Index: Python/graminit.c
===================================================================
--- Python/graminit.c	(revision 83046)
+++ Python/graminit.c	(working copy)
@@ -189,11 +189,13 @@
     {30, 7},
     {0, 6},
 };
-static arc arcs_8_7[2] = {
+static arc arcs_8_7[3] = {
     {28, 12},
     {32, 3},
+    {0, 7},
 };
-static arc arcs_8_8[1] = {
+static arc arcs_8_8[2] = {
+    {30, 13},
     {0, 8},
 };
 static arc arcs_8_9[2] = {
@@ -206,35 +208,39 @@
     {0, 10},
 };
 static arc arcs_8_11[3] = {
-    {28, 13},
-    {30, 14},
+    {28, 14},
+    {30, 15},
     {0, 11},
 };
 static arc arcs_8_12[3] = {
     {30, 7},
-    {29, 15},
+    {29, 16},
     {0, 12},
 };
-static arc arcs_8_13[2] = {
-    {30, 14},
+static arc arcs_8_13[1] = {
     {0, 13},
 };
 static arc arcs_8_14[2] = {
-    {28, 16},
+    {30, 15},
+    {0, 14},
+};
+static arc arcs_8_15[3] = {
+    {28, 17},
     {32, 3},
+    {0, 15},
 };
-static arc arcs_8_15[1] = {
+static arc arcs_8_16[1] = {
     {24, 6},
 };
-static arc arcs_8_16[3] = {
-    {30, 14},
-    {29, 17},
-    {0, 16},
+static arc arcs_8_17[3] = {
+    {30, 15},
+    {29, 18},
+    {0, 17},
 };
-static arc arcs_8_17[1] = {
-    {24, 13},
+static arc arcs_8_18[1] = {
+    {24, 14},
 };
-static state states_8[18] = {
+static state states_8[19] = {
     {3, arcs_8_0},
     {3, arcs_8_1},
     {3, arcs_8_2},
@@ -242,17 +248,18 @@
     {1, arcs_8_4},
     {4, arcs_8_5},
     {2, arcs_8_6},
-    {2, arcs_8_7},
-    {1, arcs_8_8},
+    {3, arcs_8_7},
+    {2, arcs_8_8},
     {2, arcs_8_9},
     {3, arcs_8_10},
     {3, arcs_8_11},
     {3, arcs_8_12},
-    {2, arcs_8_13},
+    {1, arcs_8_13},
     {2, arcs_8_14},
-    {1, arcs_8_15},
-    {3, arcs_8_16},
-    {1, arcs_8_17},
+    {3, arcs_8_15},
+    {1, arcs_8_16},
+    {3, arcs_8_17},
+    {1, arcs_8_18},
 };
 static arc arcs_9_0[1] = {
     {21, 1},
@@ -304,11 +311,13 @@
     {30, 7},
     {0, 6},
 };
-static arc arcs_10_7[2] = {
+static arc arcs_10_7[3] = {
     {34, 12},
     {32, 3},
+    {0, 7},
 };
-static arc arcs_10_8[1] = {
+static arc arcs_10_8[2] = {
+    {30, 13},
     {0, 8},
 };
 static arc arcs_10_9[2] = {
@@ -321,35 +330,39 @@
     {0, 10},
 };
 static arc arcs_10_11[3] = {
-    {34, 13},
-    {30, 14},
+    {34, 14},
+    {30, 15},
     {0, 11},
 };
 static arc arcs_10_12[3] = {
     {30, 7},
-    {29, 15},
+    {29, 16},
     {0, 12},
 };
-static arc arcs_10_13[2] = {
-    {30, 14},
+static arc arcs_10_13[1] = {
     {0, 13},
 };
 static arc arcs_10_14[2] = {
-    {34, 16},
+    {30, 15},
+    {0, 14},
+};
+static arc arcs_10_15[3] = {
+    {34, 17},
     {32, 3},
+    {0, 15},
 };
-static arc arcs_10_15[1] = {
+static arc arcs_10_16[1] = {
     {24, 6},
 };
-static arc arcs_10_16[3] = {
-    {30, 14},
-    {29, 17},
-    {0, 16},
+static arc arcs_10_17[3] = {
+    {30, 15},
+    {29, 18},
+    {0, 17},
 };
-static arc arcs_10_17[1] = {
-    {24, 13},
+static arc arcs_10_18[1] = {
+    {24, 14},
 };
-static state states_10[18] = {
+static state states_10[19] = {
     {3, arcs_10_0},
     {3, arcs_10_1},
     {3, arcs_10_2},
@@ -357,17 +370,18 @@
     {1, arcs_10_4},
     {4, arcs_10_5},
     {2, arcs_10_6},
-    {2, arcs_10_7},
-    {1, arcs_10_8},
+    {3, arcs_10_7},
+    {2, arcs_10_8},
     {2, arcs_10_9},
     {3, arcs_10_10},
     {3, arcs_10_11},
     {3, arcs_10_12},
-    {2, arcs_10_13},
+    {1, arcs_10_13},
     {2, arcs_10_14},
-    {1, arcs_10_15},
-    {3, arcs_10_16},
-    {1, arcs_10_17},
+    {3, arcs_10_15},
+    {1, arcs_10_16},
+    {3, arcs_10_17},
+    {1, arcs_10_18},
 };
 static arc arcs_11_0[1] = {
     {21, 1},
@@ -1819,11 +1833,11 @@
      "\000\000\020\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
     {263, "parameters", 0, 4, states_7,
      "\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {264, "typedargslist", 0, 18, states_8,
+    {264, "typedargslist", 0, 19, states_8,
      "\000\000\040\200\001\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
     {265, "tfpdef", 0, 4, states_9,
      "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {266, "varargslist", 0, 18, states_10,
+    {266, "varargslist", 0, 19, states_10,
      "\000\000\040\200\001\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
     {267, "vfpdef", 0, 2, states_11,
      "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
Index: Python/ast.c
===================================================================
--- Python/ast.c	(revision 83046)
+++ Python/ast.c	(working copy)
@@ -738,16 +738,20 @@
        and varargslist (lambda definition).
 
