pythonnet · filmor · Apr 18, 2026 · Apr 19, 2026
diff --git a/src/runtime/InteropConfiguration.cs b/src/runtime/InteropConfiguration.cs
@@ -22,6 +22,7 @@ public static InteropConfiguration MakeDefault()
                 {
                     DefaultBaseTypeProvider.Instance,
                     new CollectionMixinsProvider(new Lazy<PyObject>(() => Py.Import("clr._extras.collections"))),
+                    new DynamicObjectMixinsProvider(new Lazy<PyObject>(() => Py.Import("clr._extras.dlr"))),
                 },
             };
         }

diff --git a/src/runtime/Mixins/DynamicObjectMixinsProvider.cs b/src/runtime/Mixins/DynamicObjectMixinsProvider.cs
@@ -0,0 +1,47 @@
+using System;
+using System.Collections.Generic;
+using System.Dynamic;
+
+namespace Python.Runtime.Mixins;
+
+class DynamicObjectMixinsProvider : IPythonBaseTypeProvider, IDisposable
+{
+    readonly Lazy<PyObject> mixinsModule;
+
+    public DynamicObjectMixinsProvider(Lazy<PyObject> mixinsModule) =>
+		this.mixinsModule = mixinsModule ?? throw new ArgumentNullException(nameof(mixinsModule));
+
+    public PyObject Mixins => mixinsModule.Value;
+
+    public IEnumerable<PyType> GetBaseTypes(Type type, IList<PyType> existingBases)
+    {
+        if (type is null)
+            throw new ArgumentNullException(nameof(type));
+
+        if (existingBases is null)
+            throw new ArgumentNullException(nameof(existingBases));
+
+        if (!typeof(IDynamicMetaObjectProvider).IsAssignableFrom(type))
+            return existingBases;
+
+        var newBases = new List<PyType>(existingBases)
+        {
+            new(Mixins.GetAttr("DynamicMetaObjectProviderMixin"))
+        };
+
+        if (type.IsInterface && type.BaseType is null)
+        {
+            newBases.RemoveAll(@base => PythonReferenceComparer.Instance.Equals(@base, Runtime.PyBaseObjectType));
+        }
+
+        return newBases;
+    }
+
+    public void Dispose()
+    {
+        if (this.mixinsModule.IsValueCreated)
+        {
+            this.mixinsModule.Value.Dispose();
+        }
+    }
+}
diff --git a/src/runtime/Mixins/dlr.py b/src/runtime/Mixins/dlr.py
@@ -0,0 +1,16 @@
+"""
+Implements helpers for Dynamic Language Runtime (DLR) types.
+"""
+
+class DynamicMetaObjectProviderMixin:
+    def __dir__(self):
+        names = set(super().__dir__())
+
+        get_names = getattr(self, "GetDynamicMemberNames", None)
+        if callable(get_names):
+            try:
+                names.update(get_names())
+            except Exception:
+                pass
+
+        return list(sorted(names))
diff --git a/src/runtime/PythonEngine.cs b/src/runtime/PythonEngine.cs
@@ -299,7 +299,7 @@ static void LoadSubmodule(BorrowedReference targetModuleDict, string fullName, s
 
         static void LoadMixins(BorrowedReference targetModuleDict)
         {
-            foreach (string nested in new[] { "collections" })
+            foreach (string nested in new[] { "collections", "dlr" })
             {
                 LoadSubmodule(targetModuleDict,
                     fullName: "clr._extras." + nested,

diff --git a/src/runtime/Runtime.cs b/src/runtime/Runtime.cs
@@ -151,6 +151,7 @@ internal static void Initialize(bool initSigs = false)
 
             GenericUtil.Reset();
             ClassManager.Reset();
+            ClassBase.Reset();
             ClassDerivedObject.Reset();
             TypeManager.Initialize();
             CLRObject.creationBlocked = false;
@@ -280,6 +281,7 @@ internal static void Shutdown()
 
