gh-141647: attribute breaks __eq__ behaviour of IPv4Network and IPv6Network

Lib/ipaddress.py

@@ -567,11 +567,10 @@ def __int__(self):
         return self._ip
 
     def __eq__(self, other):
-        try:
-            return (self._ip == other._ip
-                    and self.version == other.version)
-        except AttributeError:
+        if not isinstance(other, _BaseAddress):
             return NotImplemented
+        return (self._ip == other._ip
+                and self.version == other.version)
 
     def __lt__(self, other):
         if not isinstance(other, _BaseAddress):
@@ -718,12 +717,11 @@ def __lt__(self, other):
         return False
 
     def __eq__(self, other):
-        try:
-            return (self.version == other.version and
-                    self.network_address == other.network_address and
-                    int(self.netmask) == int(other.netmask))
-        except AttributeError:
+        if not isinstance(other, _BaseNetwork):
             return NotImplemented
+        return (self.version == other.version
+                and self.network_address == other.network_address
+                and int(self.netmask) == int(other.netmask))
 
     def __hash__(self):
         return hash((int(self.network_address), int(self.netmask)))

Lib/test/test_ipaddress.py

@@ -1078,6 +1078,41 @@ def test_incompatible_versions(self):
         self.assertRaises(TypeError, v6net_scoped.__lt__, v4net)
         self.assertRaises(TypeError, v6net_scoped.__gt__, v4net)
 
+    def test_address_eq_with_faux_object(self):
+        class AlwaysTrue:
+            def __init__(self, ip_value):
+                self._ip = ip_value
+                self.version = 42
+
+            def __eq__(self, other):
+                return True
+
+        addr4 = ipaddress.IPv4Address('192.168.1.1')
+        always_true4 = AlwaysTrue(addr4._ip)
+        self.assertEqual(addr4, always_true4)
+
+        addr6 = ipaddress.IPv6Address('::1')
+        always_true6 = AlwaysTrue(addr6._ip)
+        self.assertEqual(addr6, always_true6)
+
+        intf4 = ipaddress.IPv4Interface('192.168.1.1/24')
+        always_true_intf4 = AlwaysTrue(intf4._ip)
+        self.assertEqual(intf4, always_true_intf4)
+
+        intf6 = ipaddress.IPv6Interface('::1/128')
+        always_true_intf6 = AlwaysTrue(intf6._ip)
+        self.assertEqual(intf6, always_true_intf6)
+
+    def test_network_eq_with_faux_object(self):
+        class AlwaysTrue:
+            version = 42
+            def __eq__(self, other):
+                return True
+
+        always_true = AlwaysTrue()
+        self.assertEqual(ipaddress.IPv4Network('43.48.0.0/12'), always_true)
+        self.assertEqual(ipaddress.IPv6Network('::eeff:ae3f:d473/128'), always_true)
+
 
 class IpaddrUnitTest(unittest.TestCase):
 

Misc/NEWS.d/next/Library/2025-11-17-17-06-56.gh-issue-131647.tyafol.rst

@@ -0,0 +1,4 @@
+:mod:`ipaddress`: fix equality testing for :class:`~ipaddress.IPv4Address`,
+:class:`~ipaddress.IPv6Address`, :class:`~ipaddress.IPv4Network`, and
+:class:`~ipaddress.IPv6Network` to avoid comparing instances of incorrect
+types.