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self in Python class

  • Difficulty Level : Easy
  • Last Updated : 05 Jul, 2021

self represents the instance of the class. By using the “self” keyword we can access the attributes and methods of the class in python. It binds the attributes with the given arguments.
The reason you need to use self. is because Python does not use the @ syntax to refer to instance attributes. Python decided to do methods in a way that makes the instance to which the method belongs be passed automatically, but not received automatically: the first parameter of methods is the instance the method is called on.

In more clear way you can say that SELF has following Characteristic-

Self is always pointing to Current Object.

Python3




#it is clearly seen that self and obj is referring to the same object
 
class check:
    def __init__(self):
        print("Address of self = ",id(self))
 
obj = check()
print("Address of class object = ",id(obj))
 
# this code is Contributed by Samyak Jain
Output
Address of self =  140124194801032
Address of class object =  140124194801032

Another Example of Using SELF:



Python3




# Write Python3 code here
 
class car():
     
    # init method or constructor
    def __init__(self, model, color):
        self.model = model
        self.color = color
         
    def show(self):
        print("Model is", self.model )
        print("color is", self.color )
         
# both objects have different self which
# contain their attributes
audi = car("audi a4", "blue")
ferrari = car("ferrari 488", "green")
 
audi.show()     # same output as car.show(audi)
ferrari.show()  # same output as car.show(ferrari)
 
# Behind the scene, in every instance method
# call, python sends the instances also with
# that method call like car.show(audi)
Output
Model is audi a4
color is blue
Model is ferrari 488
color is green

Self is the first argument to be passed in Constructor and Instance Method.

Self must be provided as a First parameter to the Instance method and constructor. If you don’t provide it, it will cause an error.

Python3




# Self is always required as the first argument
class check:
    def __init__():
        print("This is Constructor")
 
object = check()
print("Worked fine")
 
 
# Following Error is produced if Self is not passed as an argument
Traceback (most recent call last):
  File "/home/c736b5fad311dd1eb3cd2e280260e7dd.py", line 6, in <module>
    object = check()
TypeError: __init__() takes 0 positional arguments but 1 was given
   
   
  # this code is Contributed by Samyak Jain

Self is a convention and not a Python keyword .

self is parameter in Instance Method and user can use another parameter name in place of it. But it is advisable to use self because it increases the readability of code, and it is also a good programming practice.

Python3




# Write Python3 code here
 
class this_is_class:
    def __init__(in_place_of_self):
        print("we have used another "
        "parameter name in place of self")
         
object = this_is_class()
Output
we have used another parameter name in place of self

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