The Anatomy of a Python Class

A Python class is a template for creating objects, which are instances of the class. These objects have their own attributes (variables) and methods (functions), which are defined in the class. In this article, we will take a detailed look at the anatomy of a Python class, including its components and how they work together.

The Basic Class Structure

The basic structure of a Python class is as follows:

The class is defined using the "class" keyword, followed by the class name. The class name should be in CamelCase (i.e., the first letter of each word is capitalized), and it should be descriptive of the class's purpose.

The first method defined in a class is the __init__ method. This method is a special method that is called when an object of the class is created. The __init__ method is used to initialize the attributes of the object. The first parameter of the __init__ method is always "self," which refers to the object being created. self.attribute = value inside the __init__ method will create an attribute for the class object.

Here's an example of a Python class that defines a simple "Person" class with a name attribute and a "greet" method:

In this example, the __init__ method initializes the name attribute of the Person object with the value passed as a parameter. The greet method simply prints out a greeting with the person's name. It is an instance method. We are going to look at instance methods later.

To create an object of this class and call its methods, we would do the following:

Instance Methods

The class can also have other methods. One of them is an instance method. An instance method is a method that is bound to an instance of a class, and not the class itself. The first parameter is always "self," which refers to the object the method is being called on. It can access and modify the instance variables, and it can also access class variables (we will look at class variables next). Here's an example of an instance method being used in a class:

Class Methods and Class Variables

Class methods are defined using the @classmethod decorator, which takes "cls" (the class name) as its first parameter. In addition to the methods, a class can also have class variables. Class variables are variables that are shared by all objects of the class, while class methods are methods that are called on the class itself rather than on an object. Class variables are defined outside of any method, usually at the top of the class definition. Class methods can access class variables. Here is an example:

Magic Methods

In addition to the class and instance variables and methods, Python classes also have special methods, also known as magic methods. These methods have double underscores at the beginning and end of their names (e.g. __init__, __str__, __add__). These special methods allow us to customize the behavior of the class when certain operations are performed on it. For example, the __str__ method is called when we use the built-in print() function on an object of the class, and allows us to define what should be printed. See example below:

In this example, when we use the print() function on the p1 object, it calls the __str__ method defined in the class. This method returns the string "Person: Mike," which is then printed by the print() function.

Another example of a special method is the __add__ method, which allows us to customize the behavior of the + operator when used on objects of the class. Here's an example:

In this instance, when the + operator is used on the v1 and v2 objects, the class-specified __add__ method is invoked. The return value of this method is a new Vector object that has x and y values equal to the sum of the x and y values of the two original Vector objects.

These are just a few of the numerous special methods that Python offers. These unique methods allow us to modify a class' behavior, enhancing its strength and adaptability.

Conclusion

In conclusion, a Python class is a template for creating objects, which are instances of the class. Classes can have methods and variables. The class defines these methods and variables, which can be used to alter how the class and its objects behave. To write Python code that is effective and flexible, it is crucial to comprehend the anatomy of a Python class. Thank you for reading. Please share this story and subscribe to this newsletter if you are not yet a subscriber. You can also follow me on LinkedIn.