Скачать или смотреть How to Group Elements in a List of Lists Based on Another List of Lists in Python

Discover how to effectively reorder elements in one list of lists based on the structures of another while maintaining specific rules in Python.
---
This video is based on the question https://stackoverflow.com/q/75778998/ asked by the user 'donmoy' ( https://stackoverflow.com/u/8327752/ ) and on the answer https://stackoverflow.com/a/75779331/ provided by the user 'Alain T.' ( https://stackoverflow.com/u/5237560/ ) 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: Group elements in list of lists based on elements in another list of lists

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.
---
Introduction

When working with data in Python, particularly with lists of lists, you may find yourself needing to reorder one list based on the structure of another. This can be especially challenging if certain groups of elements must not be broken up during the reordering process. In this guide, we'll tackle a specific problem involving two lists of lists, A and B, and devise a solution to reorder elements in B so that its sublists correspond to the groupings found in A.

The Problem at Hand

We are given two lists of lists:

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

The goal is to reorder the elements in B such that:

Each sublist in B contains the same groups of elements as the sublists in A.

The length of B remains unchanged.

Sublists in B should remain unchanged if:

They contain all their elements that exist within a group in A.

They consist exclusively of single-element sublists in A.

For example, a possible output for B could look like:

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

Solution Explanation

To solve this problem, we can break down the solution into several organized steps. We will develop a Python function that leverages recursion and set manipulation to efficiently reorder B.

Step 1: Define the Combine Function

The first step is to write a recursive function that combines the elements of A into the structure of B:

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

This function will create all possible combinations of sublists from A while respecting the count (length) derived from B.

Step 2: Identify Fixed Groups

Since we want to preserve certain groups, we need to identify which sublists from A and B cannot be altered. We can do this using sets:

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

Step 3: Implementation and Testing

Now that we have our combining function, we can apply it to our initial lists A and B:

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

This will produce:

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

Additional Considerations

While the solution provided works for the stated problem, there are additional considerations:

What should happen if there are more fixed groups than available slots in B?

Handling overlapping groups between A and B.

Managing larger groups or combinations that have more than two elements.

These factors can add complexity and merit further exploration to refine the solution based on specific needs.

Conclusion

Reordering elements in a list of lists based on another can be a challenging task in Python, especially when certain groups need to remain intact. By leveraging recursion and set manipulation, as we've demonstrated through the example, you can create a robust solution to this problem. Keep in mind the additional edge cases that may arise and adjust your approach as necessary.

With this knowledge, you will be better equipped to handle similar data manipulation tasks in your Python programming endeavors.