Validation based on previous attribute

[mfrata]

Hi. 👋🏾

Is there a way to validate an attribute based on a previous one?

E.g:

from pydantic import BaseModel, validator
from typing import Optional

class Customer(BaseModel):
    ...
    wantsJuice: bool
    typeOfJuice: Optional[str] = None
    @validator("typeOfJuice")
    def check_type_of_juice_is_defined_if_wants_juice(cls, val):
        # if wantsJuice is True, typeOfJuice must be defined
        # else, ignore value of typeOfJuice

I've tried to access the cls and check if wantsJuice was defined. But couldn't find its reference there.
Also, I've tried to pass both of them(@validator("wantsJuice","typeOfJuice")) as I saw here but check_type_of_juice_is_defined_if_wants_juice is called twice for each one, instead of once for both of them.

Thanks for the awesome lib!! 🚀

[PrettyWood]

Hi @mfrata and welcome!

You can have a look at the doc, which contains an example with values that contain the values already checked. Furthermore you probably want to use always=True to check the default value (in your case None).
Putting everything together you get

class Customer(BaseModel):
    wantsJuice: bool
    typeOfJuice: Optional[str] = None

    @validator("typeOfJuice", always=True)
    def check_type_of_juice_is_defined_if_wants_juice(cls, val, values):
        if values.get('wantsJuice') and val is None:
            raise ValueError('typeOfJuice can not be None')
        return val

Hope it helps 😃

[samuelcolvin]

First discussion 👌

[mfrata]

Hi @PrettyWood and @samuelcolvin. It worked like a charm! Thanks a lot. You guys rock!!