gh-137165: Add non-zero-padded Windows support for datetime.strftime

Author: marat

Lib/test/datetimetester.py

@@ -14,6 +14,7 @@
 import textwrap
 import unittest
 import warnings
+import platform
 
 from array import array
 
@@ -1587,6 +1588,17 @@ def test_strftime(self):
         self.assertEqual(t.strftime("m:%m d:%d y:%y"), "m:03 d:02 y:05")
         self.assertEqual(t.strftime(""), "") # SF bug #761337
         self.assertEqual(t.strftime('x'*1000), 'x'*1000) # SF bug #1556784
+        self.assertEqual(t.strftime("m:%-m d:%-d"), "m:3 d:2") # SF bug #137165
+        if platform.system() == 'Darwin': # SF bug #137165
+            self.assertEqual(t.strftime("m:%-m d:%-d y:%-y"), "m:3 d:2 y:05")
+        elif (
+            platform.system() == 'Linux'
+            and platform.machine() == 'x86_64'
+            and 'android' in platform.platform()
+        ):
+            raise self.skipTest('Android x86_64 is not support non-zero-padded strftime')
+        else:
+            self.assertEqual(t.strftime("m:%-m d:%-d y:%-y"), "m:3 d:2 y:5")
 
         self.assertRaises(TypeError, t.strftime) # needs an arg
         self.assertRaises(TypeError, t.strftime, "one", "two") # too many args
@@ -3889,6 +3901,14 @@ def test_strftime(self):
         self.assertEqual(t.strftime('%H %M %S %f'), "01 02 03 000004")
         # A naive object replaces %z, %:z and %Z with empty strings.
         self.assertEqual(t.strftime("'%z' '%:z' '%Z'"), "'' '' ''")
+        if (
+            platform.system() == 'Linux'
+            and platform.machine() == 'x86_64'
+            and 'android' in platform.platform()
+        ):
+            raise self.skipTest('Android x86_64 is not support non-zero-padded strftime')
+        else:
+            self.assertEqual(t.strftime('%-H %-M %-S %f'), "1 2 3 000004") # SF bug #137165
 
         # bpo-34482: Check that surrogates don't cause a crash.
         try:

Misc/NEWS.d/next/Library/2025-09-16-15-36-18.gh-issue-137165.AclPcn.rst

@@ -0,0 +1,2 @@
+Add support for Windows non-zero-padded formatting directives in
+:func:`datetime.datetime.strftime` (e.g., ``"m:%-m d:%-d y:%-y"``).

Modules/_datetimemodule.c

@@ -2002,6 +2002,21 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
             }
             continue;
         }
+        #ifdef MS_WINDOWS
+        /* non-0-pad Windows support */
+        else if (ch == '-' && i < flen) {
+            Py_UCS4 next_ch = PyUnicode_READ_CHAR(format, i);
+            if (strchr("dHImMSUwWyY", next_ch) != NULL) {
+                i++;
+                replacement = PyUnicode_FromFormat("%s%c", "%#", next_ch);
+                if (replacement == NULL) {
+                    goto Error;
+                }
+            } else {
+                continue;
+            }
+        }
+        #endif
         else {
             /* percent followed by something else */
             continue;
@@ -2034,6 +2049,28 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
     result = PyObject_CallFunctionObjArgs(strftime,
                                           newformat, timetuple, NULL);
     Py_DECREF(newformat);
+    if (result == NULL && PyErr_ExceptionMatches(PyExc_ValueError)) {
+        PyObject *err_type, *err_value, *err_tb;
+        PyErr_Fetch(&err_type, &err_value, &err_tb);
+
+        Py_UCS4 bad_char = 0;
+        if (i > 0 && i <= PyUnicode_GET_LENGTH(format)) {
+            bad_char = PyUnicode_READ_CHAR(format, i-1);
+        }
+
+        PyObject *new_msg = PyUnicode_FromFormat(
+            "%U (invalid at position %zd, char '%C')",
+            err_value ? err_value : PyUnicode_FromString("ValueError"),
+            i > 0 ? i-1 : 0,
+            bad_char
+        );
+
+        Py_XDECREF(err_value);
+        Py_XDECREF(err_tb);
+        PyErr_Restore(err_type, new_msg, NULL);
+
+        goto Done;
+    }
 
  Done:
     Py_XDECREF(freplacement);