (F(149, 1000), '.1f', '0.1'),
             (F(151, 1000), '.1f', '0.2'),
+            (F(22, 7), '.02f', '3.14'),  # issue gh-130662
+            (F(22, 7), '005.02f', '03.14'),
         ]
         for fraction, spec, expected in testcases:
             with self.subTest(fraction=fraction, spec=spec):
@@ -1616,12 +1618,6 @@ class FractionTest(unittest.TestCase):
             '=010%',
             '>00.2f',
             '>00f',
-            # Too many zeros - minimum width should not have leading zeros
-            '006f',
-            # Leading zeros in precision
-            '.010f',
-            '.02f',
-            '.000f',
             # Missing precision
             '.e',
             '.f',

diff --git a/Misc/NEWS.d/next/Library/2025-06-02-14-28-30.gh-issue-130662.EIgIR8.rst b/Misc/NEWS.d/next/Library/2025-06-02-14-28-30.gh-issue-130662.EIgIR8.rst
new file mode 100644 (file)
index 0000000..e07200f
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-06-02-14-28-30.gh-issue-130662.EIgIR8.rst
@@ -0,0 +1,3 @@
+Accept leading zeros in precision and width fields for
+:class:`~fractions.Fraction` formatting, for example ``format(Fraction(1,
+3), '.016f')``.