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Load configuration variables from a file or environment

Project description

Define configuration variables and load them from environment or JSON/YAML file. Also generates initial configuration files and documentation for your defined configuration.


pip install goodconf or pip install goodconf[yaml] if parsing/generating YAML files is required.

Quick Start

Let’s use configurable Django settings as an example.

First, create a file in your project’s directory, next to

import base64
import os

from goodconf import GoodConf, Value

class Config(GoodConf):
    "Configuration for My App"
    DEBUG = Value(default=False, help="Toggle debugging.")
    DATABASE_URL = Value(
        help="Database connection.")
    SECRET_KEY = Value(
        initial=lambda: base64.b64encode(os.urandom(60)).decode(),
        help="Used for cryptographic signing. "

Next, use the config in your file:

import os
import dj_database_url
from .conf import Config

BASE_DIR = os.path.dirname(os.path.dirname(__file__))

config = Config(
        os.path.join(BASE_DIR, "myproject.yaml"),

DEBUG = config.DEBUG
DATABASES = {"default": dj_database_url.parse(config.DATABASE_URL)}

In your initial developer installation instructions, give some advice such as:

python -c "import myproject; print(myproject.config.generate_yaml(DEBUG=True))" > myproject.yaml



Your subclassed GoodConf object can be initialized with the following keyword args:

The name of an environment variable which can be used for the name of the configuration file to load.
If no file is passed to the load method, try to load a configuration from these files in order.
Trigger the load method during instantiation. Defaults to False.

Use plain-text docstring for use as a header when generating a configuration file.


Declare configuration values by subclassing GoodConf and defining class attributes which are Value instances. They can be initialized with the following keyword args:

Default value if none is provided. If left unset, loading a config that fails to provide this value will raise accept RequiredValueMissing exception.
Initial value to use when generating a config
Python type to cast variable as. Defaults to type of default (if provided) or str.
Plain-text description of the value.

Django Usage

A helper is provided which monkey-patches Django’s management commands to accept a --config argument. Replace your with the following:

# Define your GoodConf in `myproject/`
from myproject import config

if __name__ == '__main__':


I took inspiration from logan (used by Sentry) and derpconf (used by Thumbor). Both, however used Python files for configuration. I wanted a safer format and one that was easier to serialize data into from a configuration management system.

Environment Variables

I don’t like working with environment variables. First, there are potential security issues:

  1. Accidental leaks via logging or error reporting services.
  2. Child process inheritance (see ImageTragick for an idea why this could be bad).

Second, in practice on deployment environments, environment variables end up getting written to a number of files (cron, bash profile, service definitions, web server config, etc.). Not only is it cumbersome, but also increases the possibility of leaks via incorrect file permissions.

I prefer a single structured file which is explicitly read by the application. I also want it to be easy to run my applications on services like Heroku where environment variables are the preferred configuration method.

This module let’s me do things the way I prefer in environments I control, but still run them with environment variables on environments I don’t control with minimal fuss.

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