Use instance method and class method properly

This time, I will write about how to use instance methods and class methods properly.

Instance method

Use when you want to control the behavior for each instance

Cannot be called without instantiating
Can be called by instance name.method name
Use self as the first argument

Class method

Used to control common behavior throughout the class

Methods can be called without instantiation
Can be called by class name.method name
Define by adding @ classmethod at the top of the method
Use cls as the first argument of the class method

How to use instance method and class method in school as an example

`school`


class Class:
    #Number of students enrolled in the entire school
    all_students_count = 0

    def __init__(self, teacher_name, grade, group):
        self.teachername = teacher_name
        self.grade = grade
        self.group = group
        self.roster=[]

    def enter(self, name):
        #Instance method
        self.roster.append(name)
        Class.all_students_count +=1

    @classmethod
    def reset_students_count(cls, reset):
        #Class method
        cls.all_students_count = reset

#Record enrollment in 2nd grade and 3rd class with instance method
cl_23 = Class("Yamanaka", 2, 3)
cl_23.enter("Hirasawa")
cl_23.enter("Akiyama")
cl_23.enter("Tainaka")
cl_23.enter("Kotobuki")
cl_23.enter("Manabe")

print("List of enrollees in 2nd grade and 3rd class" , cl_23.roster)
print(cl_23.all_students_count)
#output:List of enrollees in 2nd grade and 3rd class['Hirasawa', 'Akiyama', 'Tainaka', 'Kotobuki', 'Manabe'], 5

#Record one set of enrollees per year with instance method
cl_11 = Class("Toyota", 1, 1)
cl_11.enter("Kaneko")
cl_11.enter("Sato")
cl_11.enter("Shimizu")

print("List of enrollees per year" , cl_11.roster)
print(cl_11.all_students_count)
#output:List of enrollees per year['Kaneko', 'Sato', 'Shimizu'], 8

#Reset all enrollments with class method
Class.reset_students_count(0)
print(cl_11.all_students_count)
#output:0