        parameters: '(' [typedargslist] ')'
-       typedargslist: ((tfpdef ['=' test] ',')*
-           ('*' [tfpdef] (',' tfpdef ['=' test])* [',' '**' tfpdef]
-           | '**' tfpdef)
-           | tfpdef ['=' test] (',' tfpdef ['=' test])* [','])
+       typedargslist: (tfpdef ['=' test] (',' tfpdef ['=' test])* [',' [
+               '*' [tfpdef] (',' tfpdef ['=' test])* [',' ['**' tfpdef [',']]]
+             | '**' tfpdef [',']]]
+         | '*' [tfpdef] (',' tfpdef ['=' test])* [',' ['**' tfpdef [',']]]
+         | '**' tfpdef [','])
        tfpdef: NAME [':' test]
-       varargslist: ((vfpdef ['=' test] ',')*
-           ('*' [vfpdef] (',' vfpdef ['=' test])*  [',' '**' vfpdef]
-           | '**' vfpdef)
-           | vfpdef ['=' test] (',' vfpdef ['=' test])* [','])
+       varargslist: (vfpdef ['=' test] (',' vfpdef ['=' test])* [',' [
+               '*' [vfpdef] (',' vfpdef ['=' test])* [',' ['**' vfpdef [',']]]
+             | '**' vfpdef [',']]]
+         | '*' [vfpdef] (',' vfpdef ['=' test])* [',' ['**' vfpdef [',']]]
+         | '**' vfpdef [',']
+       )
        vfpdef: NAME
+
     */
     int i, j, k, nposargs = 0, nkwonlyargs = 0;
     int nposdefaults = 0, found_default = 0;
@@ -851,7 +855,8 @@
                 i += 2; /* the name and the comma */
                 break;
             case STAR:
-                if (i+1 >= NCH(n)) {
+                if (i+1 >= NCH(n) ||
+                    (i+2 == NCH(n) && TYPE(CHILD(n, i+1)) == COMMA)) {
                     ast_error(CHILD(n, i),
                         "named arguments must follow bare *");
                     goto error;
Index: Grammar/Grammar
===================================================================
--- Grammar/Grammar	(revision 83046)
+++ Grammar/Grammar	(working copy)
@@ -24,13 +24,18 @@
 decorated: decorators (classdef | funcdef)
 funcdef: 'def' NAME parameters ['->' test] ':' suite
 parameters: '(' [typedargslist] ')'
-typedargslist: (tfpdef ['=' test] (',' tfpdef ['=' test])* [','
-       ['*' [tfpdef] (',' tfpdef ['=' test])* [',' '**' tfpdef] | '**' tfpdef]]
-     |  '*' [tfpdef] (',' tfpdef ['=' test])* [',' '**' tfpdef] | '**' tfpdef)
+typedargslist: (tfpdef ['=' test] (',' tfpdef ['=' test])* [',' [
+        '*' [tfpdef] (',' tfpdef ['=' test])* [',' ['**' tfpdef [',']]]
+      | '**' tfpdef [',']]]
+  | '*' [tfpdef] (',' tfpdef ['=' test])* [',' ['**' tfpdef [',']]]
+  | '**' tfpdef [','])
 tfpdef: NAME [':' test]
-varargslist: (vfpdef ['=' test] (',' vfpdef ['=' test])* [','
-       ['*' [vfpdef] (',' vfpdef ['=' test])* [',' '**' vfpdef] | '**' vfpdef]]
-     |  '*' [vfpdef] (',' vfpdef ['=' test])* [',' '**' vfpdef] | '**' vfpdef)
+varargslist: (vfpdef ['=' test] (',' vfpdef ['=' test])* [',' [
+        '*' [vfpdef] (',' vfpdef ['=' test])* [',' ['**' vfpdef [',']]]
+      | '**' vfpdef [',']]]
+  | '*' [vfpdef] (',' vfpdef ['=' test])* [',' ['**' vfpdef [',']]]
+  | '**' vfpdef [',']
+)
 vfpdef: NAME
 
