Returning Instances of a Different Class

00:01 Returning Instances of a Different Class. Returning an object of a different class is a requirement that can raise the need for a custom implementation of .__new__(). However, you should be careful because in this case, Python skips the initialization step entirely.

00:17 So, you’ll have the responsibility of taking the newly created object into a valid state before using it in your code. On-screen, you’ll see an example where the Pet class uses .__new__() to return instances of randomly selected classes.

00:37 Here, Pet provides a .__new__() method that creates a new instance by randomly selecting a class from a list of existing classes.

01:26 Here’s how you can use this Pet class as a factory of pet objects. Every time you instantiate Pet, you get a random object from a different class.

01:40 This result is possible because there’s no restriction on the object that .__new__() can return. Using .__new__() in such a way transforms a class into a flexible and powerful factory of objects, not limited to instances of itself.

01:55 Finally, note how the .__init__() method of Pet never runs. And that’s because Pet.__new__() always returns objects of a different class rather than of Pet itself.

02:11 In the next section of the course, you’ll take a look at how to allow only a single instance of a class.