How to modify serialization of models recursively in pydantic V2

Question

in V1 I was able to recursively add information to the BaseModel.dict method. Is something similar possible in V2?

In V1 this was possible:

from typing import Optional

from pydantic.v1 import BaseModel


class BaseModel2(BaseModel):
    def dict(self, **kwargs):
        _dict = super().dict(**kwargs)
        _dict["__name__"] = self.__class__.__name__
        return _dict


class Foo(BaseModel2):
    whatever: int


class Bar(BaseModel2):
    whenever: Optional[float] = 1.1
    foo: Foo


m = Bar(whenever=3.14, foo=Foo(whatever=123))
print(m.dict())

As a result, the dictionary would contain a __name__ for both models, as dict was called recursively.

Tom McLean · Accepted Answer · 2024-12-10 11:21:03Z

2

You could do this:

from typing import Optional

from pydantic import BaseModel, computed_field


class BaseModel2(BaseModel):

    @computed_field(alias="__name__")
    @property
    def name(self) -> str:
        return self.__class__.__name__


class Foo(BaseModel2):
    whatever: int


class Bar(BaseModel2):
    whenever: Optional[float] = 1.1
    foo: Foo


m = Bar(whenever=3.14, foo=Foo(whatever=123))
print(m.model_dump(by_alias=True))

answered Dec 10, 2024 at 11:21

Tom McLean

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2 Comments

GermanExpress Dec 10, 2024 at 15:54

This is a great suggestion, let me play a bit with it, and then I think I will accept this as answer!

GermanExpress Dec 10, 2024 at 16:15

Do you think there is an alternative way that does not define a new field that would get serialized all the time. What I was able to achieve with the V1 solution (not shown) is to define a contextmanager, that would only call the additional logic when requested, so that normal serialization would still be unaffected

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