Solving the IndexError: list index out of range in Python3 Explained

Discover how to fix the common `IndexError: list index out of range` in Python3 when finding the largest product of adjacent elements in an array.
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Understanding the IndexError: list index out of range in Python3

Encountering an IndexError in Python can be frustrating, especially if you are not sure what caused it. If you've been working with arrays and came across an error stating "IndexError: list index out of range," you're not alone. This guide will help you understand the root of this error and how to resolve it effectively, particularly when trying to find the largest product of adjacent elements in an array.

The Problem at Hand

The task is to find a pair of adjacent elements in an array of integers that has the largest product and return that product. Let's take a closer look at your initial code and see how it generates an IndexError.

Your Initial Code

You proposed the following function:

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The Cause of the Error

The IndexError occurs due to this line:

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When your loop iterates to the last element of the array, it tries to access inputArray[i + 1], which does not exist since i will be equal to length_of_array - 1. This is why you receive the error message: it’s trying to access an index that exceeds the bounds of the array.

The Solution

Fixing Your Code

To prevent the IndexError, you should adjust the loop so that it stops one iteration sooner. You can do this by modifying the range in your for loop as follows:

[[See Video to Reveal this Text or Code Snippet]]

Using zip for an Easier Solution

A more Pythonic way to solve this problem is to use the zip() function, which allows you to combine elements from two lists effectively. Here’s how you can simplify the solution:

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With this approach, you're using zip() to create pairs of adjacent elements from the input array and then calculating the maximum product. This avoids the pitfalls of index-based access entirely and results in cleaner code.

Conclusion

In summary, an IndexError: list index out of range commonly occurs when attempting to access an array index that doesn't exist. By properly adjusting the range of your loops and leveraging Python’s built-in functions like zip(), you can efficiently find the largest product of adjacent elements in an array without running into errors. If you ever face a similar issue, refer back to this guide to troubleshoot effectively!

Happy coding!