             NullGCHandles(ExtensionType.loadedExtensions);
             ClassManager.RemoveClasses();
+            ClassBase.Reset();
             TypeManager.RemoveTypes();
             _typesInitialized = false;
 

diff --git a/src/runtime/Types/ClassBase.cs b/src/runtime/Types/ClassBase.cs
@@ -2,6 +2,7 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Dynamic;
 using System.Linq;
 using System.Reflection;
 using System.Runtime.InteropServices;
@@ -22,6 +23,10 @@ namespace Python.Runtime
     [Serializable]
     internal class ClassBase : ManagedType, IDeserializationCallback
     {
+        static readonly DynamicObjectMemberAccessor dynamicMemberAccessor = new();
+
+        internal static void Reset() => dynamicMemberAccessor.Clear();
+
         [NonSerialized]
         internal List<string> dotNetMembers = new();
         internal Indexer? indexer;
@@ -603,6 +608,105 @@ static IEnumerable<MethodInfo> GetCallImplementations(Type type)
             => type.GetMethods(BindingFlags.Public | BindingFlags.Instance)
                 .Where(m => m.Name == "__call__");
 
+        static NewReference tp_getattro_dlr(BorrowedReference ob, BorrowedReference key)
+        {
+            var attr = Runtime.PyObject_GenericGetAttr(ob, key);
+            if (!attr.IsNull())
+            {
+                return attr;
+            }
+
+            // Only run the DLR binder if the error was AttributeError, otherwise preserve the original error
+            if (Runtime.PyErr_ExceptionMatches(Exceptions.AttributeError) == 0)
+            {
+                return default;
+            }
+
+            if (!Runtime.PyString_Check(key))
+            {
+                return default;
+            }
+
+            if (GetManagedObject(ob) is not CLRObject co)
+            {
+                return default;
+            }
+
+            // Slot registration already guarantees this type supports DLR
+            var dynamicObject = (IDynamicMetaObjectProvider)co.inst;
+
+            string? memberName = Runtime.GetManagedString(key);
+            if (memberName is null)
+            {
+                return default;
+            }
+
+            if (!dynamicMemberAccessor.TryGetMember(dynamicObject, memberName, out object? value))
+            {
+                return default;
+            }
+
+            // Clear the lingering AttributeError
+            Runtime.PyErr_Clear();
+
+            using var pyValue = value.ToPython();
+            return pyValue.NewReferenceOrNull();
+        }
+
+        static int tp_setattro_dlr(BorrowedReference ob, BorrowedReference key, BorrowedReference val)
+        {
+            int result = Runtime.PyObject_GenericSetAttr(ob, key, val);
+            if (result == 0)
+            {
+                return 0;
+            }
+
+            // Preserve non-attribute errors exactly as they are.
+            if (Runtime.PyErr_ExceptionMatches(Exceptions.AttributeError) == 0)
+            {
+                return -1;
+            }
+
+            // Deletion fallback is intentionally not handled by DLR binder yet.
+            if (val == null)
+            {
+                return -1;
+            }
+
+            if (!Runtime.PyString_Check(key))
+            {
+                return -1;
+            }
+
+            if (GetManagedObject(ob) is not CLRObject co)
+            {
+                return -1;
+            }
+
+            // Slot registration already guarantees this type supports DLR.
+            var dynamicObject = (IDynamicMetaObjectProvider)co.inst;
+
+            string? memberName = Runtime.GetManagedString(key);
+            if (memberName is null)
+            {
+                return -1;
+            }
+
+            if (!Converter.ToManaged(val, typeof(object), out object? managedValue, true))
+            {
+                return -1;
+            }
+
+            if (!dynamicMemberAccessor.TrySetMember(dynamicObject, memberName, managedValue))
+            {
+                return -1;
+            }
+
+            // Clear the lingering AttributeError
+            Runtime.PyErr_Clear();
+            return 0;
+        }
+
         public virtual void InitializeSlots(BorrowedReference pyType, SlotsHolder slotsHolder)
         {
             if (!this.type.Valid) return;
@@ -612,6 +716,12 @@ public virtual void InitializeSlots(BorrowedReference pyType, SlotsHolder slotsH
                 TypeManager.InitializeSlotIfEmpty(pyType, TypeOffset.tp_call, new Interop.BBB_N(tp_call_impl), slotsHolder);
             }
 
