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 +1588,22 @@ 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
+        
+        # SF bug #137165
+        if platform.system() == 'Darwin':
+            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().lower()
+        ):
+            raise self.skipTest('Android x86_64 is not support non-zero-padded strftime')
+        elif platform.system() == 'Windows':
+            self.assertEqual(t.strftime("m:%#m d:%#d y:%#y"), "m:3 d:2 y:5")
+            self.assertEqual(t.strftime("m:%-m d:%-d y:%-y"), "m:3 d:2 y:5")
+        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
@@ -3890,6 +3907,19 @@ def test_strftime(self):
         # A naive object replaces %z, %:z and %Z with empty strings.
         self.assertEqual(t.strftime("'%z' '%:z' '%Z'"), "'' '' ''")
 
+        # SF bug #137165
+        if (
+            platform.system() == 'Linux'
+            and platform.machine() == 'x86_64'
+            and 'android' in platform.platform().lower()
+        ):
+            raise self.skipTest('Android x86_64 is not support non-zero-padded strftime')
+        elif platform.system() == 'Windows':
+            self.assertEqual(t.strftime('%#H %#M %#S %f'), "1 2 3 000004")
+            self.assertEqual(t.strftime('%-H %-M %-S %f'), "1 2 3 000004")
+        else:
+            self.assertEqual(t.strftime('%-H %-M %-S %f'), "1 2 3 000004")
+
         # bpo-34482: Check that surrogates don't cause a crash.
         try:
             t.strftime('%H\ud800%M')

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;