[Python] Remove exeption type in pydantic field validator error message

I am using fastapi with pydantic for a school project. Let's say I have this little code:

from pydantic import BaseModel, Field, model_validator

class Product(BaseModel):
price: float = Field(ge=0, description="Price must be non-negative")

@model_validator(mode="before")
def validate_price(cls, values):
if values.get("price") < 0:
raise ValueError("Price cannot be negative")
return values

try:
product = Product(price=-100)
except Exception as e:
print(e)


The console log the message:

1 validation error for Product
Value error, Price cannot be negative [type=value_error, input_value={'price': -100}, input_type=dict]
For further information visit https://errors.pydantic.dev/2.11/v/value_error


My question is, how to remove the text Value error, in the full string Value error, Price cannot be negative with a nice and clean way?

The only workaround I found is the next one, the exeption handler from fastapi. I provide my full handler, you just need to look for lines who define error_type and error_message:

@app.exception_handler(RequestValidationError)
async def validation_exception_handler(request, exc):
errors_dict = {}
for error in exc.errors():
error_type = error.get("type").capitalize().replace("_", " ")
error_message = error.get("msg").removeprefix(f"{error_type}, ")
location = error.get("loc")[-1]
errors_dict[location] = {"type": error.get("type"), "message": error_message}
return JSONResponse(
status_code=400,
content={"message": "Erreur lors de la validation", "errors": error_dict},
)


I am expecting to alter the message at the pydantic level, the lowest rather than at the fast api level.

Thanks for advance

Continue reading...