Different ways to access Instance Variable in Python

The Instance variables are generally used to represent the state or attributes of an object. Each instance of a class can have its own set of instance variables, which can store unique values. An instance variable is defined within the methods of a class and is accessible throughout the instance's lifespan.

Accessing the instance variable in python

The flexibility that comes with usage of instance variables allows each instance to maintain its own set of variables, enabling customized behaviour and data storage for different objects. Thus, accessing instance variables in python is a useful step.There are different ways to access the instance variable in python, let's see them one by one.

Using the dot notation

The Instance variables can be accessed using the dot notation along with the instance name. This is the easy and simple way to access the instance variable. Following is the syntax for using the dot notation.

instance.variable_name

Where,

• instance is the instance.

• variable_name is the name of the variable.

• represents the dot notation.

Example

In this example, we will access the instance variable from the user defined class by using the dot notation then the instance variable is returned as the output.

class sample_class:
   def __init__(self, variable):
      self.variable = variable

instance = sample_class("Welcome to Tutorialspoint, Have a happy learning!")
print(instance.variable)

Output

Following is the output of accessing the instance variable using the dot notation.

Welcome to Tutorialspoint, Have a happy learning!

Using the self keyword

In a class the self keyword is the reference of the instance. The Instance variables in the class can be accessed by using the self.variable_name. Following is the syntax for using the self keyword to access the instance variable.

self.variable_name

Example

If we want to access the instance variable from the defined class, we can use the self keyword.

class sample:
   def __init__(self, variable):
      self.variable = variable

   def print_variable(self):
      print(self.variable)

instance = sample("Welcome to Tutorialspoint, Have a happy learning!")
instance.print_variable()

Output

Welcome to Tutorialspoint, Have a happy learning!

Using the dict attribute

In every instance in Python language, a dictionary named __dict__ is present, it contains all the instance variables. So, we can access an instance variable with the help of __dict__ attribute. The following is the syntax for using the dict attribute.

instance.__dict__[variable_name]

Example

Here in this example, we will use the __dict__ attribute to get the instance variable of the class.

class sample:
   def __init__(self, variable):
      self.variable = variable
instance = sample("Python is one of the popular programming languages")
print(instance.__dict__['variable'])

Output

Python is one of the popular programming languages

Using the getattr() function

Python provides a built−in function namely getattr() that takes two arguments; an object and a string. This function returns the value of the specified attribute within the object. Following is the syntax for using the getattr() function.

getattr(instance, 'variable_name')

Example

If we want to get the instance variable from the user defined class we need to pass the instance and the variable name to the getattr() function.

class sampe_class:
   def __init__(self, variable):
      self.variable = variable

instance = sampe_class("Hello, Python is one of the popular programming languages!")
print(getattr(instance, 'variable'))

Output

Hello, Python is one of the popular programming languages!

Using the hasattr() function

The hasattr() function is as same as the getattr() function but the only difference is the hasattr() returns the Boolean values True or False. If the variable is present in the class, then output will be returned as True otherwise returned as False.

Syntax

The following is the syntax for using the getattr() function.

hasattr(instance, 'variable_name')

Example

Following example demonstrates the hasattr() function to get the instance variable.

class sampe_class:
   def __init__(self, variable):
      self.variable = variable

instance = sampe_class("Hello, Python is one of the popular programming languages!")
print(hasattr(instance, 'variable'))

Output

True