add explicit items()/keys()/values() methods

immutabledict/__init__.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from collections import OrderedDict
-from typing import Any, Dict, Iterable, Iterator, Mapping, Optional, Type, TypeVar
+from typing import Any, Dict, ItemsView, Iterable, Iterator, Mapping, Optional, Type, TypeVar, ValuesView, KeysView
 
 __version__ = "3.0.0"
 
@@ -73,6 +73,15 @@ def __ror__(self, other: Any) -> Dict[Any, Any]:
     def __ior__(self, other: Any) -> immutabledict[_K, _V]:
         raise TypeError(f"'{self.__class__.__name__}' object is not mutable")
 
+    def items(self) -> ItemsView[_K, _V]:
+        return self._dict.items()
+
+    def keys(self) -> KeysView[_K]:
+        return self._dict.keys()
+
+    def values(self) -> ValuesView[_V]:
+        return self._dict.values()
+
 
 class ImmutableOrderedDict(immutabledict[_K, _V]):
     """

tests/test_immutabledict.py

@@ -185,6 +185,19 @@ def test_union_operator_update_with_dict_second(self) -> None:
         assert first_dict == {"a": "a", "b": "b"}
         assert second_dict == {"a": "A", "c": "c"}
 
+    def test_performance(self) -> None:
+        from timeit import timeit
+        time_standard = timeit(
+            "for k, v in d.items(): s += 1", number=3,
+            setup="s=0; d = {i:i for i in range(1000000)}")
+
+        time_immutable = timeit(
+            "for k, v in d.items(): s += 1", globals=globals(), number=3,
+            setup="s=0; d = immutabledict({i:i for i in range(1000000)})")
+
+        assert time_immutable < 1.2 * time_standard
+
+
 
 class TestImmutableOrderedDict:
     def test_ordered(self) -> None: