ymlmaster

ymlmaster is a configuration loading utility for Python 3.12+. It provides a unified interface for loading deeply structured YAML configuration files (optionally combined with .env overrides) into statically typed Python classes using either dataclass or pydantic.

Features

• Schema generation from YAML into @dataclass or Pydantic models
• Nested structures supported automatically
• Preserves docstrings, base class inheritance, and field customizations during regeneration
• .env merging with environment variable fallback (and alias remapping support)
• URL field generation (*_url) based on structured service info (host, port, etc.)
• Smart handling of comma-separated env vars to generate multiple URLs
• Profile support (e.g., dev, release)
• CLI generator for schema models

Installation

pip install ymlmaster
# or
poetry add ymlmaster

Schema Example

Example YAML:

dev:
  postgresql:
    host: null
    user: null
    password: null
    port: null
    db: null

  redis:
    host: "127.0.0.1"
    port: null

  application:
    token: null
    admin_id: null

Example .env:

POSTGRESQL__USER=user_pg
POSTGRESQL__PASSWORD=password_pg
POSTGRESQL__PORT=5432,2345
POSTGRESQL__HOST=localhost,198.168.0.101
APPLICATION__TOKEN=123456:geJhasfjJD2f
APPLICATION__ADMIN_ID=12345

Model Generation CLI

poetry run generate-schema \
  --settings settings.yml \
  --output settings_model.py \
  --type dataclass \
  --profile dev \
  --urls postgresql redis

This will generate (preserving comments, docstrings, fields, and base classes):

@dataclass
class Postgresql:
    host: Optional[str] = None
    user: Optional[str] = None
    ...

@dataclass
class Settings:
    postgresql: Postgresql = None
    postgresql_url: Optional[str | list[str]] = None
    redis_url: Optional[str | list[str]] = None

Same works with:

class Postgresql(BaseModel): ...
class Settings(BaseModel): ...

How It Works

Block-based configuration:

• YAML supports separate config blocks like dev, release, stage, etc.
• --profile dev chooses which one to load
• Default is dev

You can automate environment selection via:

use_release = not Path(".developer").exists()
loader = SettingsLoader(..., use_release=use_release)

This assumes:

• .developer exists on local machines (and ignored via .gitignore)
• When not found → production (auto picks release)

SettingsLoader Parameters

Smart URL Generation

With .env like:

POSTGRESQL__HOST=localhost,10.0.0.2
POSTGRESQL__USER=user1,user2
POSTGRESQL__PORT=5432,5433

and:

url_templates = {
  "postgresql": "postgresql+asyncpg"
}

Settings.postgresql_url becomes:

[
  "postgresql+asyncpg://user1:...@localhost:5432/dbname",
  "postgresql+asyncpg://user2:...@10.0.0.2:5433/dbname"
]

You can mix single and multiple values — host count defines length of list.

Example Usage

from ymlmaster import SettingsLoader
from settings_model_pydantic import Settings

ALIASES_MAP = {
    "PGUSER": "POSTGRESQL__USER",
    "PGPASSWORD": "POSTGRESQL__PASSWORD",
    "PGPORT": "POSTGRESQL__PORT",
    "PGDB": "POSTGRESQL__DB",
}

loader = SettingsLoader(
    settings_path=Path("settings.yml"),
    env_path=Path(".env"),
    model_class=Settings,
    use_release=False,
    profile=None,
    url_templates={
        "postgresql": "postgresql+asyncpg",
        "redis": "redis"
    },
    env_alias_map=ALIASES_MAP,
    dev_block="dev",             # you can change to "development"
    release_block="release",     # you can change to "production"
)

cfg = loader.load()
print(cfg.redis_url)
print(cfg.postgresql_url)

Docker Compatibility

• Values from .env are injected only if the YAML value is null
• Nested overrides use __ as separator:
  • For application.token → APPLICATION__TOKEN
  • For redis.port → REDIS__PORT

If the key ends with port and is an integer, a default IP of 127.0.0.1: is prepended unless already present.

This separation helps to use sensitive data in Dockerfile/DockerCompose and in your project at once Example docker-compose.yml:

services:
  q3s2j0pj0fuj:
    image: "postgres:17"
    container_name: "q3s2j0pj0fuj"
    environment:
      POSTGRES_DB: ${POSTGRESQL__DB}
      POSTGRES_USER: ${POSTGRESQL__USER}
      POSTGRES_PASSWORD: ${POSTGRESQL__PASSWORD}
    ports:
      - "${POSTGRESQL__PORT}:5432"
    logging:
      driver: "json-file"
      options:
        max-size: "10m"
        max-file: "3"
    networks:
      - Network
    restart: always

MIT LICENSE