What are Objects?

Objects are containers that hold a collection of attributes and functions. Think of objects as real-world entities that have properties (attributes) and can perform actions (methods). For example, you might create an application that tracks dogs.

Object Attributes (Properties)

For each dog you are tracking, you might create an object. Each dog object would have a collection of attributes like:

• Color: The dog’s fur color
• Age: How old the dog is
• Breed: What type of dog it is

Object Methods (Actions)

Each dog object also has actions associated with it. For example, you might:

• Take the dog for a walk
• Cut the dog’s hair
• Give the dog a bath

Working with Objects – Example

Let’s assume you have imported a library that gives you access to an object called dog. Here’s how you would work with it:

# Create a new dog object named Max
mydog = dog("Max")

# Set Max's breed to Chihuahua
mydog.breed = "Chihuahua"

# Shorten Max's hair length
mydog.cut_hair(2)

# Look at all of the attributes
print(mydog.name)
print(mydog.breed)
print(mydog.hairlength)

What are Classes?

As we discussed in the previous section, an object is a container that holds various attributes and functions. A class is the code that you use to create an object. Think of a class as a blueprint or template for creating objects.

Creating a Basic Class

To create a new class, we use the keyword class. Let’s create a new class called dog with two attributes: breed and name:

class dog:
    name = ""
    breed = ""

# Create a new instance of this class
mydog = dog()

# Set the name and breed
mydog.name = "Max"
mydog.breed = "Chihuahua"

# Print the dog's name
print(mydog.name)

Adding an Initialization Function

We probably want to treat the name of the dog as a unique attribute for each of our dogs and ensure that all dogs have names. To do this, we need to add an __init__ function that will be called every time we create a new dog object:

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

# Create a new dog object named Max
mydog = dog("Max")

print(mydog.name)  # Output: Max

Adding Methods to Classes

There are various things we will do with our dog. Perhaps we need to cut our dog’s hair on occasion. Let’s add a new variable called hairlength and a function called cut_hair:

class dog:
    breed = ""

    # Add hairlength variable to init function
    def __init__(self, name):
        self.name = name
        self.hairlength = 10

    # Declare hair cutting function
    def cut_hair(self, howmuch):
        self.hairlength = self.hairlength - howmuch

# Create a new Dog object named Max
mydog = dog("Max")

# Call the function to cut the dog's hair
mydog.cut_hair(2)

# Print how long the hair length is now
print(mydog.hairlength)  # Output: 8

As you can see above, we start by creating a new dog object, then we call the cut_hair function. The default value in the init function is to have a hairlength of 10. So the output from the print command should be 8.

When Should You Use Objects and Classes?

Objects and classes allow you to break up your application into smaller, manageable pieces. These smaller pieces can be independently modified and tested. If you have done things right, you can modify one class without worrying about breaking another class.

Key Benefits of Object-Oriented Programming

• Modularity: Break complex programs into smaller, manageable pieces
• Reusability: Create classes once and use them multiple times
• Maintainability: Easier to modify and debug isolated components
• Scalability: Better organization for larger teams and bigger projects

Best Practices

As your programs get bigger, and you work on larger teams, organization becomes increasingly important. Generally, the rule is that classes should only do one thing, and do that one thing really well. Think of each class as a mini-program within your main program.

Summary

Today we have discussed what Objects and Classes are in Python. We have covered how to use objects, how to create classes, and how the two topics are inter-related. Understanding these concepts is fundamental to writing effective Python code that can scale as your applications grow.

Key Takeaways

• Objects are containers that hold attributes and methods
• Classes are blueprints for creating objects
• Use the __init__ method to initialize object attributes
• Object-oriented programming improves code organization and maintainability

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