bpo-34637: Make the *start* argument for *sum()* visible as a keyword argument. (GH-9208)

rhettinger · web-flow · commit 9dfa0fe587ea · 2018-09-12T10:54:06.000-07:00
diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
@@ -1488,6 +1488,9 @@ are always available.  They are listed here in alphabetical order.
    see :func:`math.fsum`\.  To concatenate a series of iterables, consider using
    :func:`itertools.chain`.
 
+   .. versionchanged:: 3.8
+      The *start* parameter can be specified as a keyword argument.
+
 .. function:: super([type[, object-or-type]])
 
    Return a proxy object that delegates method calls to a parent or sibling
diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
@@ -1297,6 +1297,9 @@ def test_sum(self):
         self.assertEqual(sum(iter(Squares(10))), 285)
         self.assertEqual(sum([[1], [2], [3]], []), [1, 2, 3])
 
+        self.assertEqual(sum(range(10), 1000), 1045)
+        self.assertEqual(sum(range(10), start=1000), 1045)
+
         self.assertRaises(TypeError, sum)
         self.assertRaises(TypeError, sum, 42)
         self.assertRaises(TypeError, sum, ['a', 'b', 'c'])
diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-09-11-17-25-44.bpo-34637.HSLqY4.rst b/Misc/NEWS.d/next/Core and Builtins/2018-09-11-17-25-44.bpo-34637.HSLqY4.rst
@@ -0,0 +1 @@
+Make the *start* argument to *sum()* visible as a keyword argument.
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
@@ -2272,8 +2272,8 @@ With an argument, equivalent to object.__dict__.");
 sum as builtin_sum
 
     iterable: object
-    start: object(c_default="NULL") = 0
     /
+    start: object(c_default="NULL") = 0
 
 Return the sum of a 'start' value (default: 0) plus an iterable of numbers
 
@@ -2284,7 +2284,7 @@ reject non-numeric types.
 
 static PyObject *
 builtin_sum_impl(PyObject *module, PyObject *iterable, PyObject *start)
-/*[clinic end generated code: output=df758cec7d1d302f input=3b5b7a9d7611c73a]*/
+/*[clinic end generated code: output=df758cec7d1d302f input=162b50765250d222]*/
 {
     PyObject *result = start;
     PyObject *temp, *item, *iter;
diff --git a/Python/clinic/bltinmodule.c.h b/Python/clinic/bltinmodule.c.h

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+Make the start argument to sum() visible as a keyword argument.`
Original file line number	Diff line number	Diff line change
`@@ -2272,8 +2272,8 @@ With an argument, equivalent to object.__dict__.");`
`2272`	`2272`	`sum as builtin_sum`
`2273`	`2273`
`2274`	`2274`	`iterable: object`
`2275`		`- start: object(c_default="NULL") = 0`
`2276`	`2275`	`/`
	`2276`	`+ start: object(c_default="NULL") = 0`
`2277`	`2277`
`2278`	`2278`	`Return the sum of a 'start' value (default: 0) plus an iterable of numbers`
`2279`	`2279`
`@@ -2284,7 +2284,7 @@ reject non-numeric types.`
`2284`	`2284`
`2285`	`2285`	`static PyObject *`
`2286`	`2286`	`builtin_sum_impl(PyObject module, PyObject iterable, PyObject *start)`
`2287`		`-/[clinic end generated code: output=df758cec7d1d302f input=3b5b7a9d7611c73a]/`
	`2287`	`+/[clinic end generated code: output=df758cec7d1d302f input=162b50765250d222]/`
`2288`	`2288`	`{`
`2289`	`2289`	`PyObject *result = start;`
`2290`	`2290`	`PyObject temp, item, *iter;`