Re-introduce datetime.py

Author: pganssle

Lib/_pydatetime.py

@@ -2624,26 +2624,3 @@ def _name_from_offset(delta):
 # small dst() may get within its bounds; and it doesn't even matter if some
 # perverse time zone returns a negative dst()).  So a breaking case must be
 # pretty bizarre, and a tzinfo subclass can override fromutc() if it is.
-
-try:
-    from _datetime import *
-except ImportError:
-    pass
-else:
-    # Clean up unused names
-    del (_DAYNAMES, _DAYS_BEFORE_MONTH, _DAYS_IN_MONTH, _DI100Y, _DI400Y,
-         _DI4Y, _EPOCH, _MAXORDINAL, _MONTHNAMES, _build_struct_time,
-         _check_date_fields, _check_time_fields,
-         _check_tzinfo_arg, _check_tzname, _check_utc_offset, _cmp, _cmperror,
-         _date_class, _days_before_month, _days_before_year, _days_in_month,
-         _format_time, _format_offset, _index, _is_leap, _isoweek1monday, _math,
-         _ord2ymd, _time, _time_class, _tzinfo_class, _wrap_strftime, _ymd2ord,
-         _divide_and_round, _parse_isoformat_date, _parse_isoformat_time,
-         _parse_hh_mm_ss_ff, _IsoCalendarDate, _isoweek_to_gregorian,
-         _find_isoformat_datetime_separator, _FRACTION_CORRECTION,
-         _is_ascii_digit)
-    # XXX Since import * above excludes names that start with _,
-    # docstring does not get overwritten. In the future, it may be
-    # appropriate to maintain a single module level docstring and
-    # remove the following line.
-    from _datetime import __doc__

Lib/datetime.py

@@ -0,0 +1,9 @@
+try:
+    from _datetime import *
+    from _datetime import __doc__
+except ImportError:
+    from _pydatetime import *
+    from _pydatetime import __doc__
+
+__all__ = ("date", "datetime", "time", "timedelta", "timezone", "tzinfo",
+           "MINYEAR", "MAXYEAR")

Misc/NEWS.d/next/Library/2023-04-19-16-08-53.gh-issue-84976.HwbzlD.rst

@@ -0,0 +1,5 @@
+Create a new ``Lib/_pydatetime.py`` file that defines the Python version of
+the ``datetime`` module, and make ``datetime`` import the contents of the
+new library only if the C implementation is missing. Currently, the full
+Python implementation is defined and then deleted if the C implementation is
+not available, slowing down ``import datetime`` unnecessarily.