gh-41431: Add datetime.time.strptime() and datetime.date.strptime() (#120752)

* Python implementation

* C implementation

* Test `date.strptime`

* Test `time.strptime`

* 📜🤖 Added by blurb_it.

* Update whatsnew

* Update documentation

* Add leap year note

* Update 2024-06-19-19-53-42.gh-issue-41431.gnkUc5.rst

* Apply suggestions from code review

Co-authored-by: Bénédikt Tran <[email protected]>

* Remove parentheses

* Use helper function

* Remove bad return

* Link to github issue

* Fix directive

* Apply suggestions from code review

Co-authored-by: Paul Ganssle <[email protected]>

* Fix test cases

---------

Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: Bénédikt Tran <[email protected]>
Co-authored-by: Paul Ganssle <[email protected]>

Author: 4 people

Doc/library/datetime.rst

@@ -548,6 +548,39 @@ Other constructors, all class methods:
 
    .. versionadded:: 3.8
 
+.. classmethod:: date.strptime(date_string, format)
+
+   Return a :class:`.date` corresponding to *date_string*, parsed according to
+   *format*. This is equivalent to::
+
+     date(*(time.strptime(date_string, format)[0:3]))
+
+   :exc:`ValueError` is raised if the date_string and format
+   can't be parsed by :func:`time.strptime` or if it returns a value which isn't a
+   time tuple.  See also :ref:`strftime-strptime-behavior` and
+   :meth:`date.fromisoformat`.
+
+   .. note::
+
+      If *format* specifies a day of month without a year a
+      :exc:`DeprecationWarning` is emitted.  This is to avoid a quadrennial
+      leap year bug in code seeking to parse only a month and day as the
+      default year used in absence of one in the format is not a leap year.
+      Such *format* values may raise an error as of Python 3.15.  The
+      workaround is to always include a year in your *format*.  If parsing
+      *date_string* values that do not have a year, explicitly add a year that
+      is a leap year before parsing:
+
+      .. doctest::
+
+         >>> from datetime import date
+         >>> date_string = "02/29"
+         >>> when = date.strptime(f"{date_string};1984", "%m/%d;%Y")  # Avoids leap year bug.
+         >>> when.strftime("%B %d")  # doctest: +SKIP
+         'February 29'
+
+   .. versionadded:: 3.14
+
 
 Class attributes:
 
@@ -1827,7 +1860,7 @@ In Boolean contexts, a :class:`.time` object is always considered to be true.
    details.
 
 
-Other constructor:
+Other constructors:
 
 .. classmethod:: time.fromisoformat(time_string)
 
@@ -1869,6 +1902,22 @@ Other constructor:
       Previously, this method only supported formats that could be emitted by
       :meth:`time.isoformat`.
 
+.. classmethod:: time.strptime(date_string, format)
+
+   Return a :class:`.time` corresponding to *date_string*, parsed according to
+   *format*.
+
+   If *format* does not contain microseconds or timezone information, this is equivalent to::
+
+     time(*(time.strptime(date_string, format)[3:6]))
+
+   :exc:`ValueError` is raised if the *date_string* and *format*
+   cannot be parsed by :func:`time.strptime` or if it returns a value which is not a
+   time tuple.  See also :ref:`strftime-strptime-behavior` and
+   :meth:`time.fromisoformat`.
+
+   .. versionadded:: 3.14
+
 
 Instance methods:
 
@@ -2367,24 +2416,22 @@ Class attributes:
 ``strftime(format)`` method, to create a string representing the time under the
 control of an explicit format string.
 
-Conversely, the :meth:`datetime.strptime` class method creates a
-:class:`.datetime` object from a string representing a date and time and a
-corresponding format string.
+Conversely, the :meth:`date.strptime`, :meth:`datetime.strptime` and
+:meth:`time.strptime` class methods create an object from a string
+representing the time and a corresponding format string.
 
 The table below provides a high-level comparison of :meth:`~.datetime.strftime`
 versus :meth:`~.datetime.strptime`:
 
-+----------------+--------------------------------------------------------+------------------------------------------------------------------------------+
-|                | ``strftime``                                           | ``strptime``                                                                 |
-+================+========================================================+==============================================================================+
-| Usage          | Convert object to a string according to a given format | Parse a string into a :class:`.datetime` object given a corresponding format |
-+----------------+--------------------------------------------------------+------------------------------------------------------------------------------+
-| Type of method | Instance method                                        | Class method                                                                 |
-+----------------+--------------------------------------------------------+------------------------------------------------------------------------------+
-| Method of      | :class:`date`; :class:`.datetime`; :class:`.time`      | :class:`.datetime`                                                           |
-+----------------+--------------------------------------------------------+------------------------------------------------------------------------------+
-| Signature      | ``strftime(format)``                                   | ``strptime(date_string, format)``                                            |
-+----------------+--------------------------------------------------------+------------------------------------------------------------------------------+
++----------------+--------------------------------------------------------+------------------------------------------------------------+
+|                | ``strftime``                                           | ``strptime``                                               |
++================+========================================================+============================================================+
+| Usage          | Convert object to a string according to a given format | Parse a string into an object given a corresponding format |
++----------------+--------------------------------------------------------+------------------------------------------------------------+
+| Type of method | Instance method                                        | Class method                                               |
++----------------+--------------------------------------------------------+------------------------------------------------------------+
+| Signature      | ``strftime(format)``                                   | ``strptime(date_string, format)``                          |
++----------------+--------------------------------------------------------+------------------------------------------------------------+
 
 
    .. _format-codes:

Doc/whatsnew/3.14.rst

@@ -285,6 +285,12 @@ operator
   (Contributed by Raymond Hettinger and Nico Mexis in :gh:`115808`.)
 
