How to remove dynamically fields from a dataclass?

I want to inherit my dataclass but remove some of its fields. How can I do that in runtime so I don't need to copy all of the members one by one?

Example:

from dataclasses import dataclass

@dataclass
class A:
    a: int
    b: int
    c: int
    d: int

@remove("c", "d")
class B(A):
    pass

Such that A would have a, b, c, d defined and B would only have a and b defined.

Solution

We can remove the particular fields from the __annotations__ dictionary as well as from __dataclass_fields__ and then rebuild our class using dataclasses.make_dataclass:

def remove(*fields):
    def _(cls):
        fields_copy = copy.copy(cls.__dataclass_fields__)
        annotations_copy = copy.deepcopy(cls.__annotations__)
        for field in fields:
            del fields_copy[field]
            del annotations_copy[field]
        d_cls = dataclasses.make_dataclass(cls.__name__, annotations_copy)
        d_cls.__dataclass_fields__ = fields_copy
        return d_cls
    return _

Note that we copy the annotations and the fields in order to not affect A. otherwise it would remove these fields from A as well and any other attempt to inherit A and remove again a field which we already removed would lead to an error. I.e:

from dataclasses import dataclass

@dataclass
class A:
    a: int
    b: int
    c: int
    d: int

@remove("c", "d")
class B(A):
    pass

@remove("b", "c")
class C(A):
    pass

This would give us a KeyError since we already removed "c" and this is no longer exists in A's dictionary.