[Python] How to use yaml_file parameter for pydantic settings

Here is my example code:

from pathlib import Path
from pydantic_settings import BaseSettings, SettingsConfigDict

class Settings(BaseSettings):
model_config = SettingsConfigDict(
yaml_file=Path('c.yaml'),
yaml_config_section='blah',
)

port: int


s = Settings()


and my c.yaml stored in the same directory:

blah:
port: 123


When I'm running python file I'm getting message:

pydantic_core._pydantic_core.ValidationError: 1 validation error for Settings
port
Field required [type=missing, input_value={}, input_type=dict]
For further information visit https://errors.pydantic.dev/2.11/v/missing


what means that Pydantic even doesn't trying to read YAML file. I found multiple answers how read yaml and most of it is about how read yaml, convert it to dict and pass the dict as constructor arguments. But I could not find any information why this yaml_file and yaml_config_section exists and what it does?

Is here a simple way to read yaml using these arguments?

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