🐍 Environment variables in Python

Read The Twelve Factor App for context.

Note: Sorted by number of downloads.

Pydantic

• Recommended by FastAPI

from pydantic import BaseSettings


class Settings(BaseSettings):
    app_name: str = "Awesome API"
    admin_email: str
    items_per_user: int = 50

settings = Settings(_env_file='.env')

Python-dotenv

• Recommended by Flask
• Used internally by Pydantic, environs, Dynaconf, etc.

from dotenv import load_dotenv, dotenv_values

load_dotenv()  # read using os.environ["KEY"]

Does NOT handle types.

Django-environ

import environ
env = environ.Env(
    # set casting, default value
    DEBUG=(bool, False)
)
# reading .env file
environ.Env.read_env()

# False if not in os.environ
DEBUG = env('DEBUG')

# Raises django's ImproperlyConfigured exception if SECRET_KEY not in os.environ
SECRET_KEY = env('SECRET_KEY')

# Parse database connection url strings like psql://user:[email protected]:8458/db
DATABASES = {
    # read os.environ['DATABASE_URL'] and raises ImproperlyConfigured exception if not found
    'default': env.db(),
    # read os.environ['SQLITE_URL']
    'extra': env.db('SQLITE_URL', default='sqlite:////tmp/my-tmp-sqlite.db')
}

CACHES = {
    # read os.environ['CACHE_URL'] and raises ImproperlyConfigured exception if not found
    'default': env.cache(),
    # read os.environ['REDIS_URL']
    'redis': env.cache('REDIS_URL')
}

Mainly for Django.

Python Decouple

from decouple import config

SECRET_KEY = config('SECRET_KEY')
DEBUG = config('DEBUG', default=False, cast=bool)
EMAIL_HOST = config('EMAIL_HOST', default='localhost')
EMAIL_PORT = config('EMAIL_PORT', default=25, cast=int)

Environs

• Used by cookiecutter-flask

from environs import Env

env = Env()
env.read_env()  # read .env file, if it exists
# required variables
gh_user = env("GITHUB_USER")  # => 'sloria'
secret = env("SECRET")  # => raises error if not set

# casting
max_connections = env.int("MAX_CONNECTIONS")  # => 100
ship_date = env.date("SHIP_DATE")  # => datetime.date(1984, 6, 25)
ttl = env.timedelta("TTL")  # => datetime.timedelta(0, 42)
log_level = env.log_level("LOG_LEVEL")  # => logging.DEBUG

# providing a default value
enable_login = env.bool("ENABLE_LOGIN", False)  # => True
enable_feature_x = env.bool("ENABLE_FEATURE_X", False)  # => False

# parsing lists
gh_repos = env.list("GITHUB_REPOS")  # => ['webargs', 'konch', 'ped']
coords = env.list("COORDINATES", subcast=float)  # => [23.3, 50.0]

# parsing dicts
gh_repos_priorities = env.dict(
    "GITHUB_REPO_PRIORITY", subcast_values=int
)  # => {'webargs': 2, 'konch': 3}

Dynaconf

# config.py
from dynaconf import Dynaconf

settings = Dynaconf(
    settings_files=['settings.toml', '.secrets.toml'],
)

assert settings.key == "value"

# settings.toml
key = "value"
a_boolean = false
number = 1234
a_float = 56.8
a_list = [1, 2, 3, 4]
a_dict = {hello="world"}

[a_dict.nested]
other_level = "nested value"

# .secrets.toml
password = "s3cr3t"
token = "dfgrfg5d4g56ds4gsdf5g74984we5345-"
message = "This file doesn't go to your pub repo"

export DYNACONF_NUMBER=789
export DYNACONF_FOO=false

Also loads .env file automatically.

Hydra

• By Facebook

Mainly for Machine Learning.