7.1. Classes and Objects in Python: Introduction to Classes and Objects

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Python, as an object-oriented programming language, uses concepts of classes and objects as one of its main tools for structuring code. In the context of this course on building systems with Python and Django, it is critical to understand these concepts and how they are applied in Python.

1. What are Classes and Objects?

Classes and objects are fundamental concepts in object-oriented programming (OOP). A class is like a blueprint or blueprint from which objects are created. It defines a set of attributes that will characterize any object that is molded from the class. Attributes are data members (class variables and instance variables) and methods, accessed via dot notation.

Objects, on the other hand, are instances of a class. When a class is defined, only the description for the object is defined. Therefore, no memory space is allocated. However, when an object is created, memory space is allocated.

2. Classes in Python

In Python, defining a class is quite simple. It starts with the keyword 'class', followed by the name of the class and a colon. The class name generally follows the CamelCase convention. Within the class definition, you can define attributes and methods.

class MyClass:
    attribute="value"
    
    def method(self):
        return "Hello world!"

In this example, 'MyClass' has an attribute called 'attribute' and a method called 'method'. The 'self' in the method is a reference to the current object and is used to access variables belonging to the class.

3. Objects in Python

To create an object (or instance) of a class, you simply call the class name as if it were a function. For example:

object = MyClass()

This creates a new object of class 'MyClass'. You can access object attributes and methods using dot notation:

print(object.attribute) # Output: "value"
print(object.method()) # Output: "Hello world!"

4. Attributes and Methods

Attributes are like variables that belong to an instance of a class. They can be defined in the __init__ method, which is called automatically when an object is created:

class MyClass:
    def __init__(self):
        self.attribute = "value"

Methods are like functions that belong to an instance of a class. They can access and modify instance attributes:

class MyClass:
    def __init__(self):
        self.attribute = "value"
    
    def method(self):
        self.attribute = "new value"

In short, classes and objects in Python are powerful tools that allow you to structure code efficiently and intuitively. They are fundamental to object-oriented programming and are essential for building systems with Python and Django.

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387.2. Classes and Objects in Python: Attributes and Methods of a Class