https://github.com/python/cpython/commit/90a5b4402bc6b8f44a9fe9a5299721b1887b50f8
commit: 90a5b4402bc6b8f44a9fe9a5299721b1887b50f8
branch: main
author: Sergey B Kirpichev <skirpic...@gmail.com>
committer: hugovk <1324225+hug...@users.noreply.github.com>
date: 2025-07-07T11:16:27+03:00
summary:
gh-87790: support thousands separators for formatting fractional part of
Decimal (#132202)
Co-authored-by: Serhiy Storchaka <storch...@gmail.com>
files:
A Misc/NEWS.d/next/Library/2025-04-07-09-53-54.gh-issue-87790.6nj3zQ.rst
M Lib/_pydecimal.py
M Lib/test/test_decimal.py
diff --git a/Lib/_pydecimal.py b/Lib/_pydecimal.py
index 781b38ec26ba33..9b8e42a2342536 100644
--- a/Lib/_pydecimal.py
+++ b/Lib/_pydecimal.py
@@ -6122,7 +6122,11 @@ def _convert_for_comparison(self, other,
equality_op=False):
(?P<zeropad>0)?
(?P<minimumwidth>\d+)?
(?P<thousands_sep>[,_])?
-(?:\.(?P<precision>\d+))?
+(?:\.
+ (?=[\d,_]) # lookahead for digit or separator
+ (?P<precision>\d+)?
+ (?P<frac_separators>[,_])?
+)?
(?P<type>[eEfFgGn%])?
\z
""", re.VERBOSE|re.DOTALL)
@@ -6215,6 +6219,9 @@ def _parse_format_specifier(format_spec,
_localeconv=None):
format_dict['grouping'] = [3, 0]
format_dict['decimal_point'] = '.'
+ if format_dict['frac_separators'] is None:
+ format_dict['frac_separators'] = ''
+
return format_dict
def _format_align(sign, body, spec):
@@ -6334,6 +6341,11 @@ def _format_number(is_negative, intpart, fracpart, exp,
spec):
sign = _format_sign(is_negative, spec)
+ frac_sep = spec['frac_separators']
+ if fracpart and frac_sep:
+ fracpart = frac_sep.join(fracpart[pos:pos + 3]
+ for pos in range(0, len(fracpart), 3))
+
if fracpart or spec['alt']:
fracpart = spec['decimal_point'] + fracpart
diff --git a/Lib/test/test_decimal.py b/Lib/test/test_decimal.py
index ef64b878805d77..08a8f4c3b36bd6 100644
--- a/Lib/test/test_decimal.py
+++ b/Lib/test/test_decimal.py
@@ -1089,6 +1089,15 @@ def test_formatting(self):
('07_', '1234.56', '1_234.56'),
('_', '1.23456789', '1.23456789'),
('_%', '123.456789', '12_345.6789%'),
+ # and now for something completely different...
+ ('.,', '1.23456789', '1.234,567,89'),
+ ('._', '1.23456789', '1.234_567_89'),
+ ('.6_f', '12345.23456789', '12345.234_568'),
+ (',._%', '123.456789', '12,345.678_9%'),
+ (',._e', '123456', '1.234_56e+5'),
+ (',.4_e', '123456', '1.234_6e+5'),
+ (',.3_e', '123456', '1.235e+5'),
+ (',._E', '123456', '1.234_56E+5'),
# negative zero: default behavior
('.1f', '-0', '-0.0'),
@@ -1162,6 +1171,10 @@ def test_formatting(self):
# bytes format argument
self.assertRaises(TypeError, Decimal(1).__format__, b'-020')
+ # precision or fractional part separator should follow after dot
+ self.assertRaises(ValueError, format, Decimal(1), '.f')
+ self.assertRaises(ValueError, format, Decimal(1), '._6f')
+
def test_negative_zero_format_directed_rounding(self):
with self.decimal.localcontext() as ctx:
ctx.rounding = ROUND_CEILING
diff --git
a/Misc/NEWS.d/next/Library/2025-04-07-09-53-54.gh-issue-87790.6nj3zQ.rst
b/Misc/NEWS.d/next/Library/2025-04-07-09-53-54.gh-issue-87790.6nj3zQ.rst
new file mode 100644
index 00000000000000..cf80c71271bbd1
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-04-07-09-53-54.gh-issue-87790.6nj3zQ.rst
@@ -0,0 +1,2 @@
+Support underscore and comma as thousands separators in the fractional part
+for :class:`~decimal.Decimal`'s formatting. Patch by Sergey B Kirpichev.
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