OmegaConf

from omegaconf import OmegaConf
import os

# Create a config from a dictionary
conf = OmegaConf.create({
    "database": {
        "host": "localhost",
        "port": 5432,
        "user": "${oc.env:DB_USER, default_user}"
    },
    "server": {
        "port": "${database.port}"
    }
})

# Access config values
print(f"Database host: {conf.database.host}")
print(f"Database user: {conf.database.user}") # Resolves from env var or default
print(f"Server port: {conf.server.port}")

# You can also load from YAML strings or files
yaml_string = """
app:
  name: my_app
  version: 1.0
"""
app_conf = OmegaConf.create(yaml_string)
print(f"App name: {app_conf.app.name}")

# Overriding values
conf.database.host = "remote_db"
print(f"Updated database host: {conf.database.host}")

# Example of structured config with dataclasses (requires Python 3.7+ or dataclasses backport for 3.6)
from dataclasses import dataclass

@dataclass
class DatabaseConfig:
    host: str = "127.0.0.1"
    port: int = 5432

@dataclass
class Config:
    db: DatabaseConfig = DatabaseConfig()
    debug: bool = False

structured_conf = OmegaConf.structured(Config)
print(f"Structured config DB host: {structured_conf.db.host}")

# Set an environment variable for testing
os.environ['DB_USER'] = 'my_secret_user'
resolved_user_conf = OmegaConf.create({"db_user": "${oc.env:DB_USER}"})
print(f"Resolved DB user from env: {resolved_user_conf.db_user}")
del os.environ['DB_USER'] # Clean up