Is self in python same as this?
If you have been programming in Python (object-oriented programming) for some time, then you have definitely come across methods that have Show
Let us first try to understand what this recurring self parameter is. What is self in Python?In object-oriented programming, whenever we define methods for a class, we use
In
this case all the methods, including We know that class is a blueprint for the objects. This blueprint can be used to create multiple numbers of objects. Let's create two different objects from the above class.
The However, since the class is just a blueprint, Why is self explicitly defined everytime?Even when we understand the use of So, why do we need to do this? Let's take a simple example to begin with. We have a
Let us now instantiate this class and find the distance.
In the above example, What Happens Internally?
We can see that the first one is a function and the second one is a method. A peculiar thing about methods (in Python) is that the object itself is passed as the first argument to the corresponding function. In the case of the above example, the method call Generally, when we call a method with some arguments, the corresponding class function is called by placing the method's object before the first argument. So, anything like This
is the reason the first parameter of a function in class must be the object itself. Writing this parameter as Self Can Be AvoidedBy now you are clear that the object (instance) itself is passed along as the first argument, automatically. This implicit behavior can be avoided while making a static method. Consider the following simple example:
Here,
From the above example, we can see that the implicit behavior of passing the object as the first argument was avoided while using a static method. All in all, static methods behave like the plain old functions (Since all the objects of a class share static methods).
Self Is Here To StayThe explicit There is no explicit variable declaration in Python. They spring into action on the first assignment.
The use of In the first example, self.x is an instance attribute whereas x is a local variable. They are not the same and they lie in different namespaces. Many have proposed to make self a keyword in Python, like While this idea seems promising, it is not going to happen. At least not in the near future. The main reason is backward compatibility. Here is a blog from the creator of Python himself explaining why the explicit self has to stay. __init__() is not a constructorOne important conclusion that can be drawn from the information so far is that the A closer inspection will reveal that the first parameter in Technically speaking, a constructor is a method which creates the object itself. In Python, this method is
When Again, like self, cls is just a naming convention. Furthermore, *args and **kwargs are used to take an arbitrary number of arguments during method calls in Python. Some important things to remember when implementing
Let's take a look at an example:
Now, let's now instantiate it.
This example illustrates that In Python, Use __new__ or __init__?You might have seen We can also use One practical use of Suppose we wanted a class
A sample run:
Why does Python use self instead of this?The self is used to represent the instance of the class. With this keyword, you can access the attributes and methods of the class in python. It binds the attributes with the given arguments. The reason why we use self is that Python does not use the '@' syntax to refer to instance attributes.
What is self called in Python?The self parameter is a reference to the current instance of the class, and is used to access variables that belongs to the class.
Is this in CPP same as self in Python?self & this have the same purpose except that self must be received explicitly. Python is a dynamic language. So you can add members to your class. Using self explicitly let you define if you work in the local scope, instance scope or class scope.
Does Python use this?Object-oriented programming
C++ and languages which derive in style from it (such as Java, C#, D, and PHP) also generally use this . Smalltalk and others, such as Object Pascal, Perl, Python, Ruby, Rust, Objective-C, DataFlex and Swift, use self .
|