Pydantic

pydantic_verbosity.py

from pydantic import BaseModel, ValidationError
from typing import Union


class A(BaseModel):
    a: Union["A", "B"]


class B(BaseModel):
    a: Union["A", "B"]


def generate_data(n):
    out = {"a": "nope"}

    for i in range(0, n):
        out = {"a": out}

    return out


if __name__ == "__main__":
    A.update_forward_refs()
    B.update_forward_refs()

    data = generate_data(10)

    try:
        a = A(**data)
    except ValidationError as e:
        print(e.json())