Pydantic 1.x (old answer)

The current version of pydantic does not support creating jsonable dict straightforwardly. But you can use the following trick:

Note: This is a suboptimal solution

class Model(BaseModel):
    the_id: UUID = Field(default_factory=uuid4)

print(json.loads(Model().json()))

{'the_id': '4c94e7bc-78fe-48ea-8c3b-83c180437774'}

Or more efficiently by means of orjson

orjson.loads(Model().json())

Pydantic 2

There is the model_dump() method accepting the mode parameter.

mode: Literal['json', 'python'] | str = 'python'

If mode is 'json', the dictionary will only contain JSON serializable types.

If mode is 'python', the dictionary may contain any Python objects.

class Model(BaseModel):
    the_id: UUID = Field(default_factory=uuid4)

print(Model().model_dump(mode='json'))
# {'the_id': '4c94e7bc-78fe-48ea-8c3b-83c180437774'}

Is this enough?

import pydantic
from typing import Any
from pydantic.types import Json

input = {
    "id": 4,
    "data": '{"something":4,"field":"else"}'
}
class MyModel(pydantic.BaseModel):
    id: int
    data: Json[Any] = pydantic.Field(default_factory=dict)  # <<<

model = MyModel.model_validate(input)
print(model)

If all you're trying to do is have a dictionary of BarModel's in another model, this answers your question:

from typing import Dict
from pydantic import BaseModel

class BarModel(BaseModel):
    whatever: float
    foo: str

class FooBarModel(BaseModel):
    dictionaries: Dict[str, BarModel]

m1 = FooBarModel(dictionaries={
    'a': {'whatever': 12.3, 'foo': 'hello'},
    'b': {'whatever': 12.4, 'foo': 'bye'}
}

print(m1.dict())

In Pydantic 2, you can use MyModel.model_validate(my_dict) to generate a model from a dictionary. According to the documentation –

this is very similar to the __init__ method of the model, except it takes a dict rather than keyword arguments.

If you're Pydantic 1, the method is parse_obj instead.