python · hauntsaninja · Sep 17, 2024 · Sep 11, 2024 · Sep 11, 2024 · Sep 11, 2024
@@ -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+$|^-\d*\.\d+$')
+        self._negative_number_matcher = _re.compile(r'^-\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

@@ -5716,6 +5716,31 @@ def test_double_dash(self):
         args = parser.parse_args(['--foo', 'a', 'b', '--', 'c', 'd'])
         self.assertEqual(NS(foo=['a', 'b'], bar=['c', 'd']), args)
 
+    def test_negative_number_success(self):
+        parser = argparse.ArgumentParser()
+        parser.add_argument('--int', type=int)
+        parser.add_argument('--float', type=float)
+
+        args = parser.parse_args(['--int', '-1000', '--float', '-1000.0'])
+        self.assertEqual(NS(int=-1000, float=-1000.0), args)
+
+        args = parser.parse_args(['--int', '-1_000', '--float', '-1_000.0'])
+        self.assertEqual(NS(int=-1000, float=-1000.0), args)
+
+        args = parser.parse_args(['--int', '-1_000_000', '--float', '-1_000_000.0'])
+        self.assertEqual(NS(int=-1000000, float=-1000000.0), args)
+
+    def test_negative_float_failure(self):
+        parser = ErrorRaisingArgumentParser(prog='PROG')
+        parser.add_argument('--float', type=float)
+
+        with self.assertRaises(ArgumentParserError) as cm:
+            parser.parse_args(['--float', '-_.45'])
+            parser.parse_args(['--float', '-1__000.0'])
+            parser.parse_args(['--float', '-1_000.0_0'])
+
+        self.assertRegex(str(cm.exception), r'error: argument --float: expected one argument')
+
 
 # ===========================
 # parse_intermixed_args tests

diff --git a/Misc/NEWS.d/next/Library/2024-09-11-19-05-32.gh-issue-123945.jLwybB.rst b/Misc/NEWS.d/next/Library/2024-09-11-19-05-32.gh-issue-123945.jLwybB.rst
@@ -0,0 +1 @@
+Fix a bug where argparse doesn't recognize negative numbers with underscores
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Fix a bug where argparse doesn't recognize negative numbers with underscores
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