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gh-87790: support thousands separators for formatting fractional part of Fraction's #132204

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gh-87790: support thousands separators for formatting fractional part of Fraction's #132204

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gh-87790: support thousands separators for formatting fractional part…
skirpichev Apr 7, 2025
074a349
Merge branch 'main' into frac-sep-Fraction/87790
skirpichev Jun 24, 2025
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10 changes: 9 additions & 1 deletion Lib/fractions.py
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Original file line number Diff line number Diff line change
Expand Up @@ -170,7 +170,11 @@ def _round_to_figures(n, d, figures):
(?P<zeropad>0(?=[0-9]))?
(?P<minimumwidth>[0-9]+)?
(?P<thousands_sep>[,_])?
(?:\.(?P<precision>[0-9]+))?
(?:\.
(?=[,_0-9]) # lookahead for digit or separator
(?P<precision>[0-9]+)?
(?P<frac_separators>[,_])?
)?
(?P<presentation_type>[eEfFgG%])
""", re.DOTALL | re.VERBOSE).fullmatch

Expand Down Expand Up @@ -499,6 +503,7 @@ def _format_float_style(self, match):
minimumwidth = int(match["minimumwidth"] or "0")
thousands_sep = match["thousands_sep"]
precision = int(match["precision"] or "6")
frac_sep = match["frac_separators"] or ""
presentation_type = match["presentation_type"]
trim_zeros = presentation_type in "gG" and not alternate_form
trim_point = not alternate_form
Expand Down Expand Up @@ -552,6 +557,9 @@ def _format_float_style(self, match):
if trim_zeros:
frac_part = frac_part.rstrip("0")
separator = "" if trim_point and not frac_part else "."
if frac_sep:
frac_part = frac_sep.join(frac_part[pos:pos + 3]
for pos in range(0, len(frac_part), 3))
trailing = separator + frac_part + suffix

# Do zero padding if required.
Expand Down
13 changes: 13 additions & 0 deletions Lib/test/test_fractions.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1322,6 +1322,8 @@ def test_format_e_presentation_type(self):
# Thousands separators
(F('1234567.123456'), ',.5e', '1.23457e+06'),
(F('123.123456'), '012_.2e', '0_001.23e+02'),
# Thousands separators for fractional part (or for integral too)
(F('1234567.123456'), '.5_e', '1.234_57e+06'),
# z flag is legal, but never makes a difference to the output
(F(-1, 7**100), 'z.6e', '-3.091690e-85'),
]
Expand Down Expand Up @@ -1447,6 +1449,12 @@ def test_format_f_presentation_type(self):
(F('1234567'), ',.2f', '1,234,567.00'),
(F('12345678'), ',.2f', '12,345,678.00'),
(F('12345678'), ',f', '12,345,678.000000'),
# Thousands separators for fractional part (or for integral too)
(F('123456.789123123'), '._f', '123456.789_123'),
(F('123456.789123123'), '.7_f', '123456.789_123_1'),
(F('123456.789123123'), '.9_f', '123456.789_123_123'),
(F('123456.789123123'), '.,f', '123456.789,123'),
(F('123456.789123123'), '_.,f', '123_456.789,123'),
# Underscore as thousands separator
(F(2, 3), '_.2f', '0.67'),
(F(2, 3), '_.7f', '0.6666667'),
Expand Down Expand Up @@ -1623,6 +1631,11 @@ def test_invalid_formats(self):
'.f',
'.g',
'.%',
# Thousands separators before precision
'._6e',
'._6f',
'._6g',
'._6%',
# Z instead of z for negative zero suppression
'Z.2f'
# z flag not supported for general formatting
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2025-04-07-10-20-16.gh-issue-87790.X2SjJe.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Support underscore and comma as thousands separators in the fractional part
for :class:`~fractions.Fraction`'s formatting. Patch by Sergey B Kirpichev.
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