Why does Pydantic hide the exception-raising line?

Question

I'm using Pydantic and there's something that makes me curious, exceptions raised from Pydantic hides the line raising the exception.

For example with this code:

from typing import Any

from pydantic import BaseModel
from pydantic.error_wrappers import ErrorWrapper, ValidationError
from pydantic.utils import ROOT_KEY


class MyModel(BaseModel):
    def __init__(self, **data: Any) -> None:
        exc = TypeError(f"My TypeError")
        raise ValidationError([ErrorWrapper(exc, loc=ROOT_KEY)], self.__class__)
        super().__init__(**data)


class Foo(MyModel):
    a: int


class Bar(BaseModel):
    a: int

The exception raised from my custom model will print the line raising the exception:

Foo(a=42)
# Traceback (most recent call last):
#   File "D:\_exc.py", line 23, in <module>
#     Foo(a=42)
#   File "D:\_exc.py", line 11, in __init__
#     raise ValidationError([ErrorWrapper(exc, loc=ROOT_KEY)], self.__class__)
# pydantic.error_wrappers.ValidationError: 1 validation error for Foo
# __root__
#   My TypeError (type=type_error)

But exceptions raised from Pydantic's default BaseModel will hide the line raising the exception:

Bar(a="foo")
# Traceback (most recent call last):
#   File "D:\_exc.py", line 25, in <module>
#     Bar(a="foo")
#   File "pydantic\main.py", line 331, in pydantic.main.BaseModel.__init__
# pydantic.error_wrappers.ValidationError: 1 validation error for Bar
# a
#   value is not a valid integer (type=type_error.integer)

Bar.parse_obj(42)
#   File "D:\_exc.py", line 42, in <module>
#     Bar.parse_obj(42)
#   File "pydantic\main.py", line 510, in pydantic.main.BaseModel.parse_obj
# pydantic.error_wrappers.ValidationError: 1 validation error for Bar
# __root__
#   Bar expected dict not int (type=type_error)

Is this some kind of default behavior for external Python libraries? I tried to look through Pydantic's codebase, but it doesn't seem to do anything special when raising the exception.

Why does Pydantic hide the exception-raising line?

0 Answers0