Support deepcopy for Config (#1658)

* Support deepcopy for Config

* Iterate the `__dict__` of Config directly.

* Use __new__ to avoid unnecessary initialization.

* Improve according to comments

mmcv/utils/config.py

@@ -528,6 +528,16 @@ class Config:
     def __getstate__(self):
         return (self._cfg_dict, self._filename, self._text)
 
+    def __deepcopy__(self, memo):
+        cls = self.__class__
+        other = cls.__new__(cls)
+        memo[id(self)] = other
+
+        for key, value in self.__dict__.items():
+            super(Config, other).__setattr__(key, copy.deepcopy(value, memo))
+
+        return other
+
     def __setstate__(self, state):
         _cfg_dict, _filename, _text = state
         super(Config, self).__setattr__('_cfg_dict', _cfg_dict)

tests/test_utils/test_config.py

 # Copyright (c) OpenMMLab. All rights reserved.
 import argparse
+import copy
 import json
 import os
 import os.path as osp
@@ -536,3 +537,15 @@ def test_deprecation():
         with pytest.warns(DeprecationWarning):
             cfg = Config.fromfile(cfg_file)
         assert cfg.item1 == 'expected'
+
+
+def test_deepcopy():
+    cfg_file = osp.join(data_path, 'config/n.py')
+    cfg = Config.fromfile(cfg_file)
+    new_cfg = copy.deepcopy(cfg)
+
+    assert isinstance(new_cfg, Config)
+    assert new_cfg._cfg_dict == cfg._cfg_dict
+    assert new_cfg._cfg_dict is not cfg._cfg_dict
+    assert new_cfg._filename == cfg._filename
+    assert new_cfg._text == cfg._text