self and __init__ in Object oriented Python

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Let's first observe below Python code 

# Python code for planet name, radius and it's distance from the star.
class Planet:
             def __init__ (self, name, radius, distance):                  # constructor
                     self.name = name
                     self.radius= radius
                     self.distance=distance
             def system (self):
                     print ("Name of the planet: ", self.name)
                     print ("Radius of the planet: ", self.radius)
                     print ("Distance from the star: ", self.distamce)
p1 = Planet (Jupiter, 69911, 757.4)
# declaration of object 1
p2 = Planet (Neptune, 24,622, 4.4756)
# declaration of object 2

print ("Name of the planet: ",p1.name)
print ("Radius of the planet: ",p1.radius)
print ("Distance from the star: ",p1.distance)

#******************************************

p1.system (Jupiter, 69911, 757.4)
# calling the system method 

p2.system (Neptune, 24622, 4.4756)
# calling the system method 

In above code 
self is the reference variable always pointing to the current object 
self is not a Python keyword it is just a convention 
self is use to access instance variable inside the class 

Inside self.name, self.radius, self.distance is used to access the instance variables

Outside the class p1.name, p1.radius, p2.distance is used to access the instance variables 

In java "this" keyword is used to access instance variables 

__init__ is the special type of method called constructor 
It is used for declaration and initialisation of instance variables 
__init__ means initialisation

Instance variables are those variables which are change from object to object 

In above code "name", "radius", "distance" are the instance variables 

for example in  p1 object planet name is  Jupiter, radius is 69911 and distance is 757.4 
whereas in p2 object planet name is Neptune, radius is 24622 and distance is
4.4756 

you can see clearly that the value of instance variables is different in both objects p1 and p2 

Thank you 
Author YASH SHRIMALI
Technology Practitioner

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