mo-kwargs 2.31.19025

More KWARGS! Let call parameters override kwargs

More KWARGS!

Motivation

Extensive use of dependency injection, plus managing the configuration for each of the components being injected, can result in some spectacularly complex system configuration. One way to reduce the complexity is to use configuration templates that contain useful defaults, and then overwrite the properties that need to be changed for the desired configuration. @override has been created to provide this templating system for Python function calls (primarily class constructors).

@override will decorate a function to accept a kwargs parameter which is just like **kwargs, but the call parameters will override the properties in kwargs, rather than raise duplicate key exceptions.

Example

We decorate the login() function with @override. In this case, username is a required parameter, and password will default to None. The kwargs parameter should always default to None so that it's not required.

	@override
	def login(username, password=None, kwargs=None):
		pass

Define some dicts for use with our kwargs parameter:

	creds = {"userame": "ekyle", "password": "password123"}
	alt_creds = {"username": "klahnakoski"}

The simplest case is when we use kwargs with no overrides

	login(kwargs=creds)
	# SAME AS
	login(**creds)
	# SAME AS
	login(username="ekyle", password="password123")

You may override any property in kwargs: In this case it is password

	login(password="123", kwargs=creds)
	# SAME AS
	login(username="ekyle", password="123")

There is no problem with overriding everything in kwargs:

	login(username="klahnakoski", password="asd213", kwargs=creds)
	# SAME AS
	login(username="klahnakoski", password="asd213")

You may continue to use **kwargs; which provides a way to overlay one parameter template (creds) with another (alt_creds)

	login(kwargs=creds, **alt_creds)
	# SAME AS
	login(username="klahnakoski", password="password123")