pydantic-settings-file-envar

Support for loading pydantic-settings from files, using the _FILE environment variable suffix pattern commonly used in container images, especially official Docker images.

If you have a setting called foo, by default pydantic-settings will load it from an environment variable FOO. With pydantic-settings-file-envar, if an environment variable FOO_FILE=/a/b/foo is set, the secret's value will be loaded from the file at /a/b/foo.

Note that pydantic-settings has built-in support for loading secrets from files, so that may be all you need. It's different from the _FILE envar pattern in that it expects a specific directory to be specified, which contains appropriately-named secret files.

Install

$ pip install pydantic-settings-file-envar

Usage

To use _FILE envar settings, override the settings_customise_sources() class method of your settings class to include the FileSuffixEnvSettingsSource this package provides:

from pydantic_settings_file_envar import FileSuffixEnvSettingsSource

# ...

class ExampleSettings(BaseSettings):
    threshold: int
    launch_code: str

    @classmethod
    def settings_customise_sources(
        cls,
        settings_cls: Type[BaseSettings],
        init_settings: PydanticBaseSettingsSource,
        env_settings: PydanticBaseSettingsSource,
        dotenv_settings: PydanticBaseSettingsSource,
        file_secret_settings: PydanticBaseSettingsSource,
    ) -> Tuple[PydanticBaseSettingsSource, ...]:
        # Adding FileSuffixEnvSettingsSource enables _FILE envars
        return (init_settings, env_settings, FileSuffixEnvSettingsSource(settings_cls))

If you place it after the default env_settings source, _FILE environment variable will only be used if a regular environment variable is not set. The pydantic-settings docs have more details on configuring settings sources.

Example program & Docker image

The ./example dir contains an example command-line program that loads settings using regular or _FILE envars.

Try it like this:

$ cd example
$ poetry install --with local
$ poetry shell
$ echo -n secret-from-file > /tmp/secret
$ THRESHOLD=9000 LAUNCH_CODE_FILE=/tmp/secret file-envar-example
Loaded settings: threshold=9000 launch_code='secret-from-file'

Or the Docker image:

$ # build the example image
$ docker buildx bake example
[+] Building 5.2s (12/12) FINISHED                                                                         ...
 => => naming to docker.io/library/file-envar-example

$ echo -n secret-from-file > /tmp/secret
$ docker container run --rm -v /tmp:/secrets -e THRESHOLD=9000 -e LAUNCH_CODE_FILE=/secrets/secret file-envar-example
Loaded settings: threshold=9000 launch_code='secret-from-file'

Developing

See docs/dev.md.