Added empty option to clone utility method.

benedict/core/clone.py

@@ -3,5 +3,8 @@
 import copy
 
 
-def clone(obj):
+def clone(obj, empty=False):
-    return copy.deepcopy(obj)
+    d = copy.deepcopy(obj)
+    if empty:
+        d.clear()
+    return d

benedict/core/filter.py

@@ -1,11 +1,12 @@
 # -*- coding: utf-8 -*-
 
+from benedict.core import clone
+
 
 def filter(d, predicate):
     if not callable(predicate):
         raise ValueError('predicate argument must be a callable.')
-    new_dict = d.copy()
+    new_dict = clone(d, empty=True)
-    new_dict.clear()
     keys = list(d.keys())
     for key in keys:
         value = d.get(key, None)

benedict/core/flatten.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 
+from benedict.core import clone
 from benedict.utils import type_util
 
 
@@ -10,8 +11,7 @@ def _flatten_key(base_key, key, separator):
 
 
 def flatten(d, separator='_', **kwargs):
-    new_dict = d.copy()
+    new_dict = clone(d, empty=True)
-    new_dict.clear()
     keys = list(d.keys())
     base_key = kwargs.pop('base_key', '')
     for key in keys:

benedict/core/invert.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 
+from benedict.core import clone
 from benedict.utils import type_util
 
 
@@ -16,8 +17,7 @@ def _invert_list(d, key, value, flat):
 
 
 def invert(d, flat=False):
-    new_dict = d.copy()
+    new_dict = clone(d, empty=True)
-    new_dict.clear()
     for key, value in d.items():
         if type_util.is_list_or_tuple(value):
             _invert_list(new_dict, key, value, flat)

benedict/core/subset.py

@@ -1,11 +1,11 @@
 # -*- coding: utf-8 -*-
 
+from benedict.core import clone
 from benedict.utils import type_util
 
 
 def subset(d, keys, *args):
-    new_dict = d.copy()
+    new_dict = clone(d, empty=True)
-    new_dict.clear()
     if type_util.is_string(keys):
         keys = [keys]
     keys += args

benedict/core/unflatten.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 
+from benedict.core import clone
 from benedict.dicts.keylist import keylist_util
 from benedict.utils import type_util
 
@@ -12,8 +13,7 @@ def _unflatten_item(key, value, separator):
 
 
 def unflatten(d, separator='_'):
-    new_dict = d.copy()
+    new_dict = clone(d, empty=True)
-    new_dict.clear()
     keys = list(d.keys())
     for key in keys:
         value = d.get(key, None)

tests/core/test_clone.py

@@ -22,3 +22,15 @@ class clone_test_case(unittest.TestCase):
         o['a']['b']['c'] = 2
         self.assertEqual(i['a']['b']['c'], 1)
         self.assertEqual(o['a']['b']['c'], 2)
+
+    def test_clone_empty(self):
+        i = {
+            'a': {
+                'b': {
+                    'c': 1
+                }
+            }
+        }
+        o = _clone(i, empty=True)
+        self.assertEqual(type(i), type(o))
+        self.assertEqual(o, {})