Sorting a List of Strings by Custom Key in Python: An Easy Approach to Optimize Your Code

Discover how to efficiently sort a list of two-character strings in Python by using a custom key. Learn the ultimate strategy to optimize your code with this easy-to-follow guide!
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Sorting a List of Strings by Custom Key in Python

Sorting is an essential operation in programming, and in Python, you can perform sorting with great flexibility. However, sometimes the sorting criteria may not be straightforward. This guide addresses a common issue faced by many developers: how to sort a list of two-character strings based on a specific order, particularly when dealing with alphanumeric and numeric-only strings.

The Problem

In a recent live coding interview, a candidate was presented with the challenge of sorting a list of two-character strings. The task required them to:

Sort strings containing both alpha and numeric characters first.

Follow this by sorting strings with numeric characters second.

Given a list like:

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

The expected output after sorting should be:

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

Initial Approach

The initial solution utilized a manual approach where the strings were divided into two lists: one for alphanumeric strings and the other for purely numeric ones. Here's how it looked:

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

This code worked well, but it involved extra steps like creating separate lists and merging them back together, which could be a performance bottleneck.

The Efficient Solution

While the previous method worked, there's a more efficient way to achieve the same result using the built-in sorted() function and a custom key. This approach is not only concise but also optimizes resource usage by eliminating unnecessary list manipulations.

How to Sort with a Custom Key

You can use a lambda function to define a sorting key that meets the specified criteria. Here's the clean and efficient solution:

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

Explanation of the Key:

Final Output

Carrying out the above sorting will yield the same expected result:

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

Conclusion

By utilizing a custom key in Python’s sorting functions, you can significantly enhance the efficiency of your sorting operations. Not only does this method produce cleaner code, but it also reduces computational overhead by performing sort operations without extra list copying.

In summary, when confronted with sorting tasks involving mixed data types:

Use sorted() with a custom key.

Keep it simple and readable.

Adopting these practices can streamline your coding process, making you a more efficient programmer.