Added as_pure_dictionary method for proper pickling and unpickling of…

… recursive UltraDict instances (#25)

UltraDict.py

@@ -1103,6 +1103,19 @@ def unlink_by_name(name, ignore_errors=False):
                 raise e
         return False
 
+    @classmethod
+    def as_pure_dictionary(cls, to_convert=None):
+        if to_convert is None:
+            to_convert = cls
+
+        if isinstance(to_convert, UltraDict):
+            res = dict(to_convert)
+            for key in res.keys():
+                res[key] = cls.as_pure_dictionary(res[key])
+
+            return res
+
+        return to_convert
 
 
 # Saved as a reference

tests/tests.py

@@ -179,6 +179,58 @@ def test_example_recover_from_stale_lock(self):
         self.assertEqual(ret.stdout.splitlines()[-1], b"Counter: 100 == 100", self.exec_show_output(ret))
 
 
+    def test_export_as_pure_dict(self):
+        ultra = UltraDict(
+            {
+                "1": "hello",
+                "2": 5,
+                "3": {
+                    "1": 1,
+                    "2": {
+                        "1": True,
+                        "2": None,
+                        "3": [1, 2, 3]
+                    },
+                    "3": [4, 5, 6, {"7": 8}]
+                }
+            },
+            recurse=True
+        )
+
+        ultra2 = UltraDict(
+            {
+                "1": "hello",
+                "2": 5,
+                "3": {
+                    "1": 1,
+                    "2": {
+                        "1": True,
+                        "2": None,
+                        "3": [1, 2, 3]
+                    },
+                    "3": [4, 5, 6, {"7": 8}]
+                }
+            },
+            recurse=False
+        )
+
+
+        def assert_pure_dict(elem):
+            self.assertNotIsInstance(elem, UltraDict)
+
+            if isinstance(elem, dict):
+                for key in elem.keys():
+                    assert_pure_dict(elem[key])
+
+
+        with self.assertRaises(AssertionError):
+            assert_pure_dict(ultra)
+            assert_pure_dict(ultra2)
+
+        assert_pure_dict(ultra.as_pure_dictionary())
+        assert_pure_dict(ultra2.as_pure_dictionary())
+
+
 if __name__ == '__main__':
     if len(sys.argv) > 1:
         for i in range(0, len(sys.argv)):