InstanceandClassVariables.md

Instance and Class Variables

• the variable inside class also called attributes.
• there are two different types of variables appears in classes and object. 1.instance variable 2.class variable

1.instance variable

• instance variable defined inside a constructor init() method of the class.
• Every object has its copy of an instance
• to call an instance variable inside a class self keyword is used.

self.variablename

• instance variables can be accessed outside of class using class object reference or class name

objectname.instancevariablename

Syntax:

class <class name>:
    def __init__(self,variable, var2):
      self.variable=variable
      self.var2=var2

Example:

#class initilization
class Circle():
    #Define constructor with paramter
    def __init__(self,radious,pi):
        #declare instance variables here
        self.radious=radious
        self.pi=pi      #instance variable
    def area(self):
        return self.pi*self.radious**2
        
#create Object of class and pass parameter
circle1=Circle(3,3.14)  #we are sending instance variable

#Call area method using class object
print("Circle Of Area")
print(circle1.area())

Output:

Circle Of Area
28.26

2.class variable

• class variable defined outside of init() methods.
• Here only one copy of the class variable created and it shared with all objects of a class.
• to access class variables inside a class  we need to use class name dot(.) Notation and class variable  classname.variable_name
• The class variable can be accessed outside of class using class name either object reference

objectname.classvariable

Syntax:

class <class name>:
  #class variables
  Var1=value

  def __init__(self,variable, var2):
         #instance variable

Example:

#class initilization
class Circlec():
  
  #declare class variables here
  pi=3.14   
  
  #Define constructor with paramter
  def __init__(self,radious):
      self.radious=radious
  def area(self):
      #Here we called class variable in another method
      return Circlec.pi*self.radious**2 
      
#create Object of class and pass parameter
circlec=Circlec(3)

#Call area method using class object
print(circlec.area())

Output:

28.26