python · AlexWaygood · Apr 5, 2023 · Mar 31, 2023 · Apr 1, 2023 · Apr 1, 2023
@@ -1905,7 +1905,8 @@ class _TypingEllipsis:

 _TYPING_INTERNALS = frozenset({
    '__parameters__', '__orig_bases__',  '__orig_class__',
-    '_is_protocol', '_is_runtime_protocol'
+    '_is_protocol', '_is_runtime_protocol', '__protocol_attrs__',
+    '__callable_proto_members_only__',
 })

 _SPECIAL_NAMES = frozenset({
@@ -1935,11 +1936,6 @@ def _get_protocol_attrs(cls):
    return attrs


-def _is_callable_members_only(cls, protocol_attrs):
-    # PEP 544 prohibits using issubclass() with protocols that have non-method members.
-    return all(callable(getattr(cls, attr, None)) for attr in protocol_attrs)
-
-
 def _no_init_or_replace_init(self, *args, **kwargs):
    cls = type(self)

@@ -2001,6 +1997,14 @@ def _allow_reckless_class_checks(depth=3):
 class _ProtocolMeta(ABCMeta):
    # This metaclass is really unfortunate and exists only because of
    # the lack of __instancehook__.
+    def __init__(cls, *args, **kwargs):
+        cls.__protocol_attrs__ = _get_protocol_attrs(cls)
+        # PEP 544 prohibits using issubclass()
+        # with protocols that have non-method members.
+        cls.__callable_proto_members_only__ = all(
+            callable(getattr(cls, attr, None)) for attr in cls.__protocol_attrs__
+        )
+
    def __instancecheck__(cls, instance):
        # We need this method for situations where attributes are
        # assigned in __init__.
@@ -2016,20 +2020,15 @@ def __instancecheck__(cls, instance):
        if not is_protocol_cls and issubclass(instance.__class__, cls):
            return True

-        protocol_attrs = _get_protocol_attrs(cls)
-
-        if (
-            _is_callable_members_only(cls, protocol_attrs)
-            and issubclass(instance.__class__, cls)
-        ):
+        if cls.__callable_proto_members_only__ and issubclass(instance.__class__, cls):
            return True

        if is_protocol_cls:
            if all(hasattr(instance, attr) and
                    # All *methods* can be blocked by setting them to None.
                    (not callable(getattr(cls, attr, None)) or
                     getattr(instance, attr) is not None)
-                    for attr in protocol_attrs):
+                    for attr in cls.__protocol_attrs__):
                return True
        return super().__instancecheck__(instance)

@@ -2087,9 +2086,7 @@ def _proto_hook(other):
                raise TypeError("Instance and class checks can only be used with"
                                " @runtime_checkable protocols")

-            protocol_attrs = _get_protocol_attrs(cls)
-
-            if not _is_callable_members_only(cls, protocol_attrs):
+            if not cls.__callable_proto_members_only__ :
                if _allow_reckless_class_checks():
                    return NotImplemented
                raise TypeError("Protocols with non-method members"
@@ -2099,7 +2096,7 @@ def _proto_hook(other):
                raise TypeError('issubclass() arg 1 must be a class')

            # Second, perform the actual structural compatibility check.
-            for attr in protocol_attrs:
+            for attr in cls.__protocol_attrs__:
                for base in other.__mro__:
                    # Check if the members appears in the class dictionary...
                    if attr in base.__dict__: