Configuration¶

Configuration classes inherit from patera.BaseConfig, a pydantic-settings model:

import os

from patera import BaseConfig


class Config(BaseConfig):
    BASE_PATH: str = os.path.dirname(__file__)   # required
    APP_NAME: str = "My app"
    SECRET_KEY: str                              # required, e.g. from PATERA_SECRET_KEY

Settings are validated when the application is constructed, so set environment values before constructing the app.

Environment variables¶

Every option can be overridden with an environment variable prefixed with PATERA_. Nested values use __ as separator:

PATERA_DEBUG=false
PATERA_PORT=8080
PATERA_CORS_ALLOW_ORIGINS='["https://app.example.com"]'
PATERA_MAIN_DB__DATABASE_URI=postgresql+asyncpg://user:pass@db/app

Values usually live in .env files; see Running the application for which file each command loads.

Extension and component settings¶

Extension, service and middleware settings are regular fields of your config class, named after the class in UPPER_SNAKE_CASE: MainDb → MAIN_DB, PublicCache → PUBLIC_CACHE. Renaming the class changes the key.

from patera import BaseConfig
from patera.caching import CachingConfig


class Config(BaseConfig):
    BASE_PATH: str = os.path.dirname(__file__)
    PUBLIC_CACHE: CachingConfig = CachingConfig(DURATION=30, MAX_SIZE=500)

A nested dictionary is validated against the component's configuration model; an absent configuration uses the model's defaults if it has no required fields. See Services and dependency injection.

Settings from the environment only¶

The values can live in .env (or the environment) instead of the class. Declare a settings model without a value, and it is built from the variables that are set, with the model's defaults for the rest:

class Config(BaseConfig):
    BASE_PATH: str = os.path.dirname(__file__)
    MAIN_DB: SqlDatabaseConfig    # PATERA_MAIN_DB__DATABASE_URI must be set
    DESKTOP: DesktopConfig        # every field has a default; PATERA_DESKTOP__WIDTH=1200 changes one

A required field that no variable sets stops the application at startup with its name (MAIN_DB.DATABASE_URI: Field required). A model declared with a value in the class (MAIN_DB: SqlDatabaseConfig = SqlDatabaseConfig(...)) keeps that value as its default, and variables change single fields of it.

Reading configuration¶

• app.configs.NAME: typed attribute access.
• app.get_conf("NAME", default): supports dotted paths into nested models and dictionaries, for example app.get_conf("MAIN_DB.DATABASE_URI") or app.get_conf("DEFAULT_LOGGER.LEVEL").
• The ConfigVar descriptor in controllers and services:

from patera.injectable import ConfigVar


@path("/greetings")
class GreetingApi(Controller["App"]):
    app_name: str = ConfigVar("APP_NAME")
    label: str = ConfigVar("GREETING_LABEL", "Greetings")   # with default

ConfigVar reads settings through the application lookup path; it does not declare a required Pydantic field.

Built-in options¶

The most important built-in options are BASE_PATH, APP_NAME, VERSION, DEBUG, HOST, PORT, URL_PREFIX, MAX_CONTENT_LENGTH and the CORS_*, OPEN_API*, TEMPLATES_* and STATIC_* groups. The complete table with defaults is in the configuration reference.