bpo-43923: Add support of generic typing.NamedTuple

python · serhiy-storchaka · Mar 9, 2022 · Mar 9, 2022 · Mar 2, 2024 · Oct 9, 2024
commit 939d5f03c1715d0481dfbfd8b8ddd30a4775643d
@@ -1606,6 +1606,12 @@ These are not used in annotations. They are building blocks for declaring types.
           def __repr__(self) -> str:
               return f'<Employee {self.name}, id={self.id}>'
 
+   ``NamedTuple`` subclasses can be generic::
+
+      class Group(NamedTuple, Generic[T]):
+          key: T
+          group: list[T]
+
    Backward-compatible usage::
 
        Employee = NamedTuple('Employee', [('name', str), ('id', int)])
@@ -1624,6 +1630,9 @@ These are not used in annotations. They are building blocks for declaring types.
       Removed the ``_field_types`` attribute in favor of the more
       standard ``__annotations__`` attribute which has the same information.
 
+   .. versionchanged:: 3.11
+      Added support of multiple inheritance with :class:`Generic`.
+
 .. class:: NewType(name, tp)
 
    A helper class to indicate a distinct type to a typechecker,

diff --git a/Doc/whatsnew/3.11.rst b/Doc/whatsnew/3.11.rst
@@ -641,6 +641,13 @@ time
   (Contributed by Benjamin Szőke, Dong-hee Na, Eryk Sun and Victor Stinner in :issue:`21302` and :issue:`45429`.)
 
 
+typing
+------
+
+* :class:`~typing.NamedTuple` subclasses can be generic.
+  (Contributed by Serhiy Storchaka in :issue:`43923`.)
+
+
 unicodedata
 -----------
 

@@ -5278,6 +5278,37 @@ class A:
         with self.assertRaises(TypeError):
             class X(NamedTuple, A):
                 x: int
+        with self.assertRaises(TypeError):
+            class X(NamedTuple, tuple):
+                x: int
+        with self.assertRaises(TypeError):
+            class X(NamedTuple, NamedTuple):
+                x: int
+        class A(NamedTuple):
+            x: int
+        with self.assertRaises(TypeError):
+            class X(NamedTuple, A):
+                y: str
+
+    def test_generic(self):
+        class X(NamedTuple, Generic[T]):
+            x: T
+        self.assertEqual(X.__bases__, (tuple, Generic))
+        self.assertEqual(X.__orig_bases__, (NamedTuple, Generic[T]))
+        self.assertEqual(X.__mro__, (X, tuple, Generic, object))
+
+        A = X[int]
+        self.assertEqual(A.__bases__, (tuple, Generic))
+        self.assertEqual(A.__orig_bases__, (NamedTuple, Generic[T]))
+        self.assertEqual(A.__mro__, (X, tuple, Generic, object))
+        self.assertIs(A.__origin__, X)
+        self.assertEqual(A.__args__, (int,))
+        self.assertEqual(A.__parameters__, ())
+
+        a = A(3)
+        self.assertIs(type(a), X)
+        self.assertEqual(a.x, 3)
+
 
     def test_namedtuple_keyword_usage(self):
         LocalEmployee = NamedTuple("LocalEmployee", name=str, age=int)

@@ -2763,7 +2763,12 @@ def _make_nmtuple(name, types, module, defaults = ()):
 class NamedTupleMeta(type):
 
     def __new__(cls, typename, bases, ns):
-        assert bases[0] is _NamedTuple
+        assert _NamedTuple in bases
+        for base in bases:
+            if base is not _NamedTuple and base is not Generic:
+                raise TypeError('can only inherit from a NamedTuple type '
+                                'and Generic')
+        bases = tuple(tuple if base is _NamedTuple else base for base in bases)
         types = ns.get('__annotations__', {})
         default_names = []
         for field_name in types:
@@ -2777,6 +2782,7 @@ def __new__(cls, typename, bases, ns):
         nm_tpl = _make_nmtuple(typename, types.items(),
                                defaults=[ns[n] for n in default_names],
                                module=ns['__module__'])
+        nm_tpl.__bases__ = bases
         # update from user namespace without overriding special namedtuple attributes
         for key in ns:
             if key in _prohibited:
@@ -2820,9 +2826,7 @@ class Employee(NamedTuple):
 _NamedTuple = type.__new__(NamedTupleMeta, 'NamedTuple', (), {})
 
 def _namedtuple_mro_entries(bases):
-    if len(bases) > 1:
-        raise TypeError("Multiple inheritance with NamedTuple is not supported")
-    assert bases[0] is NamedTuple
+    assert NamedTuple in bases
     return (_NamedTuple,)
 
 NamedTuple.__mro_entries__ = _namedtuple_mro_entries

diff --git a/Misc/NEWS.d/next/Library/2022-04-28-18-45-58.gh-issue-88089.hu9kRk.rst b/Misc/NEWS.d/next/Library/2022-04-28-18-45-58.gh-issue-88089.hu9kRk.rst
@@ -0,0 +1,2 @@
+Add support of multiple inheritance of :class:`typing.NamedTuple` with
+:class:`typing.Generic`.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Add support of multiple inheritance of :class:`typing.NamedTuple` with
		:class:`typing.Generic`.