issubclass() Built-in Function

Python - issubclass()

Python issubclass() built-in function is used to check if an object is an instance of specified class.

In this tutorial, we will learn the syntax and usage of isinstance() built-in function with examples.

Syntax

The syntax of isinstance() function is

isinstance(object, classinfo)

where

Parameter	Mandatory/ Optional	Description
object	Optional	A function for getting the attribute value.
classinfo	Optional	A function for setting the attribute value.

Examples

1. Check if given object is an instance of specific class

In the following program, we define two classes: Person and Student. We define Student class such that it is a sub class of Person class. And, we programmatically check that using issubclass() built-in function.

Python Program

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

class Student(Person):
    marks=0
    def printDetails(self):
        print(f"Name: {self.name}\nAge: {self.age}\nMarks: {self.marks}")
        
if issubclass(Student, Person):
    print(f"Student is a sub class of Person.")
else:
    print(f"Student is not a sub class of Person.")

Output

Student is a sub class of Person.

2. Negative Scenario

In the following program, we consider the same two classes from the above program. And we check if Person class is a subclass of list built-in class, or not. Since, we know that is not the case, issubclass() must return False, and else-block must execute.

Python Program

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

class Student(Person):
    marks=0
    def printDetails(self):
        print(f"Name: {self.name}\nAge: {self.age}\nMarks: {self.marks}")

if issubclass(Person, list):
    print(f"Person is a sub class of list class.")
else:
    print(f"Person is not a sub class of list class.")

Output

Person is not a sub class of list class.

Summary

In this Built-in Functions tutorial, we learned the syntax of the issubclass() built-in function, and how to use this function to check if given class is a sub class of other specified class.