 stmt: simple_stmt | compound_stmt
Index: Misc/NEWS
===================================================================
--- Misc/NEWS	(revision 83046)
+++ Misc/NEWS	(working copy)
@@ -12,6 +12,9 @@
 Core and Builtins
 -----------------
 
+- Issue #9232: Modify Python's grammar to allow trailing commas in the
+  argument list of a function declaration.  (Example:  f(*, a=3,).)
+
 - Issue #7616: Fix copying of overlapping memoryview slices with the Intel
   compiler.
 
Index: Doc/reference/compound_stmts.rst
===================================================================
--- Doc/reference/compound_stmts.rst	(revision 83046)
+++ Doc/reference/compound_stmts.rst	(working copy)
@@ -429,11 +429,10 @@
    decorators: `decorator`+
    decorator: "@" `dotted_name` ["(" [`argument_list` [","]] ")"] NEWLINE
    dotted_name: `identifier` ("." `identifier`)*
-   parameter_list: (`defparameter` ",")*
-                 : (  "*" [`parameter`] ("," `defparameter`)*
-                 : [, "**" `parameter`]
-                 : | "**" `parameter`
-                 : | `defparameter` [","] )
+   parameter_list: `defparameter` ("," `defparameter`)* ["," [`parameter_list_starargs`]]
+                 : | `parameter_list_starargs`
+   parameter_list_starargs: "*" [`parameter`] ("," `defparameter`)* ["," ["**" `parameter` [","]]]
+                         : | "**" `parameter` [","]
    parameter: `identifier` [":" `expression`]
    defparameter: `parameter` ["=" `expression`]
    funcname: `identifier`
Index: Lib/test/test_grammar.py
===================================================================
--- Lib/test/test_grammar.py	(revision 83046)
+++ Lib/test/test_grammar.py	(working copy)
@@ -278,6 +278,10 @@
         pos2key2dict(1,2,k2=100,tokwarg1=100,tokwarg2=200)
         pos2key2dict(1,2,tokwarg1=100,tokwarg2=200, k2=100)
 
+        self.assertRaises(SyntaxError, eval, "def f(*): pass")
+        self.assertRaises(SyntaxError, eval, "def f(*,): pass")
+        self.assertRaises(SyntaxError, eval, "def f(*, **kwds): pass")
+
         # keyword arguments after *arglist
         def f(*args, **kwargs):
             return args, kwargs
@@ -324,6 +328,23 @@
         check_syntax_error(self, "f(*g(1=2))")
         check_syntax_error(self, "f(**g(1=2))")
 
+        # Check trailing commas are permitted in funcdef argument list
+        def f(a,): pass
+        def f(*args,): pass
+        def f(**kwds,): pass
+        def f(a, *args,): pass
+        def f(a, **kwds,): pass
+        def f(*args, b,): pass
+        def f(*, b,): pass
+        def f(*args, **kwds,): pass
+        def f(a, *args, b,): pass
+        def f(a, *, b,): pass
+        def f(a, *args, **kwds,): pass
+        def f(*args, b, **kwds,): pass
+        def f(*, b, **kwds,): pass
+        def f(a, *args, b, **kwds,): pass
+        def f(a, *, b, **kwds,): pass
+
     def testLambdef(self):
         ### lambdef: 'lambda' [varargslist] ':' test
         l1 = lambda : 0
@@ -342,7 +363,24 @@
         self.assertEqual(l6(1,2), 1+2+20)
         self.assertEqual(l6(1,2,k=10), 1+2+10)
 
+        # check that trailing commas are permitted
+        l10 = lambda a,: 0
+        l11 = lambda *args,: 0
+        l12 = lambda **kwds,: 0
+        l13 = lambda a, *args,: 0
+        l14 = lambda a, **kwds,: 0
+        l15 = lambda *args, b,: 0
+        l16 = lambda *, b,: 0
+        l17 = lambda *args, **kwds,: 0
+        l18 = lambda a, *args, b,: 0
+        l19 = lambda a, *, b,: 0
+        l20 = lambda a, *args, **kwds,: 0
+        l21 = lambda *args, b, **kwds,: 0
+        l22 = lambda *, b, **kwds,: 0
+        l23 = lambda a, *args, b, **kwds,: 0
+        l24 = lambda a, *, b, **kwds,: 0
 
+
     ### stmt: simple_stmt | compound_stmt
     # Tested below