Settings

Report a bug

Email:

Subject:

Message:

Share your code

Link:

Embed on your site:

Something went wrong. Please try again later.

Show Hint

The hint to the solution will replace your current work in the editor. Do you want to see the hint?

Show Sample Solution

The sample solution will replace your current work in the editor. Do you want to see it?

Python allows for variables to be used at the instance level or the class level. Those used at the instance level are referred to as instance variables, whereas variables used at the class level are referred to as class variables.

Instance variables

This kind of variable exists when and only when it is explicitly created and added to an object. This can be done during the object's initialization, performed by the __init__ method, or later at any moment of the object's life. Furthermore, any existing property can be removed at any time.

Each object carries its own set of variables – they don't interfere with one another in any way. The word instance suggests that they are closely connected to the objects (which are class instances), not to the classes themselves. To get access to the instance variable, you should address the variable in the following way: objectdotvariable_name.

Let's look at how the instance variable is created and accessed in the code presented below.

class Demo:
    def __init__(self, value):
        self.instance_var = value

d1 = Demo(100)
d2 = Demo(200)

print("d1's instance variable is equal to:", d1.instance_var)
print("d2's instance variable is equal to:", d2.instance_var)

__init__ creates an instance_var variable for the instance. The keyword self is used to indicate that this variable is created coherently and individually for the instance to make it independent from other instances of the same class;
we instantiate the class twice, each time passing a different value to be stored inside the object;
the print instructions prove the fact that instance variable values are kept independently, because the printed values differ.

Instance variables

Code