 
+datetime
+--------
+
+Add :meth:`datetime.time.strptime` and :meth:`datetime.date.strptime`.
+(Contributed by Wannes Boeykens in :gh:`41431`.)
+
 os
 --
 

Include/internal/pycore_global_objects_fini_generated.h

@@ -257,7 +257,9 @@ struct _Py_global_strings {
         STRUCT_FOR_ID(_shutdown)
         STRUCT_FOR_ID(_slotnames)
         STRUCT_FOR_ID(_strptime)
-        STRUCT_FOR_ID(_strptime_datetime)
+        STRUCT_FOR_ID(_strptime_datetime_date)
+        STRUCT_FOR_ID(_strptime_datetime_datetime)
+        STRUCT_FOR_ID(_strptime_datetime_time)
         STRUCT_FOR_ID(_type_)
         STRUCT_FOR_ID(_uninitialized_submodules)
         STRUCT_FOR_ID(_warn_unawaited_coroutine)

Include/internal/pycore_global_strings.h

@@ -951,6 +951,7 @@ class date:
     fromtimestamp()
     today()
     fromordinal()
+    strptime()
 
     Operators:
 
@@ -1051,6 +1052,12 @@ def fromisocalendar(cls, year, week, day):
         This is the inverse of the date.isocalendar() function"""
         return cls(*_isoweek_to_gregorian(year, week, day))
 
+    @classmethod
+    def strptime(cls, date_string, format):
+        """Parse a date string according to the given format (like time.strptime())."""
+        import _strptime
+        return _strptime._strptime_datetime_date(cls, date_string, format)
+
     # Conversions to string
 
     def __repr__(self):
@@ -1371,6 +1378,7 @@ class time:
     Constructors:
 
     __new__()
+    strptime()
 
     Operators:
 
@@ -1429,6 +1437,12 @@ def __new__(cls, hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold
         self._fold = fold
         return self
 
+    @classmethod
+    def strptime(cls, date_string, format):
+        """string, format -> new time parsed from a string (like time.strptime())."""
+        import _strptime
+        return _strptime._strptime_datetime_time(cls, date_string, format)
+
     # Read-only field accessors
     @property
     def hour(self):
@@ -2152,7 +2166,7 @@ def __str__(self):
     def strptime(cls, date_string, format):
         'string, format -> new datetime parsed from a string (like time.strptime()).'
         import _strptime
-        return _strptime._strptime_datetime(cls, date_string, format)
+        return _strptime._strptime_datetime_datetime(cls, date_string, format)
 
     def utcoffset(self):
         """Return the timezone offset as timedelta positive east of UTC (negative west of

Include/internal/pycore_runtime_init_generated.h

@@ -567,18 +567,40 @@ def _strptime_time(data_string, format="%a %b %d %H:%M:%S %Y"):
     tt = _strptime(data_string, format)[0]
     return time.struct_time(tt[:time._STRUCT_TM_ITEMS])
 
-def _strptime_datetime(cls, data_string, format="%a %b %d %H:%M:%S %Y"):
-    """Return a class cls instance based on the input string and the
+def _strptime_datetime_date(cls, data_string, format="%a %b %d %Y"):
+    """Return a date instance based on the input string and the
+    format string."""
+    tt, _, _ = _strptime(data_string, format)
+    args = tt[:3]
+    return cls(*args)
+
+def _parse_tz(tzname, gmtoff, gmtoff_fraction):
+    tzdelta = datetime_timedelta(seconds=gmtoff, microseconds=gmtoff_fraction)
+    if tzname:
+        return datetime_timezone(tzdelta, tzname)
+    else:
+        return datetime_timezone(tzdelta)
+
+def _strptime_datetime_time(cls, data_string, format="%H:%M:%S"):
+    """Return a time instance based on the input string and the
     format string."""
     tt, fraction, gmtoff_fraction = _strptime(data_string, format)
     tzname, gmtoff = tt[-2:]
-    args = tt[:6] + (fraction,)
-    if gmtoff is not None:
-        tzdelta = datetime_timedelta(seconds=gmtoff, microseconds=gmtoff_fraction)
-        if tzname:
-            tz = datetime_timezone(tzdelta, tzname)
-        else:
-            tz = datetime_timezone(tzdelta)
-        args += (tz,)
+    args = tt[3:6] + (fraction,)
+    if gmtoff is None:
+        return cls(*args)
+    else:
+        tz = _parse_tz(tzname, gmtoff, gmtoff_fraction)
+        return cls(*args, tz)
 
-    return cls(*args)
+def _strptime_datetime_datetime(cls, data_string, format="%a %b %d %H:%M:%S %Y"):
+    """Return a datetime instance based on the input string and the
+    format string."""
+    tt, fraction, gmtoff_fraction = _strptime(data_string, format)
+    tzname, gmtoff = tt[-2:]
+    args = tt[:6] + (fraction,)
+    if gmtoff is None:
+        return cls(*args)
+    else:
+        tz = _parse_tz(tzname, gmtoff, gmtoff_fraction)
+        return cls(*args, tz)