bpo-38237: Let pow() support keyword arguments (GH-16302) (GH-16320)

Backported with release manager approval

2 files changed, 32 insertions, 26 deletions

diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index c8d34c9..0d3f7ed 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -1797,22 +1797,22 @@ builtin_ord(PyObject *module, PyObject *c)
 /*[clinic input]
 pow as builtin_pow
 
-    x: object
-    y: object
-    z: object = None
-    /
+    base: object
+    exp: object
+    mod: object = None
 
-Equivalent to x**y (with two arguments) or x**y % z (with three arguments)
+Equivalent to base**exp (with two arguments) or base**exp % mod (with three arguments)
 
 Some types, such as ints, are able to use a more efficient algorithm when
 invoked using the three argument form.
 [clinic start generated code]*/
 
 static PyObject *
-builtin_pow_impl(PyObject *module, PyObject *x, PyObject *y, PyObject *z)
-/*[clinic end generated code: output=50a14d5d130d404b input=653d57d38d41fc07]*/
+builtin_pow_impl(PyObject *module, PyObject *base, PyObject *exp,
+                 PyObject *mod)
+/*[clinic end generated code: output=3ca1538221bbf15f input=bd72d0a0ec8e5eb5]*/
 {
-    return PyNumber_Power(x, y, z);
+    return PyNumber_Power(base, exp, mod);
 }
 
 
diff --git a/Python/clinic/bltinmodule.c.h b/Python/clinic/bltinmodule.c.h
index b936b0c..f6c5b7c 100644
--- a/Python/clinic/bltinmodule.c.h
+++ b/Python/clinic/bltinmodule.c.h
@@ -608,39 +608,45 @@ PyDoc_STRVAR(builtin_ord__doc__,
     {"ord", (PyCFunction)builtin_ord, METH_O, builtin_ord__doc__},
 
 PyDoc_STRVAR(builtin_pow__doc__,
-"pow($module, x, y, z=None, /)\n"
+"pow($module, /, base, exp, mod=None)\n"
 "--\n"
 "\n"
-"Equivalent to x**y (with two arguments) or x**y % z (with three arguments)\n"
+"Equivalent to base**exp (with two arguments) or base**exp % mod (with three arguments)\n"
 "\n"
 "Some types, such as ints, are able to use a more efficient algorithm when\n"
 "invoked using the three argument form.");
 
 #define BUILTIN_POW_METHODDEF    \
-    {"pow", (PyCFunction)(void(*)(void))builtin_pow, METH_FASTCALL, builtin_pow__doc__},
+    {"pow", (PyCFunction)(void(*)(void))builtin_pow, METH_FASTCALL|METH_KEYWORDS, builtin_pow__doc__},
 
 static PyObject *
-builtin_pow_impl(PyObject *module, PyObject *x, PyObject *y, PyObject *z);
+builtin_pow_impl(PyObject *module, PyObject *base, PyObject *exp,
+                 PyObject *mod);
 
 static PyObject *
-builtin_pow(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
+builtin_pow(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
 {
     PyObject *return_value = NULL;
-    PyObject *x;
-    PyObject *y;
-    PyObject *z = Py_None;
-
-    if (!_PyArg_CheckPositional("pow", nargs, 2, 3)) {
+    static const char * const _keywords[] = {"base", "exp", "mod", NULL};
+    static _PyArg_Parser _parser = {NULL, _keywords, "pow", 0};
+    PyObject *argsbuf[3];
+    Py_ssize_t noptargs = nargs + (kwnames ? PyTuple_GET_SIZE(kwnames) : 0) - 2;
+    PyObject *base;
+    PyObject *exp;
+    PyObject *mod = Py_None;
+
+    args = _PyArg_UnpackKeywords(args, nargs, NULL, kwnames, &_parser, 2, 3, 0, argsbuf);
+    if (!args) {
         goto exit;
     }
-    x = args[0];
-    y = args[1];
-    if (nargs < 3) {
-        goto skip_optional;
+    base = args[0];
+    exp = args[1];
+    if (!noptargs) {
+        goto skip_optional_pos;
     }
-    z = args[2];
-skip_optional:
-    return_value = builtin_pow_impl(module, x, y, z);
+    mod = args[2];
+skip_optional_pos:
+    return_value = builtin_pow_impl(module, base, exp, mod);
 
 exit:
     return return_value;
@@ -849,4 +855,4 @@ builtin_issubclass(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=4e118c2cd2cd98f3 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=1e2a6185e05ecd11 input=a9049054013a1b77]*/