WIP: bpo-1100942: Add datetime.time.strptime and datetime.date.strptime

Doc/library/datetime.rst

@@ -443,6 +443,15 @@ Other constructors, all class methods:
    date.max.toordinal()``. For any date *d*, ``date.fromordinal(d.toordinal()) ==
    d``.
 
+.. classmethod:: date.strptime(date_string, format)
+
+   Return a :class:`date` corresponding to *date_string*, parsed according to
+   *format*. :exc:`ValueError` is raised if the date string and format can't be
+   parsed by :meth:`datetime.time.strptime`, or if time components are present
+   in the format string. For a complete list of formatting directives, see
+   :ref:`strftime-strptime-behavior`.
+
+   .. versionadded:: 3.8
 
 .. classmethod:: date.fromisoformat(date_string)
 
@@ -1426,6 +1435,19 @@ day, and subject to adjustment via a :class:`tzinfo` object.
    If an argument outside those ranges is given, :exc:`ValueError` is raised.  All
    default to ``0`` except *tzinfo*, which defaults to :const:`None`.
 
+
+Other constructors, all class methods:
+
+.. classmethod:: time.strptime(date_string, format)
+
+   Return a :class:`datetime.time` corresponding to *date_string*, parsed
+   according to *format*. :exc:`ValueError` is raised if the date string and
+   format can't be parsed by :meth:`time.strptime`. For a complete list of
+   formatting directives, see :ref:`strftime-strptime-behavior`.
+
+   .. versionadded:: 3.8
+
+
 Class attributes:
 
 
@@ -2021,15 +2043,17 @@ Conversely, the :meth:`datetime.strptime` class method creates a
 corresponding format string. ``datetime.strptime(date_string, format)`` is
 equivalent to ``datetime(*(time.strptime(date_string, format)[0:6]))``, except
 when the format includes sub-second components or timezone offset information,
-which are supported in ``datetime.strptime`` but are discarded by ``time.strptime``.
+which are supported in ``datetime.strptime`` but are discarded by
+:meth:`time.strptime`.
 
-For :class:`.time` objects, the format codes for year, month, and day should not
-be used, as time objects have no such values.  If they're used anyway, ``1900``
-is substituted for the year, and ``1`` for the month and day.
+The :meth:`date.strptime` class method creates a :class:`date` object from a
+string representing a date and a corresponding format string. :exc:`ValueError`
+is raised if the format codes for hours, minutes, seconds, or microseconds are
+used.
 
-For :class:`date` objects, the format codes for hours, minutes, seconds, and
-microseconds should not be used, as :class:`date` objects have no such
-values.  If they're used anyway, ``0`` is substituted for them.
+The :meth:`.time.strptime` class method creates a :class:`.time` object from a
+string representing a time and a corresponding format string. :exc:`ValueError`
+raised if the format codes for year, month, and day are used.
 
 The full set of format codes supported varies across platforms, because Python
 calls the platform C library's :func:`strftime` function, and platform

Doc/whatsnew/3.8.rst

@@ -175,6 +175,15 @@ Added :func:`~gettext.pgettext` and its variants.
 (Contributed by Franz Glasner, Éric Araujo, and Cheryl Sabella in :issue:`2504`.)
 
 
+datetime
+--------
+
+Added :func:`~datetime.date.strptime` and :func:`~datetime.time.strptime`.
+(Patch by Alexander Belopolsky, Amaury Forgeot d'Arc, Berker Peksag, Josh-sf,
+Juraez Bochi, Maciej Szulik, Matheus Vieira Portela. Contributed by Stéphane
+Wirtel)
+
+
 gc
 --
 

Lib/_strptime.py

@@ -17,6 +17,7 @@
 from re import IGNORECASE
 from re import escape as re_escape
 from datetime import (date as datetime_date,
+                      datetime as datetime_datetime,
                       timedelta as datetime_timedelta,
                       timezone as datetime_timezone)
 from _thread import allocate_lock as _thread_allocate_lock
@@ -307,9 +308,9 @@ def _calc_julian_from_V(iso_year, iso_week, iso_weekday):
 
 
 def _strptime(data_string, format="%a %b %d %H:%M:%S %Y"):
-    """Return a 2-tuple consisting of a time struct and an int containing
+    """Return a 3-tuple consisting of a time struct and an int containing
     the number of microseconds based on the input string and the
-    format string."""
+    format string, and the UTC offset."""
 
     for index, arg in enumerate([data_string, format]):
         if not isinstance(arg, str):
@@ -556,6 +557,10 @@ def _strptime(data_string, format="%a %b %d %H:%M:%S %Y"):
             hour, minute, second,
             weekday, julian, tz, tzname, gmtoff), fraction, gmtoff_fraction
 