+            if (typeof(IDynamicMetaObjectProvider).IsAssignableFrom(this.type.Value))
+            {
+                TypeManager.InitializeSlotIfEmpty(pyType, TypeOffset.tp_getattro, new Interop.BB_N(tp_getattro_dlr), slotsHolder);
+                TypeManager.InitializeSlotIfEmpty(pyType, TypeOffset.tp_setattro, new Interop.BBB_I32(tp_setattro_dlr), slotsHolder);
+            }
+
             if (indexer is not null)
             {
                 if (indexer.CanGet)

diff --git a/src/runtime/Types/ClassDerived.cs b/src/runtime/Types/ClassDerived.cs
@@ -40,7 +40,7 @@ static ClassDerivedObject()
             moduleBuilders = new Dictionary<Tuple<string, string>, ModuleBuilder>();
         }
 
-        public static void Reset()
+        public static new void Reset()
         {
             assemblyBuilders = new Dictionary<string, AssemblyBuilder>();
             moduleBuilders = new Dictionary<Tuple<string, string>, ModuleBuilder>();

diff --git a/src/runtime/Types/DynamicObjectMemberAccessor.cs b/src/runtime/Types/DynamicObjectMemberAccessor.cs
@@ -0,0 +1,84 @@
+using System;
+using System.Dynamic;
+using System.Runtime.CompilerServices;
+using Microsoft.CSharp.RuntimeBinder;
+
+namespace Python.Runtime;
+
+class DynamicObjectMemberAccessor
+{
+    const int MaxCacheEntries = 1000;
+
+    readonly ConcurrentLruCache<MemberKey, Func<object, object>> getters = new(MaxCacheEntries);
+    readonly ConcurrentLruCache<MemberKey, Action<object, object?>> setters = new(MaxCacheEntries);
+
+    static readonly CSharpArgumentInfo[] getArgumentInfo =
+    {
+        CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null),
+    };
+
+    static readonly CSharpArgumentInfo[] setArgumentInfo =
+    {
+        CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null),
+        CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null),
+    };
+
+    public bool TryGetMember(IDynamicMetaObjectProvider obj, string memberName, out object? value)
+    {
+        if (obj is null)
+            throw new ArgumentNullException(nameof(obj));
+        if (memberName is null)
+            throw new ArgumentNullException(nameof(memberName));
+
+        var getter = getters.GetOrAdd(new MemberKey(obj.GetType(), memberName), static key =>
+        {
+            var binder = Binder.GetMember(CSharpBinderFlags.None, key.MemberName, key.Type, getArgumentInfo);
+            var callSite = CallSite<Func<CallSite, object, object>>.Create(binder);
+            return obj => callSite.Target(callSite, obj);
+        });
+
+        try
+        {
+            value = getter(obj);
+            return true;
+        }
+        catch (RuntimeBinderException)
+        {
+            value = null;
+            return false;
+        }
+    }
+
+    public bool TrySetMember(IDynamicMetaObjectProvider obj, string memberName, object? value)
+    {
+        if (obj is null)
+            throw new ArgumentNullException(nameof(obj));
+        if (memberName is null)
+            throw new ArgumentNullException(nameof(memberName));
+
+        var setter = setters.GetOrAdd(new MemberKey(obj.GetType(), memberName), static key =>
+        {
+            var binder = Binder.SetMember(CSharpBinderFlags.None, key.MemberName, key.Type, setArgumentInfo);
+            var callSite = CallSite<Action<CallSite, object, object?>>.Create(binder);
+            return (obj, value) => callSite.Target(callSite, obj, value);
+        });
+
+        try
+        {
+            setter(obj, value);
+            return true;
+        }
+        catch (RuntimeBinderException)
+        {
+            return false;
+        }
+    }
+
+    readonly record struct MemberKey(Type Type, string MemberName);
+
+    public void Clear()
+    {
+        getters.Clear();
+        setters.Clear();
+    }
+}
-Original file line number
+Diff line change
@@ Expand Up / @@ -22,6 +22,7 @@ public static InteropConfiguration MakeDefault() @@
                     {
                         DefaultBaseTypeProvider.Instance,
                         new CollectionMixinsProvider(new Lazy<PyObject>(() => Py.Import("clr._extras.collections"))),
+                        new DynamicObjectMixinsProvider(new Lazy<PyObject>(() => Py.Import("clr._extras.dlr"))),
                     },
                 };
             }
@@ Expand Down @@