Instance method, Class method, and Static method

Instance method:

• Instance methods were called by an object which we created for the class.
• The instance object variable can be a modifier.
• Use “self” as the first parameter in the instance method.
• The “self” parameter refers to the current object.

class Student:
    # initialization method
    def __init__(self, first, last):
        #instance variable
        self.first = first
        self.last = last
    
    # instance class
    def get_detail(self, mark):
        return self.first + " " + self.last + " " + str(mark)

stud = Student("Ram", "Kumar")

print(stud.get_detail(70))

The output

Ram Kumar 70

Class method:

• Class method can be accessed only by the class itself, not to any specific instance object.
• “cls” is the first parameter in the class method when define.
• @classmethod function to define the class method.
• Class method can access or modify the class state.
• Class methods are bound to the class so we should access them using the class name.

class Student:
    #class variable
    percent = 10
    # initialization method
    def __init__(self, first, last, age):
        self.first = first
        self.last = last
        self.age = age

    # instance method
    def mark(self, mark, percent):
        self.mark = mark
        self.percent = percent

    # class method
    @classmethod
    def change_per(cls, percent):
        cls.percent = percent + percent

stud = Student("Ram", "Kumar", 50)
#calling class variable
Student.change_per(50)
stud.mark(100, Student.percent)
print(stud.__dict__)

The output:

{‘first’: ‘Ram’, ‘last’: ‘Kumar’, ‘age’: 50, ‘mark’: 100, ‘percent’: 100}

Static method:

• Static method is a general utility method that performs a task in isolation.
• Static methods have limited use because they don’t have access to the attribute of an object and class attribute.
• @staticmethod to define a static method.
• Static method don’t take an instance or class parameter
• It can’t modify the class or object state.

class Student:
    #class variable
    percent = 10
    # initialization method
    def __init__(self, first, last, age):
        self.first = first
        self.last = last
        self.age = age

    # instance method
    def mark(self, mark, percent):
        self.mark = mark
        self.percent = percent

    # Static method
    @staticmethod
    def get_age(age):
        return age

stud = Student("Ram", "Kumar",Student.get_age(50))
#calling class variable
stud.mark(100, Student.percent)
print(stud.__dict__)

The output

{'first': 'Ram', 'last': 'Kumar', 'age': 50, 'mark': 100, 'percent': 10}

Example 1:

class Student:
    percent = 10
    def __init__(self, first, last, age):
        self.first = first
        self.last = last
        self.age = age

    def mark(self, mark, percent):
        self.mark = mark
        self.percent = percent

    @classmethod
    def change_per(cls, percent):
        cls.percent = percent + percent

    @staticmethod
    def get_age(age):
        return age


stud = Student("Hello", "World", Student.get_age(50))
Student.change_per(20)
stud.mark(100, Student.percent)
print(stud.__dict__)

The output:

{'first': 'Hello', 'last': 'World', 'age': 50, 'mark': 100, 'percent': 40}