Allow to replace nested tuple and list via options (#731)

* Allow to replace nested tuple and list via options

* Add comments

* Fix single nested items

* Simplify the code

* Simplify the code

* Simplify the code

* Simplify the code

* Update docstring

* Update docstring

* Support quotation mark

* modify docstring

mmcv/utils/config.py

@@ -488,8 +488,10 @@ class Config:
 class DictAction(Action):
     """
     argparse action to split an argument into KEY=VALUE form
-    on the first = and append to a dictionary. List options should
-    be passed as comma separated values, i.e KEY=V1,V2,V3
+    on the first = and append to a dictionary. List options can
+    be passed as comma separated values, i.e 'KEY=V1,V2,V3', or with explicit
+    brackets, i.e. 'KEY=[V1,V2,V3]'. It also support nested brackets to build
+    list/tuple values. e.g. 'KEY=[(V1,V2),(V3,V4)]'
     """
 
     @staticmethod
@@ -506,12 +508,72 @@ class DictAction(Action):
             return True if val.lower() == 'true' else False
         return val
 
+    @staticmethod
+    def _parse_iterable(val):
+        """Parse iterable values in the string.
+
+        All elements inside '()' or '[]' are treated as iterable values.
+
+        Args:
+            val (str): Value string.
+
+        Returns:
+            list | tuple: The expanded list or tuple from the string.
+
+        Examples:
+            >>> DictAction._parse_iterable('1,2,3')
+            [1, 2, 3]
+            >>> DictAction._parse_iterable('[a, b, c]')
+            ['a', 'b', 'c']
+            >>> DictAction._parse_iterable('[(1, 2, 3), [a, b], c]')
+            [(1, 2, 3), ['a', 'b], 'c']
+        """
+
+        def find_next_comma(string):
+            """Find the position of next comma in the string.
+
+            If no ',' is found in the string, return the string length. All
+            chars inside '()' and '[]' are treated as one element and thus ','
+            inside these brackets are ignored.
+            """
+            assert (string.count('(') == string.count(')')) and (
+                    string.count('[') == string.count(']')), \
+                f'Imbalanced brackets exist in {string}'
+            end = len(string)
+            for idx, char in enumerate(string):
+                pre = string[:idx]
+                # The string before this ',' is balanced
+                if ((char == ',') and (pre.count('(') == pre.count(')'))
+                        and (pre.count('[') == pre.count(']'))):
+                    end = idx
+                    break
+            return end
+
+        # Strip ' and " characters and replace whitespace.
+        val = val.strip('\'\"').replace(' ', '')
+        is_tuple = False
+        if val.startswith('(') and val.endswith(')'):
+            is_tuple = True
+            val = val[1:-1]
+        elif val.startswith('[') and val.endswith(']'):
+            val = val[1:-1]
+        elif ',' not in val:
+            # val is a single value
+            return DictAction._parse_int_float_bool(val)
+
+        values = []
+        while len(val) > 0:
+            comma_idx = find_next_comma(val)
+            element = DictAction._parse_iterable(val[:comma_idx])
+            values.append(element)
+            val = val[comma_idx + 1:]
+        if is_tuple:
+            values = tuple(values)
+        return values
+
     def __call__(self, parser, namespace, values, option_string=None):
         options = {}
         for kv in values:
             key, val = kv.split('=', maxsplit=1)
-            val = [self._parse_int_float_bool(v) for v in val.split(',')]
-            if len(val) == 1:
-                val = val[0]
-            options[key] = val
+            options[key] = self._parse_iterable(val)
         setattr(namespace, self.dest, options)

tests/test_utils/test_config.py

@@ -347,11 +347,23 @@ def test_dict_action():
     parser = argparse.ArgumentParser(description='Train a detector')
     parser.add_argument(
         '--options', nargs='+', action=DictAction, help='custom options')
+    # Nested brackets
+    args = parser.parse_args(
+        ['--options', 'item2.a=a,b', 'item2.b=[(a,b), [1,2], false]'])
+    out_dict = {'item2.a': ['a', 'b'], 'item2.b': [('a', 'b'), [1, 2], False]}
+    assert args.options == out_dict
+    # Single Nested brackets
+    args = parser.parse_args(['--options', 'item2.a=[[1]]'])
+    out_dict = {'item2.a': [[1]]}
+    assert args.options == out_dict
+    # Imbalance bracket
+    with pytest.raises(AssertionError):
+        parser.parse_args(['--options', 'item2.a=[(a,b), [1,2], false'])
+    # Normal values
     args = parser.parse_args(
         ['--options', 'item2.a=1', 'item2.b=0.1', 'item2.c=x', 'item3=false'])
     out_dict = {'item2.a': 1, 'item2.b': 0.1, 'item2.c': 'x', 'item3': False}
     assert args.options == out_dict
-
     cfg_file = osp.join(data_path, 'config/a.py')
     cfg = Config.fromfile(cfg_file)
     cfg.merge_from_dict(args.options)