The Init Function

If config.py contains an init function, it is called during LLMRails initialization. Use it to set up shared resources and register action parameters.

Important

The init function must be synchronous (def init, not async def init). The framework calls it without await, so an async function would silently do nothing.

Any top-level code in config.py runs at import time, before init() is called. This can be used for provider registration that does not require the LLMRails instance.

Basic Usage

from nemoguardrails import LLMRails

def init(app: LLMRails):
    # Initialize database connection
    db = DatabaseConnection()

    # Register as action parameter (available to all actions)
    app.register_action_param("db", db)

Registering Action Parameters

Action parameters registered in config.py are automatically injected into actions that declare them. The runtime matches parameters by name, i.e., the parameter name in the action must match the name used during registration.

config.py:

import os

from nemoguardrails import LLMRails

def init(app: LLMRails):
    # Initialize shared resources
    db = DatabaseConnection(host="localhost", port=5432)
    api_client = ExternalAPIClient(api_key=os.environ.get("API_KEY"))

    # Register as action parameters
    app.register_action_param("db", db)
    app.register_action_param("api_client", api_client)

actions.py:

from nemoguardrails.actions import action

@action()
async def fetch_user_data(user_id: str, db=None):
    """The 'db' parameter is injected from config.py."""
    return await db.get_user(user_id)

@action()
async def call_external_service(query: str, api_client=None):
    """The 'api_client' parameter is injected from config.py."""
    return await api_client.search(query)

Built-in Action Parameters

In addition to parameters you register, the runtime automatically injects these built-in parameters into any action that declares them:

Parameter	Type	Description
config	RailsConfig	The full rails configuration object
context	dict	The current conversation context
events	list	The event history
llm	LLM instance	The main LLM (auto-registered during initialization)
llm_task_manager	LLMTaskManager	Manages LLM task execution

See Custom Data for details on accessing config.custom_data inside actions.

Accessing the Configuration

The app parameter provides access to the full configuration:

def init(app: LLMRails):
    # Access the RailsConfig object
    config = app.config

    # Access custom data from config.yml
    custom_settings = config.custom_data

    # Access model configurations
    models = config.models

Example: Database Connection

import os
import psycopg2
from nemoguardrails import LLMRails

def init(app: LLMRails):
    # Create connection pool
    conn = psycopg2.connect(
        host=os.environ.get("DB_HOST", "localhost"),
        database=os.environ.get("DB_NAME", "mydb"),
        user=os.environ.get("DB_USER", "user"),
        password=os.environ.get("DB_PASSWORD"),
    )

    app.register_action_param("db_conn", conn)

Example: API Client Initialization

import os
import httpx
from nemoguardrails import LLMRails

def init(app: LLMRails):
    # Get API key from custom_data in config.yml
    api_key = os.environ.get("API_KEY") or app.config.custom_data.get("api_key")

    # Create HTTP client with authentication
    client = httpx.AsyncClient(
        base_url="https://api.example.com",
        headers={"Authorization": f"Bearer {api_key}"}
    )

    app.register_action_param("http_client", client)