python-decouple 3.8

Python Decouple: Strict separation of settings from code

Decouple helps you to organize your settings so that you can change parameters without having to redeploy your app.

It also makes it easy for you to:

1. store parameters in ini or .env files;

2. define comprehensive default values;

3. properly convert values to the correct data type;

4. have only one configuration module to rule all your instances.

It was originally designed for Django, but became an independent generic tool for separating settings from code.

Why?

The settings files in web frameworks store many different kinds of parameters:

• Locale and i18n;

• Middlewares and Installed Apps;

• Resource handles to the database, Memcached, and other backing services;

• Credentials to external services such as Amazon S3 or Twitter;

• Per-deploy values such as the canonical hostname for the instance.

The first 2 are project settings and the last 3 are instance settings.

You should be able to change instance settings without redeploying your app.

if os.environ['DEBUG']:
    print True
else:
    print False

Usage

Install:

pip install python-decouple

Then use it on your settings.py.

1. Import the config object:

   from decouple import config

2. Retrieve the configuration parameters:

   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)

from decouple import config
config.encoding = 'cp1251'
SECRET_KEY = config('SECRET_KEY')

import locale
from decouple import config
config.encoding = locale.getpreferredencoding(False)
SECRET_KEY = config('SECRET_KEY')

[settings]
DEBUG=True
TEMPLATE_DEBUG=%(DEBUG)s
SECRET_KEY=ARANDOMSECRETKEY
DATABASE_URL=mysql://myuser:mypassword@myhost/mydatabase
PERCENTILE=90%%
#COMMENTED=42

DEBUG=True
TEMPLATE_DEBUG=True
SECRET_KEY=ARANDOMSECRETKEY
DATABASE_URL=mysql://myuser:mypassword@myhost/mydatabase
PERCENTILE=90%
#COMMENTED=42

# coding: utf-8
from decouple import config
from unipath import Path
from dj_database_url import parse as db_url


BASE_DIR = Path(__file__).parent

DEBUG = config('DEBUG', default=False, cast=bool)
TEMPLATE_DEBUG = DEBUG

DATABASES = {
    'default': config(
        'DATABASE_URL',
        default='sqlite:///' + BASE_DIR.child('db.sqlite3'),
        cast=db_url
    )
}

TIME_ZONE = 'America/Sao_Paulo'
USE_L10N = True
USE_TZ = True

SECRET_KEY = config('SECRET_KEY')

EMAIL_HOST = config('EMAIL_HOST', default='localhost')
EMAIL_PORT = config('EMAIL_PORT', default=25, cast=int)
EMAIL_HOST_PASSWORD = config('EMAIL_HOST_PASSWORD', default='')
EMAIL_HOST_USER = config('EMAIL_HOST_USER', default='')
EMAIL_USE_TLS = config('EMAIL_USE_TLS', default=False, cast=bool)

# ...

DEBUG=True python manage.py

How does it work?

Decouple always searches for Options in this order:

1. Environment variables;

2. Repository: ini or .env file;

3. Default argument passed to config.

There are 4 classes doing the magic:

• Config

  Coordinates all the configuration retrieval.

• RepositoryIni

  Can read values from os.environ and ini files, in that order.

  Note: Since version 3.0 decouple respects unix precedence of environment variables over config files.

• RepositoryEnv

  Can read values from os.environ and .env files.

  Note: Since version 3.0 decouple respects unix precedence of environment variables over config files.

• AutoConfig

  This is a lazy Config factory that detects which configuration repository you’re using.

  It recursively searches up your configuration module path looking for a settings.ini or a .env file.

  Optionally, it accepts search_path argument to explicitly define where the search starts.

The config object is an instance of AutoConfig that instantiates a Config with the proper Repository on the first time it is used.

>>> os.environ['DEBUG'] = 'False'
>>> config('DEBUG', cast=bool)
False

>>> os.environ['EMAIL_PORT'] = '42'
>>> config('EMAIL_PORT', cast=int)
42

>>> os.environ['ALLOWED_HOSTS'] = '.localhost, .herokuapp.com'
>>> config('ALLOWED_HOSTS', cast=lambda v: [s.strip() for s in v.split(',')])
['.localhost', '.herokuapp.com']

>>> os.environ['SECURE_PROXY_SSL_HEADER'] = 'HTTP_X_FORWARDED_PROTO, https'
>>> config('SECURE_PROXY_SSL_HEADER', cast=Csv(post_process=tuple))
('HTTP_X_FORWARDED_PROTO', 'https')

>>> from decouple import Csv
>>> os.environ['ALLOWED_HOSTS'] = '.localhost, .herokuapp.com'
>>> config('ALLOWED_HOSTS', cast=Csv())
['.localhost', '.herokuapp.com']

>>> from decouple import Csv
>>> config('ALLOWED_HOSTS', default='127.0.0.1', cast=Csv())
['127.0.0.1']

>>> os.environ['LIST_OF_INTEGERS'] = '1,2,3,4,5'
>>> config('LIST_OF_INTEGERS', cast=Csv(int))
[1, 2, 3, 4, 5]

>>> os.environ['COMPLEX_STRING'] = '%virtual_env%\t *important stuff*\t   trailing spaces   '
>>> csv = Csv(cast=lambda s: s.upper(), delimiter='\t', strip=' %*')
>>> csv(os.environ['COMPLEX_STRING'])
['VIRTUAL_ENV', 'IMPORTANT STUFF', 'TRAILING SPACES']

>>> os.environ['SECURE_PROXY_SSL_HEADER'] = 'HTTP_X_FORWARDED_PROTO, https'
>>> config('SECURE_PROXY_SSL_HEADER', cast=Csv(post_process=tuple))
('HTTP_X_FORWARDED_PROTO', 'https')

>>> from decouple import config, Choices
>>> os.environ['CONNECTION_TYPE'] = 'usb'
>>> config('CONNECTION_TYPE', cast=Choices(['eth', 'usb', 'bluetooth']))
'usb'

>>> os.environ['CONNECTION_TYPE'] = 'serial'
>>> config('CONNECTION_TYPE', cast=Choices(['eth', 'usb', 'bluetooth']))
Traceback (most recent call last):
 ...
ValueError: Value not in list: 'serial'; valid values are ['eth', 'usb', 'bluetooth']

>>> os.environ['SOME_NUMBER'] = '42'
>>> config('SOME_NUMBER', cast=Choices([7, 14, 42], cast=int))
42

>>> USB = 'usb'
>>> ETH = 'eth'
>>> BLUETOOTH = 'bluetooth'
>>>
>>> CONNECTION_OPTIONS = (
...        (USB, 'USB'),
...        (ETH, 'Ethernet'),
...        (BLUETOOTH, 'Bluetooth'),)
...
>>> os.environ['CONNECTION_TYPE'] = BLUETOOTH
>>> config('CONNECTION_TYPE', cast=Choices(choices=CONNECTION_OPTIONS))
'bluetooth'

Contribute

Your contribution is welcome.

Setup your development environment:

git clone git@github.com:henriquebastos/python-decouple.git
cd python-decouple
python -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt
tox

Decouple supports both Python 2.7 and 3.6. Make sure you have both installed.

I use pyenv to manage multiple Python versions and I described my workspace setup on this article: The definitive guide to setup my Python workspace

You can submit pull requests and issues for discussion. However I only consider merging tested code.

License

The MIT License (MIT)

Copyright (c) 2017 Henrique Bastos <henrique at bastos dot net>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.