Can not use ValidataionError __init__ method

[so1n]

Initial Checks

• I confirm that I'm using Pydantic V2

Description

Can not use ValidataionError init method

Example Code

>>> from pydantic import ValidationError
>>> ValidationError([])
Traceback (most recent call last):
  File "/usr/lib/python3.7/code.py", line 90, in runcode
    exec(code, self.locals)
  File "<input>", line 1, in <module>
TypeError: No constructor defined
>>> from pydantic import ValidationError
>>>ValidationError(errors=[])
Traceback (most recent call last):
  File "/usr/lib/python3.7/code.py", line 90, in runcode
    exec(code, self.locals)
  File "<input>", line 1, in <module>
TypeError: No constructor defined
>>> from pydantic import ValidationError
>>> dir(ValidationError)
['__cause__', '__class__', '__context__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__setstate__', '__sizeof__', '__str__', '__subclasshook__', '__suppress_context__', '__traceback__', 'args', 'error_count', 'errors', 'from_exception_data', 'json', 'title', 'with_traceback']

Python, Pydantic & OS Version

pydantic version: 2.0.3
        pydantic-core version: 2.3.0 release build profile
                 install path: .venv/lib/python3.7/site-packages/pydantic
               python version: 3.7.3 (default, Nov  1 2022, 10:27:39)  [GCC 8.3.0]
                     platform: Linux-5.15.77-amd64-desktop-x86_64-with-Deepin-20.9-apricot
     optional deps. installed: ['typing-extensions']

Selected Assignee: @hramezani

[adriangb]

There is no __init__. You’ll have to use from_err_details

[so1n]

Thanks for your reply, but I can't find the from_err_details method. Is it the from_exception_data method?

>>> from pydantic import ValidationError
>>> dir(ValidationError)
['__cause__', '__class__', '__context__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__setstate__', '__sizeof__', '__str__', '__subclasshook__', '__suppress_context__', '__traceback__', 'args', 'error_count', 'errors', 'from_exception_data', 'json', 'title', 'with_traceback']

[adriangb]

Yes sorry, apologies for the misnomer.

[dineshbvadhia]

@adriangb @so1n Hello. I get the same error (with V2 but not with V1) and don't understand what the fix is. Here is a sample code snippet:

from fastapi.exceptions import HTTPException, RequestValidationError
from pydantic import ValidationError

try:
    this = something('odd')
except:
    raise RequestValidationError(errors=[ValidationError(ValueError('Invalid oddness'), 'odd')])

TypeError: No constructor defined

What is the solution?

[adriangb]

Use ValidationError.from_err_details.

[dineshbvadhia]

@adriangb I think you meant to say use ValidationError.from_exception_data which gives a TypeError :(

from fastapi.exceptions import HTTPException, RequestValidationError
from pydantic import ValidationError

try:
    this = something('odd')
except:
    raise RequestValidationError(errors=[ValidationError.from_exception_data(ValueError('Invalid oddness'), 'odd')])

TypeError: argument 'line_errors': 'str' object cannot be converted to 'PyList'

[Kludex]

@dineshbvadhia Eh... I recommend setting up any kind of type checker on your setup.

The API documentation may help you: https://docs.pydantic.dev/latest/api/pydantic_core/#pydantic_core._pydantic_core.ValidationError.from_exception_data

[somnam]

I'm facing this error (TypeError: No constructor defined) when retrieving exception from a Celery task. The error is raised when a pickled ValidataionError is being unpickled. I've found this issue in pydantic-core repo:
pydantic/pydantic-core#959
Is it possible to have __init__ method on ValidataionError?