Validate pydantic fields according to value in other field

Question

I'm trying to validate some field according to other fields, example:

from pydantic import BaseModel, validator
class MyClass(BaseModel):
    type: str
    field1: Optional[str] = None
    field2: Optional[str] = None
    field3: Optional[str] = None

   @validator("type")
   def has_required_fields(cls, v, values):
       required_fields {"v1": ["field1", "field3"], "v2": ["field2"]}
       for required_field in required_fields[c]:
           if not values[required_field]:
               raise Exception

But my issue is that the values dict is empty. How should I access the other fields correctly in this situation?

Answer 1

I believe you need to set “always=True” in the validator if you plan on type being empty when you initialize it. See here:

https://github.com/pydantic/pydantic/issues/691#issuecomment-785101470

Answer 2

Fields are validated in order they are initialized. Dictionary is empty because there is no validated fields as the type is the first field to be validated.

-> Reorder the field initialization or -> Use root validator