add set/delete/update functions (#271)

immutabledict/__init__.py

@@ -98,6 +98,21 @@ def keys(self) -> KeysView[_K]:
     def values(self) -> ValuesView[_V]:
         return self._dict.values()
 
+    def set(self, key: _K, value: Any) -> immutabledict[_K, _V]:
+        new = dict(self._dict)
+        new[key] = value
+        return self.__class__(new)
+
+    def delete(self, key: _K) -> immutabledict[_K, _V]:
+        new = dict(self._dict)
+        del new[key]
+        return self.__class__(new)
+
+    def update(self, _dict: Dict[_K, _V]) -> immutabledict[_K, _V]:
+        new = dict(self._dict)
+        new.update(_dict)
+        return self.__class__(new)
+
 
 class ImmutableOrderedDict(immutabledict[_K, _V]):
     """

tests/test_immutabledict.py

@@ -215,6 +215,24 @@ def test_performance(self, statement: str) -> None:
 
         assert time_immutable < 1.2 * time_standard
 
+    def test_set_delete_update(self) -> None:
+        d: immutabledict[str, int] = immutabledict(a=1, b=2)
+
+        assert d.set("a", 10) == immutabledict(a=10, b=2) == dict(a=10, b=2)
+        assert d.delete("a") == immutabledict(b=2) == dict(b=2)
+
+        with pytest.raises(KeyError):
+            d.delete("c")
+
+        assert d.update({"a": 3}) == immutabledict(a=3, b=2) == dict(a=3, b=2)
+
+        assert (
+            d.update({"c": 17}) == immutabledict(a=1, b=2, c=17) == dict(a=1, b=2, c=17)
+        )
+
+        # Make sure d doesn't change
+        assert d == immutabledict(a=1, b=2) == dict(a=1, b=2)
+
     def test_new_kwargs(self) -> None:
         immutable_dict: immutabledict[str, int] = immutabledict(a=1, b=2)
         assert immutable_dict == {"a": 1, "b": 2} == dict(a=1, b=2)