GH-124321: Fix argparse negative number parsing to capture -.5(GH-124322)

savannahostrowski · AA-Turner · web-flow · commit dc4831271714 · 2024-09-23T11:16:55.000-07:00
Co-authored-by: Adam Turner &lt;9087854+AA-Turner@users.noreply.github.com&gt;
diff --git a/Lib/argparse.py b/Lib/argparse.py
@@ -1360,7 +1360,7 @@ def __init__(self,
         self._defaults = {}
 
         # determines whether an "option" looks like a negative number
-        self._negative_number_matcher = _re.compile(r'^-\d[\d_]*(\.\d[\d_]*)?$')
+        self._negative_number_matcher = _re.compile(r'^-(?:\d+(?:_\d+)*(?:\.\d+(?:_\d+)*)?|\.\d+(?:_\d+)*)$')
 
         # whether or not there are any optionals that look like negative
         # numbers -- uses a list so it can be shared and edited
diff --git a/Lib/test/test_argparse.py b/Lib/test/test_argparse.py
@@ -2111,6 +2111,8 @@ class TestNegativeNumber(ParserTestCase):
         ('--int -1_000_000 --float -1_000_000.0', NS(int=-1000000, float=-1000000.0)),
         ('--float -1_000.0', NS(int=None, float=-1000.0)),
         ('--float -1_000_000.0_0', NS(int=None, float=-1000000.0)),
+        ('--float -.5', NS(int=None, float=-0.5)),
+        ('--float -.5_000', NS(int=None, float=-0.5)),
     ]
 
 class TestInvalidAction(TestCase):

Original file line number	Diff line number	Diff line change
`@@ -2111,6 +2111,8 @@ class TestNegativeNumber(ParserTestCase):`
`2111`	`2111`	`('--int -1_000_000 --float -1_000_000.0', NS(int=-1000000, float=-1000000.0)),`
`2112`	`2112`	`('--float -1_000.0', NS(int=None, float=-1000.0)),`
`2113`	`2113`	`('--float -1_000_000.0_0', NS(int=None, float=-1000000.0)),`
	`2114`	`+ ('--float -.5', NS(int=None, float=-0.5)),`
	`2115`	`+ ('--float -.5_000', NS(int=None, float=-0.5)),`
`2114`	`2116`	`]`
`2115`	`2117`
`2116`	`2118`	`class TestInvalidAction(TestCase):`