gh-106487: Allow the 'count' argument of str.replace to be a keyword (#106488)

Doc/library/stdtypes.rst

@@ -2014,11 +2014,14 @@ expression support in the :mod:`re` module).
    .. versionadded:: 3.9
 
 
-.. method:: str.replace(old, new[, count])
+.. method:: str.replace(old, new, count=-1)
 
    Return a copy of the string with all occurrences of substring *old* replaced by
-   *new*.  If the optional argument *count* is given, only the first *count*
+   *new*.  If *count* is given, only the first *count* occurrences are replaced.
-   occurrences are replaced.
+   If *count* is not specified or ``-1``, then all occurrences are replaced.
+
+   .. versionchanged:: 3.13
+      *count* is now supported as a keyword argument.
 
 
 .. method:: str.rfind(sub[, start[, end]])

Doc/whatsnew/3.13.rst

@@ -76,7 +76,8 @@ New Features
 Other Language Changes
 ======================
 
-
+* Allow the *count* argument of :meth:`str.replace` to be a keyword.
+  (Contributed by Hugo van Kemenade in :gh:`106487`.)
 
 New Modules
 ===========

Lib/test/string_tests.py

@@ -154,6 +154,12 @@ class BaseTest:
                     self.assertEqual(rem, 0, '%s != 0 for %s' % (rem, i))
                     self.assertEqual(r1, r2, '%s != %s for %s' % (r1, r2, i))
 
+    def test_count_keyword(self):
+        self.assertEqual('aa'.replace('a', 'b', 0), 'aa'.replace('a', 'b', count=0))
+        self.assertEqual('aa'.replace('a', 'b', 1), 'aa'.replace('a', 'b', count=1))
+        self.assertEqual('aa'.replace('a', 'b', 2), 'aa'.replace('a', 'b', count=2))
+        self.assertEqual('aa'.replace('a', 'b', 3), 'aa'.replace('a', 'b', count=3))
+
     def test_find(self):
         self.checkequal(0, 'abcdefghiabc', 'find', 'abc')
         self.checkequal(9, 'abcdefghiabc', 'find', 'abc', 1)

Misc/NEWS.d/next/Core and Builtins/2023-07-06-22-46-05.gh-issue-106487.u3KfAD.rst

@@ -0,0 +1,2 @@
+Allow the *count* argument of :meth:`str.replace` to be a keyword. Patch by
+Hugo van Kemenade.

Objects/clinic/unicodeobject.c.h

@@ -736,7 +736,7 @@ exit:
 }
 
 PyDoc_STRVAR(unicode_replace__doc__,
-"replace($self, old, new, count=-1, /)\n"
+"replace($self, old, new, /, count=-1)\n"
 "--\n"
 "\n"
 "Return a copy with all occurrences of substring old replaced by new.\n"
@@ -749,21 +749,49 @@ PyDoc_STRVAR(unicode_replace__doc__,
 "replaced.");
 
 #define UNICODE_REPLACE_METHODDEF    \
-    {"replace", _PyCFunction_CAST(unicode_replace), METH_FASTCALL, unicode_replace__doc__},
+    {"replace", _PyCFunction_CAST(unicode_replace), METH_FASTCALL|METH_KEYWORDS, unicode_replace__doc__},
 
 static PyObject *
 unicode_replace_impl(PyObject *self, PyObject *old, PyObject *new,
                      Py_ssize_t count);
 
 static PyObject *
-unicode_replace(PyObject *self, PyObject *const *args, Py_ssize_t nargs)
+unicode_replace(PyObject *self, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
 {
     PyObject *return_value = NULL;
+    #if defined(Py_BUILD_CORE) && !defined(Py_BUILD_CORE_MODULE)
+
+    #define NUM_KEYWORDS 1
+    static struct {
+        PyGC_Head _this_is_not_used;
+        PyObject_VAR_HEAD
+        PyObject *ob_item[NUM_KEYWORDS];
+    } _kwtuple = {
+        .ob_base = PyVarObject_HEAD_INIT(&PyTuple_Type, NUM_KEYWORDS)
+        .ob_item = { &_Py_ID(count), },
+    };
+    #undef NUM_KEYWORDS
+    #define KWTUPLE (&_kwtuple.ob_base.ob_base)
+
+    #else  // !Py_BUILD_CORE
+    #  define KWTUPLE NULL
+    #endif  // !Py_BUILD_CORE
+
+    static const char * const _keywords[] = {"", "", "count", NULL};
+    static _PyArg_Parser _parser = {
+        .keywords = _keywords,
+        .fname = "replace",
+        .kwtuple = KWTUPLE,
+    };
+    #undef KWTUPLE
+    PyObject *argsbuf[3];
+    Py_ssize_t noptargs = nargs + (kwnames ? PyTuple_GET_SIZE(kwnames) : 0) - 2;
     PyObject *old;
     PyObject *new;
     Py_ssize_t count = -1;
 
-    if (!_PyArg_CheckPositional("replace", nargs, 2, 3)) {
+    args = _PyArg_UnpackKeywords(args, nargs, NULL, kwnames, &_parser, 2, 3, 0, argsbuf);
+    if (!args) {
         goto exit;
     }
     if (!PyUnicode_Check(args[0])) {
@@ -776,8 +804,8 @@ unicode_replace(PyObject *self, PyObject *const *args, Py_ssize_t nargs)
         goto exit;
     }
     new = args[1];
-    if (nargs < 3) {
+    if (!noptargs) {
-        goto skip_optional;
+        goto skip_optional_pos;
     }
     {
         Py_ssize_t ival = -1;
@@ -791,7 +819,7 @@ unicode_replace(PyObject *self, PyObject *const *args, Py_ssize_t nargs)
         }
         count = ival;
     }
-skip_optional:
+skip_optional_pos:
     return_value = unicode_replace_impl(self, old, new, count);
 
 exit:
@@ -1476,4 +1504,4 @@ skip_optional_pos:
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=0a71c4aeffdf0bc5 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=ee76a1b49cd4cbb3 input=a9049054013a1b77]*/

Objects/unicodeobject.c

@@ -12025,10 +12025,10 @@ str.replace as unicode_replace
 
     old: unicode
     new: unicode
+    /
     count: Py_ssize_t = -1
         Maximum number of occurrences to replace.
         -1 (the default value) means replace all occurrences.
-    /
 
 Return a copy with all occurrences of substring old replaced by new.
 
@@ -12039,7 +12039,7 @@ replaced.
 static PyObject *
 unicode_replace_impl(PyObject *self, PyObject *old, PyObject *new,
                      Py_ssize_t count)
-/*[clinic end generated code: output=b63f1a8b5eebf448 input=147d12206276ebeb]*/
+/*[clinic end generated code: output=b63f1a8b5eebf448 input=3345c455d60a5499]*/
 {
     return replace(self, old, new, count);
 }