Decouple helps you to organize your settings so that you can change parameters without having to redeploy your app.
It also makes easy for you to:
It was originally designed for Django, but became an independent generic tool for separating settings from code.
Web framework’s settings stores many different kinds of parameters:
The first 2 are project settings the last 3 are instance settings.
You should be able to change instance settings without redeploying your app.
Envvars works, but since os.environ only returns strings, it’s tricky.
Let’s say you have an envvar DEBUG=False. If you run:
if os.environ['DEBUG']: print True else: print False
It will print True, because os.environ['DEBUG'] returns the string "False". Since it’s a non-empty string, it will be evaluated as True.
Decouple provides a solution that doesn’t look like a workaround: config('DEBUG', cast=bool).
pip install python-decouple
On your settings.py.
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)
Decouple supports both .ini and .env files.
Simply create a settings.ini next to your configuration module in the form:
[settings] DEBUG=True TEMPLATE_DEBUG=%(DEBUG)s SECRET_KEY=ARANDOMSECRETKEY DATABASE_URL=mysql://myuser:mypassword@myhost/mydatabase PERCENTILE=90%%
Note: Since ConfigParser supports string interpolation, to represent the character % you need to escape it as %%.
Simply create a .env text file on your repository’s root directory in the form:
DEBUG=True TEMPLATE_DEBUG=True SECRET_KEY=ARANDOMSECRETKEY DATABASE_URL=mysql://myuser:mypassword@myhost/mydatabase PERCENTILE=90%
Given that I have a .env file at my repository root directory, here is a snippet of my settings.py.
I also recommend using unipath and dj-datatabase-url.
# 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) # ...
On the above example, all configuration parameters except SECRET_KEY = config('SECRET_KEY') have a default value to fallback if it does not exist on the .env file.
If SECRET_KEY is not present on the .env, decouple will raise an UndefinedValueError.
This fail fast policy helps you avoid chasing misbehaviors when you eventually forget a parameter.
Decouple is made of 5 classes:
Coordinates all the configuration retrieval.
Can read values from ini files.
Can read .env files and when a parameter does not exist there,
it tries to find it on os.environ.This process does not change nor add any environment variables.
Can only read values from os.environ.
Detects which configuration repository you’re using.
It recursively searches up your configuration module path looking for a
settings.ini or a .env file.
The config object is an instance of AutoConfig to improve decouple‘s usage.
The MIT License (MIT)
Copyright (c) 2013 Henrique Bastos <henrique at bastos dot net>
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