Configuration

Describing Configuration Handling

• Applications need some kind of configuration
• There are different settings depending on the application environment

• These settings include:

  • Toggling the debug mode
  • Setting the secret key
  • Setting environment-specific things
• Flask sets configuration values in the config attribute
• Specifically, there is a config attribute for every Flask object
• This is where we can set our own configurations

Basics of Configuration

• The config is a subclass of a dictionary
• Implying, it can be modified like any dictionary
• The following is an example of this behavior:

>>> app = Flask(__name__)
>>> app.config['TESTING'] = True

• Some configuration values are forwarded to the Flask object
• This is so we can read and write from the object
• The following is an example:

>>> app.testing = True

• The update method updates multiple keys at once:

>>> app.config.update(
...     TESTING=True
...     SECRET_KEY=b'_5#y2L"F4Q8z\n\xec]/'
... )

Configuration Best Practices

• Create an application in a function

• Register blueprints to the application

  • This allows us to create multiple instance of our application with different configurations
  • This makes unit testing much easier
• Never write code that needs configuration at import time

Creating Development and Production Environments

• Most applications need more than one configuartion

• There should be two separate configurations for:

  • Production
  • Development
  • Testing
• We can do either of the following approach:
• Create separate config files

>>> from config import PROD_SETTINGS
>>> from config import TEST_SETTINGS

>>> prod = Flask(__name__)
>>> prod.config.from_object('PROD_SETTINGS')

>>> test = Flask(__name__)
>>> test.config.from_object('TEST_SETTINGS')

2. Create configuration classes

>>> class Config(object):
...     DEBUG = False
...     TESTING = False
...     DATABASE_URI = 'sqlite:///:memory:'
>>> class ProdConfig(Config):
...     DATABASE_URI = 'mysql://user@localhost/foo'
>>> class TestConfig(Config):
...     DEBUG = True

>>> prod.config.from_object('ProdConfig')
>>> test.config.from_object('TestConfig')

References

• Details about Configuration Handling in Flask