Add __class_getitem__ support to all datetime types

Author: m-aciek

Doc/library/datetime.rst

@@ -950,6 +950,11 @@ Constructor:
    .. versionchanged:: 3.6
       Added the *fold* parameter.
 
+   .. versionchanged:: 3.16
+      :class:`!datetime` now supports the subscript (``[]``) operator for creating
+      :class:`generic aliases <types.GenericAlias>`, e.g., ``datetime[tzinfo]``.
+      See :pep:`585` and :ref:`types-genericalias`.
+
 
 Other constructors, all class methods:
 

Lib/_pydatetime.py

@@ -9,6 +9,7 @@
 import time as _time
 import math as _math
 import sys
+import types as _types
 from operator import index as _index
 
 def _cmp(x, y):
@@ -2432,6 +2433,8 @@ def __reduce_ex__(self, protocol):
     def __reduce__(self):
         return self.__reduce_ex__(2)
 
+    __class_getitem__ = classmethod(_types.GenericAlias)
+
 
 datetime.min = datetime(1, 1, 1)
 datetime.max = datetime(9999, 12, 31, 23, 59, 59, 999999)

Lib/test/datetimetester.py

@@ -130,6 +130,23 @@ def test_divide_and_round(self):
         self.assertEqual(dar(6, -4), -2)
         self.assertEqual(dar(-6, -4), 2)
 
+    def test_datetime_class_getitem(self):
+        """Test that datetime class supports subscripting via __class_getitem__."""
+        from types import GenericAlias
+        datetime = datetime_module
+        
+        # Test datetime class can be subscripted
+        alias = datetime.datetime[tzinfo]
+        self.assertIsInstance(alias, GenericAlias)
+        self.assertIs(alias.__origin__, datetime.datetime)
+        self.assertEqual(alias.__args__, (tzinfo,))
+        
+        # Test multiple type arguments
+        alias_multi = datetime.datetime[tzinfo, str]
+        self.assertIsInstance(alias_multi, GenericAlias)
+        self.assertIs(alias_multi.__origin__, datetime.datetime)
+        self.assertEqual(alias_multi.__args__, (tzinfo, str))
+
 
 #############################################################################
 # tzinfo tests

Modules/_datetimemodule.c

@@ -7305,6 +7305,9 @@ static PyMethodDef datetime_methods[] = {
     DATETIME_DATETIME___REDUCE_EX___METHODDEF
     DATETIME_DATETIME___REDUCE___METHODDEF
 
+    {"__class_getitem__", Py_GenericAlias, METH_O|METH_CLASS,
+     PyDoc_STR("See PEP 585")},
+
     {NULL,      NULL}
 };