Why instance attributes don't always have to be passed in?

Hi Julius Kucinskas

Instance attributes don't have to be passed in when an instance is created. The reason why depends on the class you are creating, but essentially being able to pass in values gives you the ability to make each instance unique. Some attributes like maybe a name or age will probably be unique to each instance, while other attributes may not need to be unique.

Let's look at an example:

class Dog:
    def __init__(self, name, age):
        self.name = name
        self.age = age
        self.sound = 'Woof woof!'

In the class above, I created 3 instance attributes, 2 of which are passed in when an instance is created, like this: jethro = Dog('Jethro', 2). The last attribute, self.sound does not need to be passed in. All dog instances will be created with this sound.

If I need to change Jethro's sound, I can still do that by accessing the attribute and setting it equal to something else. jethro.sound = 'Boof!'

I can also still access all of these in a method:

class Dog:
    def __init__(self, name, age):
        self.name = name
        self.age = age
        self.sound = 'Woof woof!'

    def about(self):
        return. f'{self.name} is {self.age} old and says "{self.sound}"'

Hopefully this helps. Let me know if you still have questions.