+date_specs = ('%a', '%A', '%b', '%B', '%c', '%d', '%j', '%m', '%U', '%G',
+              '%u', '%V', '%w', '%W', '%x', '%y', '%Y', '%G', '%u', '%V',)
+time_specs = ('%H', '%I', '%M', '%S', '%f',)
+
 def _strptime_time(data_string, format="%a %b %d %H:%M:%S %Y"):
     """Return a time struct based on the input string and the
     format string."""
@@ -577,3 +582,19 @@ def _strptime_datetime(cls, data_string, format="%a %b %d %H:%M:%S %Y"):
         args += (tz,)
 
     return cls(*args)
+
+def _strptime_datetime_date(data_string, format):
+    """Return a date based on the input string and the format string."""
+    msg = "'{!s}' {} not valid in date format specification."
+    from _datetime import _check_invalid_datetime_specs
+    if _check_invalid_datetime_specs(format, time_specs, msg):
+        _date = _strptime_datetime(datetime_datetime, data_string, format)
+        return _date.date()
+
+def _strptime_datetime_time(data_string, format):
+    """Return a time based on the input string and the format string."""
+    msg = "'{!s}' {} not valid in time format specification."
+    from _datetime import _check_invalid_datetime_specs
+    if _check_invalid_datetime_specs(format, date_specs, msg):
+        _time = _strptime_datetime(datetime_datetime, data_string, format)
+        return _time.time()

Lib/datetime.py

@@ -795,6 +795,7 @@ class date:
     fromtimestamp()
     today()
     fromordinal()
+    strptime()
 
     Operators:
 
@@ -885,6 +886,16 @@ def fromisoformat(cls, date_string):
             raise ValueError(f'Invalid isoformat string: {date_string!r}')
 
 
+    @classmethod
+    def strptime(cls, date_string, format):
+        """string, format -> new date instance parsed from a string.
+
+        >>> datetime.date.strptime('2012/07/20', '%Y/%m/%d')
+        datetime.date(2012, 7, 20)
+        """
+        import _strptime
+        return _strptime._strptime_datetime_date(date_string, format)
+
     # Conversions to string
 
     def __repr__(self):
@@ -1180,6 +1191,7 @@ class time:
     Constructors:
 
     __new__()
+    strptime()
 
     Operators:
 
@@ -1238,6 +1250,16 @@ def __new__(cls, hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold
         self._fold = fold
         return self
 
+    @staticmethod
+    def strptime(time_string, format):
+        """string, format -> new time instance parsed from a string.
+
+        >>> datetime.time.strptime('10:40am', '%H:%M%p')
+        datetime.time(10, 40)
+        """
+        import _strptime
+        return _strptime._strptime_datetime_time(time_string, format)
+
     # Read-only field accessors
     @property
     def hour(self):
@@ -1906,7 +1928,11 @@ def __str__(self):
 
     @classmethod
     def strptime(cls, date_string, format):
-        'string, format -> new datetime parsed from a string (like time.strptime()).'
+        """string, format -> new datetime parsed from a string.
+
+        >>> datetime.datetime.strptime('2012/07/20 10:40am', '%Y/%m/%d %H:%M%p')
+        datetime.datetime(2012, 7, 20, 10, 40)
+        """
         import _strptime
         return _strptime._strptime_datetime(cls, date_string, format)
 

Lib/test/datetimetester.py

@@ -1017,6 +1017,30 @@ def test_delta_non_days_ignored(self):
         dt2 = dt - delta
         self.assertEqual(dt2, dt - days)
 
+    def test_strptime_valid_format(self):
+        tests = [
+            ('2004-12-01', '%Y-%m-%d', date(2004, 12, 1)),
+            ('2004', '%Y', date(2004, 1, 1)),
+        ]
+        for date_string, date_format, expected in tests:
+            with self.subTest(date_string=date_string,
+                              date_format=date_format,
+                              expected=expected):
+                self.assertEqual(expected, date.strptime(date_string, date_format))
+
+    def test_strptime_invalid_format(self):
+        tests = [
+            ('2004-12-01 13:02:47.197', '%Y-%m-%d %H:%M:%S.%f'),
+            ('2018-01-01', ''),
+            ('01', '%M'),
+            ('02', '%H'),
+        ]
+        for hour, format in tests:
+            with self.subTest(hour=hour, format=format):
+                with self.assertRaises(ValueError):
+                    date.strptime(hour, format)
+
+
 class SubclassDate(date):
     sub_var = 1
 
@@ -3105,6 +3129,25 @@ def test_strftime(self):
         except UnicodeEncodeError:
             pass
 
+    def test_strptime_invalid(self):
+        tests = [
+            ('2004-12-01 13:02:47.197', '%Y-%m-%d %H:%M:%S.%f'),
+            ('2004-12-01', '%Y-%m-%d'),
+            ('12:30:15', ''),
+        ]
+        for date_string, date_format in tests:
+            with self.subTest(date_string=date_string, date_format=date_format):
+                with self.assertRaises(ValueError):
+                    time.strptime(date_string, date_format)
+
+    def test_strptime_valid(self):
+        string = '13:02:47.197'
+        format = '%H:%M:%S.%f'
+        result, frac, gmtoff = _strptime._strptime(string, format)
+        expected = self.theclass(*(result[3:6] + (frac, )))
+        got = time.strptime(string, format)
+        self.assertEqual(expected, got)
+
     def test_format(self):
         t = self.theclass(1, 2, 3, 4)
         self.assertEqual(t.__format__(''), str(t))

Misc/NEWS.d/next/Core and Builtins/2018-02-07-10-55-58.bpo-1100942.md4agI.rst

@@ -0,0 +1 @@
+Add :func:`datetime.date.strptime` and :func:`datetime.time.strptime` class methods.