This issue tracker has been migrated to GitHub, and is currently read-only.
For more information, see the GitHub FAQs in the Python's Developer Guide.

Author eric.smith
Recipients eric.smith, rhettinger
Date 2018-02-25.22:29:23
SpamBayes Score -1.0
Marked as misclassified Yes
Message-id <>
A related issue is that dataclasses derived from frozen dataclasses are automatically "promoted" to being frozen.

>>> @dataclass(frozen=True)
... class A:
...     i: int
>>> @dataclass
... class B(A):
...     j: int
>>> b = B(1, 2)
>>> b.j = 3
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\home\eric\local\python\cpython\lib\", line 452, in _frozen_setattr
    raise FrozenInstanceError(f'cannot assign to field {name!r}')
dataclasses.FrozenInstanceError: cannot assign to field 'j'

If this can't be addressed before 3.7, maybe it should be an error to declare B as non-frozen and then we can properly fix it in a future release.
Date User Action Args
2018-02-25 22:29:23eric.smithsetrecipients: + eric.smith, rhettinger
2018-02-25 22:29:23eric.smithsetmessageid: <>
2018-02-25 22:29:23eric.smithlinkissue32953 messages
2018-02-25 22:29:23eric.smithcreate