enver

Enver is a simple config / environment helper.

Collect all your config values and environment variables in a single location, so new contributors knows what variables must be set, and don't have to go searching for os.environ or os.getenv scattered throughout the code.

Features:

• Automatic validation of environment variables.
• Automatic casting to desired data type using Pydantic.
• Optional default values.
• Fails fast if a variable has no value (either default or override).
• Allows lookup using dot notation, e.g. env.DB_PASSWORD, as well as subscript (env['DB_PASSWORD']) or the get() method env.get('DB_PASSWORD').

Installation

pip install enver

Usage

Create a class that inherits from Enver, with config variables as class attributes. Putting this class in a separate config.py file might be a good idea, but is not necessary.

# config.py

from enver import Enver
from typing import Optional, List, Dict

class Config(Enver):
    MY_DB_HOST: str = "127.0.0.1"
    MY_DB_USER: str = "user"
    MY_DB_PASSWORD: str  # No default value, will be supplied as environment value.
    THIS_VAL_MIGHT_NOT_EXIST_IN_ENV: Optional[str]
    PI: float  # Read from env and converted to float, if possible.
    ENABLE_LOGGING: bool = True
    LOCATIONS: List[str] = ["/opt", "/etc"]
    MAPPING: Dict[str, float]

If environment values with the same name as any of the attributes exist, those will be used, overriding any defaults. Values will be converted to the specified type. If conversion is not possible, an exception is thrown.

Here's how to use the values:

# service.py

from .config import Config

env = Config()

user = env.MY_DB_USER
password = env.MY_DB_PASSWORD

if env.exists('FEATURE_1'):
  feature_1()

all_values = env.all()

The Enver class and any derived classes are singletons, meaning they always return the same instance:

env1 = Config()
env2 = Config()
assert env1 is env2

Which means this is fine:

user = Config().MY_DB_USER
password = Config().MY_DB_PASSWORD

Development

Dependencies for the project are managed with poetry. To install all dependencies run:

poetry install

To install pre-commit and set up its git hooks:

pip install pre-commit
pre-commit install

Now pre-commit will run automatically on every commit.