GH-123945: Update regex for parsing negative numbers that contain underscores

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+$|^-\d*\.\d+$')
+        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

Lib/test/test_argparse.py

@@ -1493,7 +1493,9 @@ class TestOptionLike(ParserTestCase):
     failures = ['-x', '-y2.5', '-xa', '-x -a',
                 '-x -3', '-x -3.5', '-3 -3.5',
                 '-x -2.5', '-x -2.5 a', '-3 -.5',
-                'a x -1', '-x -1 a', '-3 -1 a']
+                'a x -1', '-x -1 a', '-3 -1 a',
+                '-x -_.45 -3 1_000', '-x -1_000.0_45 -3 1_000',
+                '-x -1__000_000.0 -3 1_000_000',]
     successes = [
         ('', NS(x=None, y=None, z=[])),
         ('-x 2.5', NS(x=2.5, y=None, z=[])),
@@ -1506,6 +1508,11 @@ class TestOptionLike(ParserTestCase):
         ('a -x 1', NS(x=1.0, y=None, z=['a'])),
         ('-x 1 a', NS(x=1.0, y=None, z=['a'])),
         ('-3 1 a', NS(x=None, y=1.0, z=['a'])),
+        ('-x-1_000.0 -3 1_000.0', NS(x=-1000.0, y=1000.0, z=[])),
+        ('-x-1_000 -3 1_000', NS(x=-1000, y=1000, z=[])),
+        ('-x-1_000_000.0 -3 1_000_000.0', NS(x=-1000000.0, y=1000000.0, z=[])),
+        ('-x-1_000_000_000.0 -3 1_000_000_000.0', NS(x=-1000000000.0, y=1000000000.0, z=[])),
+
     ]
 
 

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