Instance,Static and Class Methods in Python

                         

Instance Method

They are most widely used methods. Instance method receives the instance of the class as the first argument, which by convention is called self.

class Student:

  def __init__(self,name):

    self.name = name

  def printinfo(self):

    self.city = 'delhi'

    print('my name is {} and from {}'.format(self.name,self.city))

  def printcity(self):

    print('my city is ', self.city)

stud1 = Student('tom')

stud1.printinfo()

Output:

my name is tom and from delhi

class method

Class methods don't need self as an argument, but they do need a parameter called cls. 

This stands for class, and like self, gets automatically passed in by Python.

Class methods are created using the @classmethod decorator.

class Student:

  Studentcount = 10

  @classmethod

  def printcount(cls):

    print('class is having {} number of students'.format(cls.Studentcount))

Student.printcount()

Output:class is having 10 number of students

class Student:

  Studentcount = 0

  def __init__(self):

    Student.Studentcount += 1

  @classmethod

  def printcount(cls):

    print('class is having {} number of students'.format(cls.Studentcount))

stud1 = Student()

stud2 = Student()

Student.printcount()

class is having 2 number of students

Stud1.printcount() #using instance and calling class method

class is having 2 number of students

static method 

This type of method takes neither a self nor a cls parameter (but of course it’s free to accept an arbitrary number of other parameters).

Therefore a static method can neither modify object state nor class state. Static methods are restricted in what data they can access

class Student:

  

  @staticmethod

  def printname(x):

    print('student name is {}{}'.format(x))

  

  @staticmethod

  def printage(x):

    print('student age is {}{}'.format(x))

Student.printname('sam')

student name is Mr.sam