I would like to add some metadata to model fields. This is not necessary for validation or serialisation but might be user for data display or perhaps as a hint when entering data.
For instance one might want to add a unit to a field.

I came up with this:

from pydantic import BaseModel, Field
from typing import Annotated
from dataclasses import dataclass

@dataclass
class MyFieldMetadata:
    unit: str


class MyModel(BaseModel):
    length: Annotated[float, Field(gte=0.0), MyFieldMetadata(unit="meter")]
    duration: Annotated[float, Field(gte=0.0), MyFieldMetadata(unit="seconds")]

and in order to print all fields with the unit postfixed:

m = MyModel(length=10.0, duration=60.0)
for field_name, field_info in m.model_fields.items():
    extra_info = next(
        (m for m in field_info.metadata if isinstance(m, MyFieldMetadata)), None
    )

    print(
        f"{field_name}: {getattr(m, field_name)} {extra_info.unit if extra_info else ''}"
    )

This works, but the question is if this is correct?
And the second question: The way to retrieve MyFieldMetadata from the model seems a convoluted (iterating through meta_data and finding the first instance of MyFieldMetadata). Is there a cleaner or standard way to achieve this?

I’m using pydantic 2.7.1