Скачать или смотреть Extending Lists in Python: A Guide to Merging Two Lists Every Nth Item

Learn how to merge two lists in Python, inserting all elements of one list into another at specified intervals with practical examples.
---
This video is based on the question https://stackoverflow.com/q/63890485/ asked by the user 'Hellyeah' ( https://stackoverflow.com/u/8271606/ ) and on the answer https://stackoverflow.com/a/63890824/ provided by the user 'Chris' ( https://stackoverflow.com/u/4718350/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How do I extend all elements of a list to another list every Nth item

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Extending Lists in Python: A Guide to Merging Two Lists Every Nth Item

When working with lists in Python, there often arises a need to combine them in particular ways to achieve desired outcomes. One interesting challenge is merging two lists by inserting all elements from one list into another at specified intervals. Understanding how to manipulate lists can greatly enhance your data processing skills in Python. In this post, we'll explore how to achieve this using practical examples.

The Problem Statement

Suppose you have two lists:

l1 with elements ["a", "b"], and

l2 with elements ["j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u"]

Your goal is to create a new list that outputs elements from l2, but with the elements from l1 inserted after every N elements from l2. In this example, we would like to insert l1 after every 3rd element from l2.

Expected Output:

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

The Solution

There are several ways to tackle this problem. One robust approach is to use the more_itertools library, which provides helpful functions that simplify list manipulations.

Step-by-Step Solution Using more_itertools

Install more_itertools: If you don't have this library, you can install it via pip. Open your terminal and execute:

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

Import the library: Start your Python script by importing the necessary module.

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

Define your lists: Set up the lists you will be working with.

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

Merge the lists: Use intersperse to insert l1 into l2 at your desired intervals and collapse to flatten the list.

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

Print the result: Finally, check the output to ensure it meets your expectations.

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

Complete Example Code

Here’s the full code snippet reflecting the steps above:

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

Explanation of the Code

The intersperse function intersperses the elements from the first list (l1) into the second list (l2). The n parameter determines how often to intersperse the elements.

collapse flattens the resulting nested list back into a single list.

Handling Trailing Elements

If you want to avoid having the elements from l1 appended at the end, you can use list slicing to remove the last few elements after merging:

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

Conclusion

This method provides a powerful way to merge lists in a controlled manner in Python. The more_itertools library minimizes the complexity while achieving elegant solutions for list manipulations. Experiment with different N values, and explore how this technique can optimize your workflows in Python. Happy coding!