Python Classes and Objects: Creating and Using Classes

Learn about Python's object-oriented programming approach. Discover how to create classes and objects using the class keyword, and see examples of defining a class and instantiating objects.

Python Classes and Objects

Python is an object-oriented programming language. Almost everything in Python is an object, with its properties and methods. A class is like an object constructor or a "blueprint" for creating objects.

Create a Class

To create a class, use the keyword class:

class MyClass:
    x = 10
        

Create an Object

Now we can use the class named MyClass to create objects:

p1 = MyClass()
print(p1.x)
        

10
        

The __init__() Function

All classes have a function called __init__(), which is always executed when the class is being initiated. Use the __init__() function to assign values to object properties, or other operations that are necessary when the object is being created:

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

p1 = Person("Alice", 25)
print(p1.name)
print(p1.age)
        

Alice
25
        

The __str__() Function

The __str__() function controls what should be returned when the class object is represented as a string. If the __str__() function is not set, the string representation of the object is returned:

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

p1 = Person("Alice", 25)
print(p1)
        

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def __str__(self):
        return f"{self.name}({self.age})"

p1 = Person("Alice", 25)
print(p1)
        

Alice(25)
        

Object Methods

Objects can also contain methods. Methods in objects are functions that belong to the object. Let us create a method in the Person class:

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def myfunc(self):
        print("Hello, my name is " + self.name)

p1 = Person("Alice", 25)
p1.myfunc()
        

Hello, my name is Alice
        

The self Parameter

The self parameter is a reference to the current instance of the class, and is used to access variables that belong to the class. It does not have to be named self, you can call it whatever you like, but it has to be the first parameter of any function in the class:

class Person:
    def __init__(mysillyobject, name, age):
        mysillyobject.name = name
        mysillyobject.age = age

    def myfunc(abc):
        print("Hello, my name is " + abc.name)

p1 = Person("Alice", 25)
p1.myfunc()
        

Hello, my name is Alice
        

Modify Object Properties

You can modify properties on objects like this:

p1.age = 30

Delete Object Properties

You can delete properties on objects by using the del keyword:

del p1.age

Delete Objects

You can delete objects by using the del keyword:

del p1

The pass Statement

Class definitions cannot be empty, but if you for some reason have a class definition with no content, put in the pass statement to avoid getting an error:

class Person: pass