How to serialize list of list items to pydantic model

Question

I have response from server:

{
    "date": "2024-02-05 15:34:44",
    "status": True,
    "data": [
        [1, "red"],
        [2, "blue"],
        [3, "yellow"]
    ]
}

And i want to serialize this response to pydantic model, but i don't know how parse list (example [1, "red"]) in pydantic model

class Item(BaseModel): # how convert list from data to this model
    id: int
    color: str
    ...


class Model(BaseModel):
    date: datetime
    status: bool
    data: list[Item]

Answer 1

You can work for example with a model_validator to parse the list into the Item model:

from pydantic import BaseModel, model_validator

data = {
    "date": "2024-02-05 15:34:44",
    "status": True,
    "data": [
        [1, "red"],
        [2, "blue"],
        [3, "yellow"]
    ]
}

class Item(BaseModel):
    id: int
    color: str

    @model_validator(mode="before")
    @classmethod
    def validate(cls, values):
        id, color = values
        return {"id": id, "color": color}
    


class Model(BaseModel):
    date: datetime
    status: bool
    data: list[Item]


print(Model(**data))

Which prints:

date=datetime.datetime(2024, 2, 5, 15, 34, 44) status=True data=[Item(id=1, color='red'), Item(id=2, color='blue'), Item(id=3, color='yellow')]

There are likely other approaches, such as AliasPath, but this one seems the simplest.

I hope this helps!