LookupError

In Python, LookupError is a built-in exception that serves as the base class for exceptions raised when a key or index used on a mapping or sequence is invalid.

This exception isn’t meant to be directly raised in your code. Instead, it provides a foundation for more specific lookup-related exceptions, such as IndexError and KeyError.

As a developer, you should use LookupError when you want to catch all exceptions related to invalid lookups in mappings or sequences, allowing you to handle them in a unified way.

LookupError Can Be Used When

  • Catching all lookup-related exceptions, such as IndexError and KeyError, in a single try … except block
  • Handling errors when accessing elements in lists, tuples, or dictionaries
  • Creating custom exceptions that need to indicate lookup failures by subclassing LookupError
An Introduction to Python Exceptions

Tutorial

Python Exceptions: An Introduction

In this beginner tutorial, you'll learn what exceptions are good for in Python. You'll see how to raise exceptions and how to handle them with try ... except blocks.

basics python

For additional information on related topics, take a look at the following resources:

By Leodanis Pozo Ramos • Updated May 22, 2025
Python’s Built-in Exceptions Share Feedback