python · JelleZijlstra · Apr 17, 2025 · Apr 16, 2025 · Apr 16, 2025 · Apr 16, 2025
@@ -3132,6 +3132,21 @@ def x(self): ...
        with self.assertRaisesRegex(TypeError, only_classes_allowed):
            issubclass(1, BadPG)

+    def test_lazy_evaluation_with_subprotocols(self):
+        @runtime_checkable
+        class Base(Protocol):
+            x: int
+
+        @runtime_checkable
+        class Child(Base, Protocol):
+            y: str
+
+        class Capybara:
+            x = 43
+
+        self.assertIsInstance(Capybara(), Base)
+        self.assertNotIsInstance(Capybara(), Child)
+
    def test_implicit_issubclass_between_two_protocols(self):
        @runtime_checkable
        class CallableMembersProto(Protocol):
@@ -3826,6 +3841,7 @@ def meth(self): pass
            '_is_protocol', '_is_runtime_protocol', '__parameters__',
            '__init__', '__annotations__', '__subclasshook__', '__annotate__',
            '__annotations_cache__', '__annotate_func__',
+            '__protocol_attrs_cache__',
        }
        self.assertLessEqual(vars(NonP).keys(), vars(C).keys() | acceptable_extra_attrs)
        self.assertLessEqual(
@@ -4542,10 +4558,15 @@ class classproperty:
            def __get__(self, instance, type):
                raise CustomError

+        @runtime_checkable
+        class Commentable(Protocol):
+            evil = classproperty()
+
+        class Normal:
+            evil = None
+
        with self.assertRaises(TypeError) as cm:
-            @runtime_checkable
-            class Commentable(Protocol):
-                evil = classproperty()
+            isinstance(Normal(), Commentable)

        exc = cm.exception
        self.assertEqual(

@@ -1777,6 +1777,8 @@ class _TypingEllipsis:
    '__parameters__', '__orig_bases__',  '__orig_class__',
    '_is_protocol', '_is_runtime_protocol', '__protocol_attrs__',
    '__non_callable_proto_members__', '__type_params__',
+    '__protocol_attrs_cache__', '__non_callable_proto_members_cache__',
+    '__final__',
 })

 _SPECIAL_NAMES = frozenset({
@@ -1923,9 +1925,11 @@ class _ProtocolMeta(ABCMeta):
    # This metaclass is somewhat unfortunate,
    # but is necessary for several reasons...
    def __new__(mcls, name, bases, namespace, /, **kwargs):
+        is_protocol = False
        if name == "Protocol" and bases == (Generic,):
            pass
        elif Protocol in bases:
+            is_protocol = True
            for base in bases:
                if not (
                    base in {object, Generic}
@@ -1939,12 +1943,10 @@ def __new__(mcls, name, bases, namespace, /, **kwargs):
                        f"Protocols can only inherit from other protocols, "
                        f"got {base!r}"
                    )
-        return super().__new__(mcls, name, bases, namespace, **kwargs)
-
-    def __init__(cls, *args, **kwargs):
-        super().__init__(*args, **kwargs)
-        if getattr(cls, "_is_protocol", False):
-            cls.__protocol_attrs__ = _get_protocol_attrs(cls)
+        cls = super().__new__(mcls, name, bases, namespace, **kwargs)
+        if is_protocol:
+            cls.__protocol_attrs_cache__ = None
+        return cls

    def __subclasscheck__(cls, other):
        if cls is Protocol:
@@ -1997,14 +1999,42 @@ def __instancecheck__(cls, instance):
                val = getattr_static(instance, attr)
            except AttributeError:
                break
-            # this attribute is set by @runtime_checkable:
            if val is None and attr not in cls.__non_callable_proto_members__:
                break
        else:
            return True

        return False

+    @property
+    def __protocol_attrs__(cls):
+        protocol_attrs = cls.__protocol_attrs_cache__
+        if protocol_attrs is None:
+            protocol_attrs = _get_protocol_attrs(cls)
+            cls.__protocol_attrs_cache__ = protocol_attrs
+        return protocol_attrs
+
+    @property
+    def __non_callable_proto_members__(cls):
+        # PEP 544 prohibits using issubclass()
+        # with protocols that have non-method members.
+        non_callable_members = cls.__non_callable_proto_members_cache__  # set by @runtime_checkable
+        if non_callable_members is None:
+            non_callable_members = set()
+            for attr in cls.__protocol_attrs__:
+                try:
+                    is_callable = callable(getattr(cls, attr, None))
+                except Exception as e:
+                    raise TypeError(
+                        f"Failed to determine whether protocol member {attr!r} "
+                        "is a method member"
+                    ) from e
+                else:
+                    if not is_callable:
+                        non_callable_members.add(attr)
+            cls.__non_callable_proto_members_cache__ = non_callable_members
+        return non_callable_members
+

 @classmethod
 def _proto_hook(cls, other):
@@ -2220,22 +2250,7 @@ def close(self): ...
        raise TypeError('@runtime_checkable can be only applied to protocol classes,'
                        ' got %r' % cls)
    cls._is_runtime_protocol = True
-    # PEP 544 prohibits using issubclass()
-    # with protocols that have non-method members.
-    # See gh-113320 for why we compute this attribute here,
-    # rather than in `_ProtocolMeta.__init__`
-    cls.__non_callable_proto_members__ = set()
-    for attr in cls.__protocol_attrs__:
-        try:
-            is_callable = callable(getattr(cls, attr, None))
-        except Exception as e:
-            raise TypeError(
-                f"Failed to determine whether protocol member {attr!r} "
-                "is a method member"
-            ) from e
-        else:
-            if not is_callable:
-                cls.__non_callable_proto_members__.add(attr)
+    cls.__non_callable_proto_members_cache__ = None
    return cls



diff --git a/Misc/NEWS.d/next/Library/2025-04-16-06-50-13.gh-issue-132493.XvnL7t.rst b/Misc/NEWS.d/next/Library/2025-04-16-06-50-13.gh-issue-132493.XvnL7t.rst
@@ -0,0 +1 @@
+Speed up the creation of :class:`typing.Protocol` subclasses.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Speed up the creation of :class:`typing.Protocol` subclasses.
JelleZijlstra marked this conversation as resolved. Show resolved Hide resolved