conf-loaders 0.5.0

configuration loading utils

conf-loaders

Configuration loading utilities for Python projects. Load settings from YAML with environment variable substitution, relative path resolution, encrypted passwords, and advanced merge operations.

pip install conf-loaders

What it does

conf-loaders solves the problem of keeping default settings in Python code while allowing local overrides via YAML files. It provides:

• YAML settings loading with automatic environment variable substitution (${VAR} or ${VAR:-default})
• Relative path resolution — relative paths in YAML are resolved to absolute paths automatically
• Update operations — extend lists, append items, update dicts without replacing the whole structure
• Encrypted passwords — load AES/RSA encrypted secrets from separate YAML files
• Environment variable parsing — parse prefixed environment variables into nested dict structures

Quick start

Basic usage in Django/Flask settings.py

# settings.py — default values
DEBUG = False
ALLOWED_HOSTS = ["localhost"]
DATABASES = {
    "default": {"ENGINE": "django.db.backends.sqlite3"}
}

# config.yaml — local overrides
DEBUG: true
ALLOWED_HOSTS@extend:
  - "my-domain.com"
DATABASES@update:
  default:
    NAME: "/path/to/db.sqlite3"

# At the end of settings.py
from conf_loaders.utils.settings_load import load_settings_from_yaml
load_settings_from_yaml("config.yaml", object_to_update=locals())

After loading, locals() contains merged values from both sources.

Features

Environment variable substitution

YAML files are pre-processed with varsubst before parsing:

DB_HOST: "${DB_HOST:-localhost}"
DB_PORT: "${DB_PORT:-5432}"

Relative path resolution

String values that look like relative paths are resolved to absolute paths using base_dir:

# Relative to the directory passed as base_dir
LOG_PATH: "../../data/logs/app.log"
MODEL_DIR: "./models"

To disable resolution for a specific value, prefix it with !:

# Will remain "./relative/path" without resolution
PATTERN: "!./relative/path"

Path resolution is recursive — works inside nested dicts and lists.

U can disable all these operations by setting base_dir=....

Update operations

By default, a YAML key replaces the entire Python value. Use @operation suffixes to merge instead:

@extend — extend a list

ALLOWED_HOSTS@extend:
  - "api.example.com"
  - "app.example.com"

@append — append a single item

ALLOWED_HOSTS@append: "admin.example.com"

@update — update a dict (merge keys)

DATABASES@update:
  default:
    HOST: "postgres.internal"

@bind — replace contents, keep object reference

Useful when other modules hold references to the list/dict:

# Clears SCRIPT_ROOTS and fills with new values,
# but the list object in memory stays the same
SCRIPT_ROOTS@bind:
  - scripts/common/
  - scripts/custom/

@setdefault — set only if not defined

DEBUG@setdefault: false

If DEBUG is already defined in settings.py, the YAML value is ignored.

Full operation reference

Operation	Effect	Requires existing var
(no suffix)	Replace entirely	No
@setdefault	Set only if undefined	No
@bind	Clear + refill, keep object reference	No
@append	Append one item to list	Yes
@try-append	Append one item, create list if missing	No
@extend	Extend list with multiple items	Yes
@try-extend	Extend list, create if missing	No
@update	Merge dict keys	Yes
@try-update	Merge dict keys, create dict if missing	No

Nested key access

Operations support dot-notation for nested structures:

# Sets DATABASES["default"]["PORT"] = 5433
DATABASES.default.PORT: 5433

# Appends to nested list
DATABASES.default.OPTIONS@append: "sslmode=require"

Encrypted passwords

Store sensitive values in a separate encrypted file:

from conf_loaders.utils.settings_load import load_passwords_from_yaml

load_passwords_from_yaml(
    passwords_file="secrets.yaml",
    secret_key_file=".secret.key",
    object_to_update=locals(),
)

# secrets.yaml
DB_PASSWORD: "AES$salt$ciphertext"
API_KEY: "AES$salt$ciphertext"

Supported algorithms: AES, RSA.

Environment variable parsing

Load prefixed environment variables into settings:

from conf_loaders.utils.settings_load import load_vars_from_env

load_vars_from_env(
    object_to_update=locals(),
    prefix="MYAPP_",      # Only vars starting with MYAPP_
    secret_key_file=".secret.key",  # Auto-decrypt encrypted values
)

With MYAPP_DB_HOST=localhost and MYAPP_DB_PORT=5432 in environment:

# Results in:
DB_HOST = "localhost"
DB_PORT = "5432"

Double underscores create nested dicts: MYAPP_CACHE__REDIS__HOST=localhost → CACHE["REDIS"]["HOST"] = "localhost".

API reference

load_settings_from_yaml

load_settings_from_yaml(
    path: str | Path,
    object_to_update: MutableMapping[str, Any],
    base_dir: str | Path | None = None,
    show_update_errors: bool = True,
)

• path — path to YAML file
• object_to_update — dict-like object to update, usually locals()
• base_dir — directory for resolving relative paths; None disables resolution
• show_update_errors — whether to print values in error messages

load_passwords_from_yaml

load_passwords_from_yaml(
    passwords_file: str | Path,
    secret_key_file: str | Path,
    object_to_update: MutableMapping[str, Any],
    password_sep: str = "$",
) -> Dict[str, Dict[str, str]]

Returns a dict of successfully decrypted variables with their algorithms and keys.

load_vars_from_env

load_vars_from_env(
    object_to_update: MutableMapping[str, Any],
    secret_key_file: str | Path | None = None,
    password_sep: str = "$",
    prefix: str = "TRANSLATE_",
)

save_settings_debug

save_settings_debug(settings: Mapping[str, Any])

If settings contains SAVE_SETTINGS_DEBUG key with a file path, dumps all settings to that file as JSON (for debugging).

File utilities

conf_loaders.utils.docrender_utils.files provides helpers for common file operations:

• read_yaml(path) / write_yaml(path, data) — YAML I/O
• read_json(path) / write_json(path, data) — JSON I/O
• read_text(path) / write_text(path, text) — Text I/O
• mkdir(path) / mkdir_of_file(path) / mkparents(path) — Directory creation
• copy_file(src, dst) / move_file(src, dst) — File operations
• touch(path) / rmdir(path) — Basic file ops

Changelog

0.4.0

• Relative path resolution is now recursive — works inside nested dicts and lists, not just top-level values
• Values starting with ! are excluded from path resolution

Earlier versions

• Initial release with YAML loading, varsubst, update operations, encrypted passwords, and env var parsing