bpo-35540 dataclasses.asdict now supports defaultdict fields (gh-32056)

1 files changed, 8 insertions, 0 deletions

diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py
index 65fb8f2..bf7f290 100644
--- a/Lib/dataclasses.py
+++ b/Lib/dataclasses.py
@@ -1325,6 +1325,14 @@ def _asdict_inner(obj, dict_factory):
         # generator (which is not true for namedtuples, handled
         # above).
         return type(obj)(_asdict_inner(v, dict_factory) for v in obj)
+    elif isinstance(obj, dict) and hasattr(type(obj), 'default_factory'):
+        # obj is a defaultdict, which has a different constructor from
+        # dict as it requires the default_factory as its first arg.
+        # https://bugs.python.org/issue35540
+        result = type(obj)(getattr(obj, 'default_factory'))
+        for k, v in obj.items():
+            result[_asdict_inner(k, dict_factory)] = _asdict_inner(v, dict_factory)
+        return result
     elif isinstance(obj, dict):
         return type(obj)((_asdict_inner(k, dict_factory),
                           _asdict_inner(v, dict_factory))