TypeError: __init__() got an unexpected keyword argument 'is_class' in pydantic V2

[atompie]

Hello

Today I wanted to start my journey with pydantic V2 and prepare myself for my project migration. I installed a fresh venv and pip install pydantic==2.0b3. I am using python 3.8.

a Simple example:

from datetime import datetime
from typing import List, Optional
from pydantic import BaseModel

class User(BaseModel):
    id: int
    name = 'John Doe'
    signup_ts: Optional[datetime] = None
    friends: List[int] = []

external_data = {'id': '123', 'signup_ts': '2017-06-01 12:22', 'friends': [1, '2', b'3']}
user = User(**external_data)
print(user)
#> User id=123 name='John Doe' signup_ts=datetime.datetime(2017, 6, 1, 12, 22) friends=[1, 2, 3]
print(user.id)
#> 123

gives me this error.

Traceback (most recent call last):
  File "/home/risto/PycharmProject/pythonProject/pydantic2/main.py", line 3, in <module>
    from pydantic import BaseModel
  File "/home/risto/PycharmProject/pythonProject/pydantic2/venv/lib/python3.9/site-packages/pydantic/__init__.py", line 22, in <module>
    from .deprecated.tools import *
  File "/home/risto/PycharmProject/pythonProject/pydantic2/venv/lib/python3.9/site-packages/pydantic/deprecated/tools.py", line 10, in <module>
    from ..type_adapter import TypeAdapter
  File "/home/risto/PycharmProject/pythonProject/pydantic2/venv/lib/python3.9/site-packages/pydantic/type_adapter.py", line 12, in <module>
    from pydantic.main import BaseModel
  File "/home/risto/PycharmProject/pythonProject/pydantic2/venv/lib/python3.9/site-packages/pydantic/main.py", line 1121, in <module>
    class RootModel(BaseModel, typing.Generic[RootModelRootType]):
  File "/home/risto/PycharmProject/pythonProject/pydantic2/venv/lib/python3.9/site-packages/pydantic/_internal/_model_construction.py", line 175, in __new__
    set_model_fields(cls, bases, config_wrapper, types_namespace)
  File "/home/risto/PycharmProject/pythonProject/pydantic2/venv/lib/python3.9/site-packages/pydantic/_internal/_model_construction.py", line 347, in set_model_fields
    fields, class_vars = collect_model_fields(cls, bases, config_wrapper, types_namespace, typevars_map=typevars_map)
  File "/home/risto/PycharmProject/pythonProject/pydantic2/venv/lib/python3.9/site-packages/pydantic/_internal/_fields.py", line 93, in collect_model_fields
    type_hints = get_cls_type_hints_lenient(cls, types_namespace)
  File "/home/risto/PycharmProject/pythonProject/pydantic2/venv/lib/python3.9/site-packages/pydantic/_internal/_typing_extra.py", line 221, in get_cls_type_hints_lenient
    hints[name] = eval_type_lenient(value, globalns, localns)
  File "/home/risto/PycharmProject/pythonProject/pydantic2/venv/lib/python3.9/site-packages/pydantic/_internal/_typing_extra.py", line 232, in eval_type_lenient
    value = _make_forward_ref(value, is_argument=False, is_class=True)
TypeError: __init__() got an unexpected keyword argument 'is_class'

Process finished with exit code 1

What am I doing wrong. Where can I discuss this issue.

[Kludex]

• I think we had a regression on Improve test coverage of pydantic._internal._typing_extra #5978.

You are not doing anything wrong. Thanks for reporting it. 👍

[Kludex]

I can't reproduce your issue. What is the exact Python version that you are running? On 3.8.14 it runs fine.

[Kludex]

It says you are running on 3.9 on your logs. 😅

EDIT: Which I can't reproduce as well.
EDIT2: The only thing missing is the str type hint on the name field.

[atompie]

@Kludex Sorry my mistake, my version is Python 3.9.5 on Ubuntu.

[Kludex]

Yeah... I can reproduce on 3.9.5, but I can't on 3.9.16. Thanks.

[Kludex]

It looks like the backport that solved that was merged in September 2021 for 3.9: python/cpython#28561 (comment)

Since the next released version was 3.9.8...

We need to change the conditional here:

pydantic/pydantic/_internal/_typing_extra.py

Line 254 in ba8ee95

if sys.version_info < (3, 9):

to:

if sys.version_info < (3, 9, 8):

[atompie]

Yeah... I can reproduce on 3.9.5, but I can't on 3.9.16. Thanks.

Perfect till then I will upgrade to 3.9.16

[Kludex]

Ah... If you can do that, then great. 😅

Thanks.

[ozzzzz]

Just want to mention that I have the same error on version 3.10.0. Issue solved when I updated to the version 3.10.11.

[BluLupo]

With the 3.10.0 python version it doesn't work I solved the problem by updating to the 3.11.3 version

[xmak]

I get the same error when I try from pydantic import RootModel. Python 3.10.0