gh-140764: Make "missed comma" syntax warning less cryptic

Lib/test/test_grammar.py

@@ -1520,7 +1520,7 @@ def test_warn_missed_comma(self):
         def check(test):
             self.check_syntax_warning(test, msg)
 
-        msg=r'is not callable; perhaps you missed a comma\?'
+        msg=r'is not callable; did you miss a comma to separate sequence elements\?'
         check('[(1, 2) (3, 4)]')
         check('[(x, y) (3, 4)]')
         check('[[1, 2] (3, 4)]')
@@ -1543,7 +1543,7 @@ def check(test):
         check('[t"{x}" (3, 4)]')
         check('[t"x={x}" (3, 4)]')
 
-        msg=r'is not subscriptable; perhaps you missed a comma\?'
+        msg=r'is not subscriptable; did you miss a comma to separate sequence elements\?'
         check('[{1, 2} [i, j]]')
         check('[{i for i in range(5)} [i, j]]')
         check('[(i for i in range(5)) [i, j]]')
@@ -1557,7 +1557,7 @@ def check(test):
         check('[t"{x}" [i, j]]')
         check('[t"x={x}" [i, j]]')
 
-        msg=r'indices must be integers or slices, not tuple; perhaps you missed a comma\?'
+        msg=r'indices must be integers or slices, not tuple; did you miss a comma to separate sequence elements\?'
         check('[(1, 2) [i, j]]')
         check('[(x, y) [i, j]]')
         check('[[1, 2] [i, j]]')

Misc/NEWS.d/next/Core_and_Builtins/2025-12-07-10-37-32.gh-issue-140764.kABu5f.rst

@@ -0,0 +1 @@
+Improve syntax warning messages for missing commas in sequences. The messages now say "did you miss a comma to separate sequence elements?" instead of "perhaps you missed a comma?".

Python/codegen.c

@@ -3650,7 +3650,7 @@ check_caller(compiler *c, expr_ty e)
     case Interpolation_kind: {
         location loc = LOC(e);
         return _PyCompile_Warn(c, loc, "'%.200s' object is not callable; "
-                                       "perhaps you missed a comma?",
+                                       "did you miss a comma to separate sequence elements?",
                                        infer_type(e)->tp_name);
     }
     default:
@@ -3681,7 +3681,7 @@ check_subscripter(compiler *c, expr_ty e)
     case Lambda_kind: {
         location loc = LOC(e);
         return _PyCompile_Warn(c, loc, "'%.200s' object is not subscriptable; "
-                                       "perhaps you missed a comma?",
+                                       "did you miss a comma to separate sequence elements?",
                                        infer_type(e)->tp_name);
     }
     default:
@@ -3716,7 +3716,7 @@ check_index(compiler *c, expr_ty e, expr_ty s)
         location loc = LOC(e);
         return _PyCompile_Warn(c, loc, "%.200s indices must be integers "
                                        "or slices, not %.200s; "
-                                       "perhaps you missed a comma?",
+                                       "did you miss a comma to separate sequence elements?",
                                        infer_type(e)->tp_name,
                                        index_type->tp_name);
     }