What is a static function in python?

In this article, we will cover the basic difference between the class method vs Static method in Python and when to use the class method and static method in python.

What is Class Method in Python? 

The @classmethod decorator is a built-in function decorator that is an expression that gets evaluated after your function is defined. The result of that evaluation shadows your function definition. A class method receives the class as an implicit first argument, just like an instance method receives the instance 

Syntax Python Class Method: 

class C(object):
    @classmethod
    def fun(cls, arg1, arg2, ...):
       ....
fun: function that needs to be converted into a class method
returns: a class method for function.

• A class method is a method that is bound to the class and not the object of the class.
• They have the access to the state of the class as it takes a class parameter that points to the class and not the object instance.
• It can modify a class state that would apply across all the instances of the class. For example, it can modify a class variable that will be applicable to all the instances.

What is the Static Method in Python?

A static method does not receive an implicit first argument. A static method is also a method that is bound to the class and not the object of the class. This method can’t access or modify the class state. It is present in a class because it makes sense for the method to be present in class.

Syntax Python Static Method: 

class C(object):
    @staticmethod
    def fun(arg1, arg2, ...):
        ...
returns: a static method for function fun.

Class method vs Static Method

The difference between the Class method and the static method is:

• A class method takes cls as the first parameter while a static method needs no specific parameters.
• A class method can access or modify the class state while a static method can’t access or modify it.
• In general, static methods know nothing about the class state. They are utility-type methods that take some parameters and work upon those parameters. On the other hand class methods must have class as a parameter.
• We use @classmethod decorator in python to create a class method and we use @staticmethod decorator to create a static method in python.

When to use the class or static method?

• We generally use the class method to create factory methods. Factory methods return class objects ( similar to a constructor ) for different use cases.
• We generally use static methods to create utility functions.

How to define a class method and a static method?

To define a class method in python, we use @classmethod decorator, and to define a static method we use @staticmethod decorator. 
Let us look at an example to understand the difference between both of them. Let us say we want to create a class Person. Now, python doesn’t support method overloading like C++ or Java so we use class methods to create factory methods. In the below example we use a class method to create a person object from birth year.

As explained above we use static methods to create utility functions. In the below example we use a static method to check if a person is an adult or not. 

Below is the complete Implementation 

Python3

from datetime import date

class Person:

    def __init__(self, name, age):

        self.name = name

        self.age = age

    @classmethod

    def fromBirthYear(cls, name, year):

        return cls(name, date.today().year - year)

    @staticmethod

    def isAdult(age):

        return age > 18

person1 = Person('mayank', 21)

person2 = Person.fromBirthYear('mayank', 1996)

print(person1.age)

print(person2.age)

print(Person.isAdult(22))

Output:

21
25
True

Auxiliary Space: O(1)

What is a static function?

How do you make a function static in Python?

When should I use static method in Python?