Class Method Decorator

Part of the Object Oriented Programming section of Coddy's Python journey — lesson 12 of 64.

The @classmethod decorator creates methods that receive the class itself as the first parameter (cls) instead of an instance (self).

Here is an example of a class with class methods:

class Student:
    school_name = "Python Academy"
    student_count = 0
    
    def __init__(self, name):
        self.name = name
        Student.student_count += 1
    
    @classmethod
    def get_school_info(cls):
        return f"School: {cls.school_name}, Students: {cls.student_count}"
    
    @classmethod
    def create_guest_student(cls):
        return cls("Guest")

Call class methods using the class name:

info = Student.get_school_info()
print(info)

Create some students:

alice = Student("Alice")
bob = Student("Bob")

updated_info = Student.get_school_info()
print(updated_info)

Use class methods as alternative constructors:

guest = Student.create_guest_student()
print(guest.name)
print(Student.get_school_info())

Output:

School: Python Academy, Students: 0
School: Python Academy, Students: 2
Guest
School: Python Academy, Students: 3

Class methods can also be called from instances:

alice = Student("Alice")
info_from_instance = alice.get_school_info()
print(info_from_instance)

Output:

School: Python Academy, Students: 1

Key Point: Use @classmethod when you need to access class attributes or create alternative ways to construct objects. The first parameter is cls (the class itself), not self.

Try it yourself

This lesson doesn't include a code challenge.