Python YAML Settings to ENV Variables

Python web frameworks commonly use YAML for configuration during development and environment variables for production. Converting between them involves understanding framework-specific conventions and Python's type coercion patterns.

Django settings.yml (loaded via PyYAML):

django:
  secret_key: "django-insecure-dev-key-change-me"
  debug: true
  allowed_hosts:
    - localhost
    - 127.0.0.1
    - ".example.com"
database:
  engine: django.db.backends.postgresql
  name: myproject
  user: postgres
  password: localpass
  host: localhost
  port: 5432
cache:
  backend: django.core.cache.backends.redis.RedisCache
  location: "redis://localhost:6379/1"
email:
  backend: django.core.mail.backends.smtp.EmailBackend
  host: smtp.gmail.com
  port: 587
  use_tls: true
  host_user: "user@example.com"
  host_password: "app-password"

Equivalent .env file (for django-environ):

# Django core
DJANGO_SECRET_KEY=django-insecure-dev-key-change-me
DJANGO_DEBUG=True
DJANGO_ALLOWED_HOSTS=localhost,127.0.0.1,.example.com

# Database (django-environ uses a DATABASE_URL pattern)
DATABASE_URL=postgres://postgres:localpass@localhost:5432/myproject

# Cache (django-environ URL pattern)
CACHE_URL=redis://localhost:6379/1

# Email
EMAIL_BACKEND=django.core.mail.backends.smtp.EmailBackend
EMAIL_HOST=smtp.gmail.com
EMAIL_PORT=587
EMAIL_USE_TLS=True
EMAIL_HOST_USER=user@example.com
EMAIL_HOST_PASSWORD=app-password

Python-specific conversion considerations:

1. django-environ URL patterns. Instead of separate host, port, user, password, name keys, django-environ uses a single URL: DATABASE_URL=postgres://user:pass@host:port/dbname. This is more compact but loses granularity.

2. Boolean convention. Python's True/False capitalization is often used in ENV files targeting Python apps (vs lowercase true/false for other ecosystems). The django-environ library accepts both.

3. List handling. DJANGO_ALLOWED_HOSTS=localhost,127.0.0.1 is parsed with env.list('DJANGO_ALLOWED_HOSTS') which splits on commas.

4. Type casting with django-environ:

import environ
env = environ.Env(
    DEBUG=(bool, False),           # Cast to bool, default False
    EMAIL_PORT=(int, 587),         # Cast to int, default 587
    ALLOWED_HOSTS=(list, []),      # Cast to list, default empty
)

Flask/FastAPI equivalent:

# Flask config.yml
flask:
  secret_key: dev-key
  sqlalchemy_database_uri: "sqlite:///app.db"
  max_content_length: 16777216

FLASK_SECRET_KEY=dev-key
SQLALCHEMY_DATABASE_URI=sqlite:///app.db
MAX_CONTENT_LENGTH=16777216

Key pattern: Python frameworks typically expect UPPER_SNAKE_CASE ENV variable names that match the YAML key hierarchy with prefixes removed (e.g., django.secret_key -> DJANGO_SECRET_KEY or just SECRET_KEY).