bpo-34903: Document that some strptime formats only require 1 digit (GH-14149)

For datetime.datetime.strptime(), the leading zero for some two-digit formats is optional.

This adds a footnote to the strftime/strptime documentation to reflect this fact, and adds some tests to ensure that it is true.

bpo-34903
(cherry picked from commit 6b9c204ee77a0de87d6f51a3d4547a18604cef9e)

Co-authored-by: Mike Gleen <mike.gleen@gmail.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index b9bf49476f..2f8975d8c0 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -2387,6 +2387,7 @@ class TestDateTime(TestDate):
                 self.assertEqual(expected, got)
 
         strptime = self.theclass.strptime
+
         self.assertEqual(strptime("+0002", "%z").utcoffset(), 2 * MINUTE)
         self.assertEqual(strptime("-0002", "%z").utcoffset(), -2 * MINUTE)
         self.assertEqual(
@@ -2421,6 +2422,40 @@ class TestDateTime(TestDate):
         with self.assertRaises(ValueError): strptime("-2400", "%z")
         with self.assertRaises(ValueError): strptime("-000", "%z")
 
+    def test_strptime_single_digit(self):
+        # bpo-34903: Check that single digit dates and times are allowed.
+
+        strptime = self.theclass.strptime
+
+        with self.assertRaises(ValueError):
+            # %y does require two digits.
+            newdate = strptime('01/02/3 04:05:06', '%d/%m/%y %H:%M:%S')
+        dt1 = self.theclass(2003, 2, 1, 4, 5, 6)
+        dt2 = self.theclass(2003, 1, 2, 4, 5, 6)
+        dt3 = self.theclass(2003, 2, 1, 0, 0, 0)
+        dt4 = self.theclass(2003, 1, 25, 0, 0, 0)
+        inputs = [
+            ('%d', '1/02/03 4:5:6', '%d/%m/%y %H:%M:%S', dt1),
+            ('%m', '01/2/03 4:5:6', '%d/%m/%y %H:%M:%S', dt1),
+            ('%H', '01/02/03 4:05:06', '%d/%m/%y %H:%M:%S', dt1),
+            ('%M', '01/02/03 04:5:06', '%d/%m/%y %H:%M:%S', dt1),
+            ('%S', '01/02/03 04:05:6', '%d/%m/%y %H:%M:%S', dt1),
+            ('%j', '2/03 04am:05:06', '%j/%y %I%p:%M:%S',dt2),
+            ('%I', '02/03 4am:05:06', '%j/%y %I%p:%M:%S',dt2),
+            ('%w', '6/04/03', '%w/%U/%y', dt3),
+            # %u requires a single digit.
+            ('%W', '6/4/2003', '%u/%W/%Y', dt3),
+            ('%V', '6/4/2003', '%u/%V/%G', dt4),
+        ]
+        for reason, string, format, target in inputs:
+            reason = 'test single digit ' + reason
+            with self.subTest(reason=reason,
+                              string=string,
+                              format=format,
+                              target=target):
+                newdate = strptime(string, format)
+                self.assertEqual(newdate, target, msg=reason)
+
     def test_more_timetuple(self):
         # This tests fields beyond those tested by the TestDate.test_timetuple.
         t = self.theclass(2004, 12, 31, 6, 22, 33)