New submission from Will T <timwillo...@gmail.com>:
_asdict_inner attempts to manually recursively deepcopy dicts by calling type(obj) with a generator of transformed keyvalue tuples @ https://github.com/python/cpython/blob/b2f642ccd2f65d2f3bf77bbaa103dd2bc2733734/Lib/dataclasses.py#L1080 . defaultdicts are dicts so this runs but unlike other dicts their first arg has to be a callable or None: import collections import dataclasses as dc @dc.dataclass() class C: d: dict c = C(collections.defaultdict(lambda: 3, {})) d = dc.asdict(c) assert isinstance(d['d'], collections.defaultdict) assert d['d']['a'] == 3 => Traceback (most recent call last): File "boom.py", line 9, in <module> d = dc.asdict(c) File "/Users/spinlock/.pyenv/versions/3.7.1/lib/python3.7/dataclasses.py", line 1019, in asdict return _asdict_inner(obj, dict_factory) File "/Users/spinlock/.pyenv/versions/3.7.1/lib/python3.7/dataclasses.py", line 1026, in _asdict_inner value = _asdict_inner(getattr(obj, f.name), dict_factory) File "/Users/spinlock/.pyenv/versions/3.7.1/lib/python3.7/dataclasses.py", line 1058, in _asdict_inner for k, v in obj.items()) TypeError: first argument must be callable or None I understand that it isn't this bit of code's job to support every dict (and list etc.) subclass under the sun but given defaultdict is stdlib it's imo worth supporting explicitly. ---------- components: Library (Lib) messages: 332166 nosy: wrmsr priority: normal severity: normal status: open title: dataclasses.asdict breaks with defaultdict fields versions: Python 3.7 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue35540> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
