gh-100929: Add %F format code to strptime

Doc/library/datetime.rst

@@ -1155,6 +1155,9 @@ Other constructors, all class methods:
          >>> when.strftime("%B %d")  # doctest: +SKIP
          'February 29'
 
+   .. versionchanged::
+      Added the ``%F`` directive.
+
 
 Class attributes:
 
@@ -2593,6 +2596,9 @@ convenience. These parameters all correspond to ISO 8601 date values.
 |           | (empty string if the object is | +06:34:15,             |       |
 |           | naive).                        | -03:07:12.345216       |       |
 +-----------+--------------------------------+------------------------+-------+
+| ``%F``    | Optional microseconds as a     | (empty), .000003,      | \(11) |
+|           | decimal number.                | .123456, .3            |       |
++-----------+--------------------------------+------------------------+-------+
 
 These may not be available on all platforms when used with the :meth:`~.datetime.strftime`
 method. The ISO 8601 year and ISO 8601 week directives are not interchangeable
@@ -2765,6 +2771,10 @@ Notes:
       :exc:`DeprecationWarning`. In 3.15 or later we may change this into
       an error or change the default year to a leap year. See :gh:`70647`.
 
+(11)
+  The ``%F`` directive can only be used with :meth:`~.datetime.strptime`
+  and :meth:`~.time.strptime`.
+
 .. rubric:: Footnotes
 
 .. [#] If, that is, we ignore the effects of Relativity

Doc/library/time.rst

@@ -614,12 +614,27 @@ Functions
    except for recognizing UTC and GMT which are always known (and are considered to
    be non-daylight savings timezones).
 
+   The ``%F`` directive is exclusive to :func:`!time.strptime` and allows for
+   optional microseconds as a decimal.::
+
+      >>> import time
+      >>> time.strptime("09:10:13", "%H:%M:%S%F")
+      time.struct_time(tm_year=1900, tm_mon=1, tm_mday=1, tm_hour=9, tm_min=10,
+                       tm_sec=13, tm_wday=0, tm_yday=1, tm_isdst=-1)
+      >>> time.strptime("09:10:13.22", "%H:%M:%S%F")
+      time.struct_time(tm_year=1900, tm_mon=1, tm_mday=1, tm_hour=9, tm_min=10,
+                       tm_sec=13, tm_wday=0, tm_yday=1, tm_isdst=-1)
+
+
    Only the directives specified in the documentation are supported.  Because
    ``strftime()`` is implemented per platform it can sometimes offer more
    directives than those listed.  But ``strptime()`` is independent of any platform
    and thus does not necessarily support all directives available that are not
    documented as supported.
 
+   .. versionchanged::
+      Added the ``%F`` directive.
+
 
 .. class:: struct_time
 

Lib/_strptime.py

@@ -288,6 +288,7 @@ def __init__(self, locale_time=None):
             # The " [1-9]" part of the regex is to make %c from ANSI C work
             'd': r"(?P<d>3[0-1]|[1-2]\d|0[1-9]|[1-9]| [1-9])",
             'f': r"(?P<f>[0-9]{1,6})",
+            'F': r"(?:\.(?P<F>[0-9]{1,6}))?",
             'H': r"(?P<H>2[0-3]|[0-1]\d|\d)",
             'I': r"(?P<I>1[0-2]|0[1-9]|[1-9]| [1-9])",
             'G': r"(?P<G>\d\d\d\d)",
@@ -522,6 +523,10 @@ def _strptime(data_string, format="%a %b %d %H:%M:%S %Y"):
             # Pad to always return microseconds.
             s += "0" * (6 - len(s))
             fraction = int(s)
+        elif group_key == "F":
+            s = found_dict["F"] or "0"
+            s += "0" * (6 - len(s))
+            fraction = int(s)
         elif group_key == 'A':
             weekday = locale_time.f_weekday.index(found_dict['A'].lower())
         elif group_key == 'a':

Lib/test/datetimetester.py

@@ -2890,6 +2890,16 @@ def test_strptime(self):
             strptime("-00:02:01.000003", "%z").utcoffset(),
             -timedelta(minutes=2, seconds=1, microseconds=3)
         )
+
+        # Test %F
+        inputs = [
+            (self.theclass(2025, 3, 23, 13, 2, 47, 197000), "2025-03-23 13:02:47.197", "%Y-%m-%d %H:%M:%S%F"),
+            (self.theclass(2025, 3, 23, 13, 2, 47), "2025-03-23 13:02:47", "%Y-%m-%d %H:%M:%S%F"),
+        ]
+        for expected, string, format in inputs:
+            with self.subTest(expected=expected, string=string, format=format):
+                self.assertEqual(expected, self.theclass.strptime(string, format))
+
         # Only local timezone and UTC are supported
         for tzseconds, tzname in ((0, 'UTC'), (0, 'GMT'),
                                  (-_time.timezone, _time.tzname[0])):
@@ -3858,6 +3868,15 @@ def test_strftime(self):
         # A naive object replaces %z, %:z and %Z with empty strings.
         self.assertEqual(t.strftime("'%z' '%:z' '%Z'"), "'' '' ''")
 
+        # Test %F
+        inputs = [
+            (self.theclass(13, 2, 47, 197000), "13:02:47.197", "%H:%M:%S%F"),
+            (self.theclass(13, 2, 47), "13:02:47", "%H:%M:%S%F"),
+        ]
+        for expected, string, format in inputs:
+            with self.subTest(expected=expected, string=string, format=format):
+                self.assertEqual(expected, self.theclass.strptime(string, format))
+
         # bpo-34482: Check that surrogates don't cause a crash.
         try:
             t.strftime('%H\ud800%M')

Lib/test/test_strptime.py

@@ -364,6 +364,16 @@ def test_fraction(self):
         tup, frac, _ = _strptime._strptime(str(d), format="%Y-%m-%d %H:%M:%S.%f")
         self.assertEqual(frac, d.microsecond)
 
+    def test_optional_fraction(self):
+        # Test optional microseconds
+        import datetime
+        d = datetime.datetime(2012, 12, 20, 12, 34, 56, 78987)
+        tup, frac, _ = _strptime._strptime(str(d), format="%Y-%m-%d %H:%M:%S%F")
+        self.assertEqual(frac, d.microsecond)
+        dn = datetime.datetime(2012, 12, 20, 12, 34, 56)
+        tup, frac, _ = _strptime._strptime(str(dn), format="%Y-%m-%d %H:%M:%S%F")
+        self.assertEqual(frac, dn.microsecond)
+
     def test_weekday(self):
         # Test weekday directives
         self.roundtrip('%w', 6)

Misc/NEWS.d/next/Library/2025-03-23-16-17-00.gh-issue-100929.awbdyu.rst

@@ -0,0 +1,2 @@
+Add ``%F`` format code to :func:`time.strptime` and :func:`datetime.datetime.strptime`
+which allows for optional microseconds.