Flask-DotEnv will directly set (add, update, map as alias and eval as literal) variables from .env file, and cast them to Python native types as appropriate.

(optional)

• alias() makes alias vars
• eval() evaluate var to literal (via ast)

• https://gitlab.com/grauwoelfchen/flask-dotenv.git (main)
• https://github.com/grauwoelfchen/flask-dotenv.git

$ pip install Flask-DotEnv

from flask import Flask
from flask_dotenv import DotEnv

app = Flask(__name__)
env = DotEnv(app)

As a factory pattern.

env = DotEnv()
env.init_app(app)

class Config:
    SECRET_KEY = ":'("
    ...

    @classmethod
    def init_app(self, app)
        env = DotEnv()
        env.init_app(app)

Then in your app:

from config import Config

app = Flask(__name__)
app.config.from_object(config[config_name])

See also:

flask.Config.from_object (Flask's API documentation)

You can pass the .env file path as a second argument of init_app().

env.init_app(app, env_file="/path/to/.env", verbose_mode=True)

* Overwriting an existing config var: SECRET_KEY
* Setting an entirely new config var: DEVELOPMENT_DATABASE_URL
* Casting a denoted var as a literal: MAIL_PORT => <class 'int'>
* Making a specified var as an alias: DEVELOPMENT_DATABASE_URL -> SQLALCHEMY_DATABASE_URI
...

The alias() method takes a dict argument. Each key is the existing config var, while each value is the new alias.

env.alias(maps={
  'TEST_DATABASE_URL': 'SQLALCHEMY_DATABASE_URI',
  'TEST_HOST': 'HOST'
})

Here's an example of its use:

class Config:
    SECRET_KEY = ":'("
    ...

    @classmethod
    def init_app(self, app)
        env = DotEnv()
        env.init_app(app)

        # The following will store in `SQLALCHEMY_DATABASE_URI` the value
        # in, for example, `DEVELOPMENT_DATABASE_URL`
        prefix = self.__name__.replace('Config', '').upper()
        env.alias(maps={
            prefix + '_DATABASE_URL': 'SQLALCHEMY_DATABASE_URI'
        })


class DevelopmentConfig(Config):
    DEBUG = True
    SQLALCHEMY_DATABASE_URI = None


config = {
    'development': DevelopmentConfig
}

eval() also takes a dict argument. These keys are also the existing config var, while the values are the type they should evaluate to. If the type is something else, the config var is skipped with a log message shown.

env.eval(keys={
  'MAIL_PORT': int,
  'SETTINGS': dict
})

And here's an example of its use:

class Config:
    SECRET_KEY = ":'("
    ...

    @classmethod
    def init_app(self, app)
        env = DotEnv()
        env.init_app(app)

        # `MAIL_PORT` will be set the the integer verson of the value found there
        # using `ast.literal_eval`.
        env.eval(keys={
            MAIL_PORT: int
        })

The following lines are all valid.

SECRET_KEY="123"
USERNAME=john
DATABASE_URL='postgresql://user:password@localhost/production?sslmode=require'
FEATURES={'DotEnv': True}
# comment and blank lines are also supported

export ENV="production"
export env="staging"

Run the unit tests with:

$ python setup.py test

Inspired by:

• python-dotenv
• django-dotenv

Other packages that also set configuration variables:

• Flask-EnvConfig
• Flask-UserEnvConfig

BSD 2-Clause License