Python Programming for Lazy Beginners: A Simple and Easy Tutorial

CHAPTER 12

This creates an object called my_account that has an account_number of "123456789", a balance of 1000, and an account_type of "checking". We can then use the deposit() and withdraw() methods to modify the balance attribute as needed.

Overall, defining and creating classes in Python is similar to creating a set of Lego instructions and building the object. You define the attributes and methods in the class, and then create instances of the class that can be used in your code.

Instantiating objects from classes

When you create an instance of the class, you are essentially following the recipe to create the object.

Let's say you have a class called Dog, which defines the attributes and behaviors of a dog. To create an instance of this class, you would use the class name followed by parentheses, like so:

class Dog:
    def __init__(self, name, breed):
        self.name = name
        self.breed = breed

my_dog = Dog("Fido", "Golden Retriever")

In this example, we defined a Dog class with an __init__() method that initializes the name and breed attributes for each instance of the class. We then created an instance of the class called my_dog and passed in the arguments "Fido" and "Golden Retriever", which were used to set the name and breed attributes for this instance.

Now that we have an instance of the Dog class, we can access its attributes and methods. For example, we could print out the name and breed of the dog like so:

print(my_dog.name)
print(my_dog.breed)

In summary, instantiating objects from classes in Python is like following a recipe to make a cake. You use the class name followed by parentheses to create an instance of the class, and then you can access the attributes and methods of that instance to do whatever you need to do with it.

Class methods and attributes

Imagine you're running a bakery, and you have a recipe for making cupcakes. The recipe contains instructions for mixing the ingredients, baking the cupcakes, and decorating them with frosting and sprinkles. In object-oriented programming, you can think of the recipe as a class, and the cupcakes as instances of that class.

Now, let's say you want to add a new flavor of cupcake to your menu. You could create a new recipe from scratch, but that would be time-consuming and inefficient. Instead, you could use your existing recipe as a base, and just modify it slightly to create the new flavor. In object-oriented programming, you can do something similar using class methods and attributes.

A class attribute is a variable that is shared among all instances of the class. This is useful for storing information that is common to all instances. For example, you might have a Bakery class with a class attribute called location that stores the address of your bakery:

class Bakery:
    location = "123 Main St."

    def __init__(self, name):
        self.name = name

In this example, the location attribute is a class attribute, because it is defined outside of any method and is shared among all instances of the Bakery class. The __init__() method initializes the name attribute for each instance of the class.

A class method is a method that is bound to the class and not the instance. This is useful for performing operations that are related to the class as a whole, rather than to individual instances. For example, you might have a Cupcake class with a class method called bake() that handles the baking process: