Skip to content

Check is instance

Quality Score

Overall Score: 9.5/10 ⭐ Outstanding

  • Technical Accuracy: 33/35
  • Code Quality: 25/25
  • Educational Value: 23/25
  • Documentation: 15/15

Last reviewed: June 22, 2026

Python is not a strong-typed language. This mean, that a variable can be assigned to any type, even if previously it was assigned to another type.If developers doesn't take care of this, it can lead to bugs and unexpected behavior.

Python supports type hints in the code, but it is not enforced. Python provides a built-in method called isinstance, that can be used to check if a variable is of a certain type. It requires two arguments, the variable to be checked and the type or tuple of types to be checked against. It returns True if the variable is of the specified type, and False

src.beginner.check_is_instance

Module to check if an instance is of a given type.

This module contains a function to check if an instance is of a given type.

src.beginner.check_is_instance.is_instance(instance, instance_type)

Check if instance is of the type provided.

Parameters:

Name Type Description Default
instance object

any kind of object.

 required
instance_type class or tuple

expected instance type for instance.

 required

Returns:

Name Type Description
bool bool

true if instance is the one expected, false otherwise.
Source code in src/beginner/check_is_instance/check_is_instance.py 
 8
 9
10
11
12
13
14
15
16
17
18
def is_instance(instance, instance_type) -> bool:
    """Check if instance is of the type provided.

    Parameters:
        instance (object): any kind of object.
        instance_type (class or tuple): expected instance type for instance.

    Returns:
        bool: true if instance is the one expected, false otherwise.
    """
    return isinstance(instance, instance_type)

This is useful because depending on the type, they offer different methods and attributes. You can do len of a string, but not of an integer.

Type

Another built-int method in python is type, that returns the type of variable. It is not as flexible as isinstance because it only checks for the exact type, and not for the subclasses (important when doing inheritance).

src.beginner.check_is_instance

Module to check if an instance is of a given type.

This module contains a function to check if an instance is of a given type.

Common pitfalls

There are some common pitfalls when using isinstance. bool is a subclass of int, so if you check if a variable is an instance of int, it will return True for a boolean variable. This can lead to unexpected behavior if you are not aware of this.