This tutorial will explain the purpose and use of the
self keyword in Python. In object-oriented programming, we have classes, and each class has various attributes and methods. Whenever an object or instance of a class is created, the constructor (
__init__() method in Python) is called to initialize the instance’s attributes.
While creating an instance of a class, we need to differentiate or specify the instance attributes from the arguments and other variables. And that’s where we need the
self keyword to specify that we are passing the value to the instance attributes and not to the local variable or argument with the same name.
Suppose, for a class
car we pass argument
color to the
__init__() method to initialize the
color attribute of the
car class, we will specify the
color attribute of the instance as
self.color, which shows that the class
car has an attribute
color and we assign the value to that attribute.
Similarly, we can also call the class’s instance methods using the
self keyword like
self.start() method of the
car class. So in short we can say that the
self keyword allows the user to specify and access the attributes and methods of an instance of the class.
Use and Example Codes of the
self Keyword in Python
Now, let us look into how the
self keyword is used in Python to specify an instance’s methods and attributes through the example code.
The first example code given below demonstrates how the
self keyword is used in the
__init__() method to initialize the attributes of the instance being initialized. We do not need to declare or create variables before initializing or assigning values to them so that we can initialize the instance attributes in the following way:
class car: def __init__(self, model, color): self.model = model self.color = color mycar = car('model XYZ','red') print(mycar.model) print(mycar.color)
model XYZ red
As can be seen above, the
__init__() method is called automatically on creating a new instance of the class, and its attributes get initialized. The
self needs to be the method’s parameter to access the instances’ methods and attributes.
The below example code demonstrates how to use the
self keyword to call the instance/class methods within other class methods in Python.
class car: def __init__(self, model, color): self.model = model self.color = color self.start() def start(self): print(self.model + ", has started!") mycar = car('model XYZ','red')
model XYZ, has started!
As in the above example code, we can call class methods using the
self keyword and access the attributes in any class method by passing the instance of the class as