Declared fields instead of reflection

Project overview and reading path

A service reads a retry limit from a known configuration. Renaming or misspelling a field should be caught during development.

Typical Python

retries = getattr(config, "retrise", 3)

The typo silently selects the fallback. Attribute names passed as strings hide the intended field contract.

Alternative

from dataclasses import dataclass


@dataclass(frozen=True)
class Config:
    retries: int = 3


config = Config()
retries = config.retries

Direct config.retrise is rejected as missing-attribute; the valid access returns 3. The default belongs in the model, where all callers share its policy.

Keep getattr, setattr, hasattr, delattr, and equivalent reflection out of ordinary application logic. Use a protocol for required capabilities and a typed registry for selecting handlers. hasattr does not establish a method signature. Necessary framework adapters and tests may use reflection locally, then return precise types. This is a design policy, not a claim that checkers reject all reflection.