copy: support frozendict

Author: vstinner

Lib/copy.py

@@ -105,7 +105,7 @@ def copy(x):
           types.BuiltinFunctionType, types.EllipsisType,
           types.NotImplementedType, types.FunctionType, types.CodeType,
           weakref.ref, super})
-_copy_builtin_containers = frozenset({list, dict, set, bytearray})
+_copy_builtin_containers = frozenset({list, dict, frozendict, set, bytearray})
 
 def deepcopy(x, memo=None):
     """Deep copy operation on arbitrary Python objects.
@@ -203,6 +203,11 @@ def _deepcopy_dict(x, memo, deepcopy=deepcopy):
     return y
 d[dict] = _deepcopy_dict
 
+def _deepcopy_frozendict(x, memo, deepcopy=deepcopy):
+    y = _deepcopy_dict(x, memo, deepcopy)
+    return frozendict(y)
+d[frozendict] = _deepcopy_frozendict
+
 def _deepcopy_method(x, memo): # Copy instance methods
     return type(x)(x.__func__, deepcopy(x.__self__, memo))
 d[types.MethodType] = _deepcopy_method

Lib/test/test_copy.py

@@ -133,6 +133,18 @@ def test_copy_dict(self):
         self.assertEqual(y, x)
         self.assertIsNot(y, x)
 
+    def test_copy_frozendict(self):
+        x = frozendict(foo=1, bar=2)
+        y = copy.copy(x)
+        self.assertEqual(y, x)
+        self.assertEqual(type(y), frozendict)
+        self.assertIsNot(y, x)
+        x = frozendict()
+        y = copy.copy(x)
+        self.assertEqual(y, x)
+        self.assertEqual(type(y), frozendict)
+        self.assertIsNot(y, x)
+
     def test_copy_set(self):
         x = {1, 2, 3}
         y = copy.copy(x)