Скачать или смотреть How to Re-order a List Based on Another One in Python

Learn how to effectively sort an unordered list by using a reference from another list in Python. This guide provides step-by-step instructions and best practices!
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How to Re-order a List Based on Another One in Python

Sorting lists is a common task in programming, and Python provides powerful ways to manipulate lists efficiently. But what happens when you have an unordered list and you want to sort it based on the order of elements in another ordered list? Let's dive into how you can do this in Python.

The Problem

Imagine you have two lists containing the same items, but the order of items in the second list (the unordered list) is mixed up. Your goal is to rearrange the unordered list to match the order of corresponding items in the first list (the ordered list). For example:

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

You want the unordered_list to change to:

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

The Solution

Using the sort() Method with a Key Function

To achieve this, we can use the sort() method with a custom key function. Specifically, we'll use the index of the items from the ordered_list as the key for sorting the unordered_list. This way, Python knows how to arrange the items based on the positions defined in the ordered_list.

Here’s how you can implement this solution step-by-step:

Define your ordered and unordered lists: Start by creating both lists as shown below.

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

Sort using a lambda function: Use the sort() function and provide a lambda function as the key. This lambda will retrieve the index of each item from the ordered_list to ensure they are sorted correctly.

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

Print the sorted list: After sorting, you can print the reordered unordered_list.

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

Example Implementation

Putting everything together, here is the complete code snippet:

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

Output

The output of the above code will be:

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

Final Thoughts

Sorting lists based on another list's order might seem daunting at first, but with Python’s built-in methods, it can be done efficiently and effectively. Using the index method allows you to achieve this with minimal code, making it both elegant and functional.

Whether you are dealing with a shorter list like the example or a much longer dataset, this solution remains scalable. Now you're ready to handle list reordering in Python with confidence!