Sources

A source loads configuration from one origin and returns a plain dict. ConfigLoader merges multiple sources in order.

DictSource

Wraps an in-memory dict. Useful for defaults and test fixtures.

from molcfg import DictSource

src = DictSource({"db": {"host": "localhost", "port": 5432}}, name="defaults")
data = src.load()

JsonFileSource

Reads a JSON file from disk.

from molcfg import JsonFileSource

src = JsonFileSource("config.json", name="file")

TomlFileSource

Reads a TOML file from disk.

from molcfg import TomlFileSource

src = TomlFileSource("config.toml", name="file")

EnvSource

Reads environment variables and maps them into nested keys by splitting on _.

from molcfg import EnvSource

src = EnvSource(
    prefix="APP",
    environ={
        "APP_DB_HOST": "prod-db",
        "APP_DB_PORT": "5432",
        "APP_DEBUG": "true",
    },
)

assert src.load() == {
    "db": {"host": "prod-db", "port": 5432},
    "debug": True,
}

prefix is stripped and not included in the output key. Keys are lowercased. Pass environ= to inject a custom env dict (useful in tests); omit it to read os.environ.

CliSource

Parses a list of --key=value or --key value arguments.

from molcfg import CliSource

src = CliSource(["--db.host=localhost", "--db.port", "5432", "--debug=true"])
assert src.load() == {"db": {"host": "localhost", "port": 5432}, "debug": True}

Dotted keys map directly to nested dicts.

Coercion

EnvSource and CliSource coerce string values by default:

Input	Result
"true" / "false"	bool
"5432"	int
"3.14"	float
"null" / "none"	None
'["a","b"]'	list
'{"x":1}'	dict

Pass coerce=False to keep raw strings.

Naming sources

All sources accept a name argument recorded in metadata:

DictSource({"x": 1}, name="defaults")
EnvSource(prefix="APP", name="env")

Use stable, descriptive names. They appear in Config.meta() history.