Скачать или смотреть How to Sort a List of Lists by Number of Elements in Python

Discover how to sort a nested list in Python based on the number of elements in its inner lists for better organization and data processing.
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Introduction

Sorting data can often be a complex task, especially when you're dealing with nested lists in Python. A common scenario is needing to order these lists based on certain criteria. In this guide, we’ll explore a specific problem: How to order a list of lists based on the number of elements within the inner lists.

Let’s dive into a clear example to understand the problem before we explore the solution.

Problem Statement

Consider the following list of lists:

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

Your goal is to sort this list in descending order based on the number of elements in the first inner list of each item. An important note here is that if two items contain the same number of elements, their order relative to each other doesn't matter.

For example, you want to achieve the following output:

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

Solution

To solve this sorting challenge, Python provides an efficient way to sort data using the sorted() function in combination with a custom sorting key. Let’s break down how to implement this step by step.

Step 1: Understanding the Key Function

The key to sorting the list lies in using a lambda function that retrieves the length of the first inner list of each item. In our example, for the first element [[5, 4, 3, 2], [6, 7, 8, 9]], the first inner list is [5, 4, 3, 2], which has 4 elements.

Step 2: Using the sorted() Function

The sorted() function can be used to sort the list based on our custom key. Here is the code to achieve the desired sorting:

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

key=lambda i: len(i[0]): This part of the code tells Python to use the length of the first inner list of each element i as the basis for sorting.

reverse=True: This parameter sorts the list in descending order.

Step 3: Complete Code Example

Putting it all together, here is the complete code to sort your list:

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

Expected Output

After running the code, you will get the output sorted as follows:

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

Conclusion

Sorting a list of lists in Python based on the number of elements in their inner lists is straightforward with the sorted() function and a custom key. By following the steps outlined in this post, you can efficiently manage and organize your data.

If you have more questions or need further examples, feel free to reach out. Happy coding!