I wrote the following class:
from typing import Any
from pydantic import BaseModel
class _UnknownFieldExceptionMixin:
model: type[BaseModel]
field: FieldName
def __init__(self, model: type[BaseModel], field: FieldName, *args: Any) -> None:
self.model = model
self.field = field
# super().__init__(model, field, *args)
def __repr__(self) -> str:
return f'{self.__class__.__name__}({self.model.__name__}, {self.field!r})'
def __str__(self) -> str:
return f'Unknown field {self.field!r} for model {self.model.__name__}.'
class UnknownFieldWarning(_UnknownFieldExceptionMixin, Warning):
"""An unknown model field was assigned, and will be ignored."""
pass
class UnknownFieldError(_UnknownFieldExceptionMixin, TypeError):
"""An unknown model field was assigned."""
pass
Note that the call to super().__init__ is commented-out in _UnknownFieldExceptionMixin.__init__.
Nevertheless, when I instantiate UnknownFieldError like so:
class Thing(BaseModel):
x: float
exc = UnknownFieldError(Thing, 'foo')
The exc object has a .args attribute, as if Exception.__init__(*args, **kwargs) had been called:
print(exc.args)
What's going on here? Is this some hard-coded behavior for subclasses of Exception, so that you don't have to deal with super() and *args? Or am I missing something else here?
