How to Join Items in a List of Lists by Specific Character Length

Learn how to easily `join` items from lists in Python based on specific character lengths. This guide provides clear examples and Python code snippets.
---
This video is based on the question https://stackoverflow.com/q/72145986/ asked by the user 'perrus' ( https://stackoverflow.com/u/14687951/ ) and on the answer https://stackoverflow.com/a/72146027/ provided by the user 'Cory Kramer' ( https://stackoverflow.com/u/2296458/ ) 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: Join by specific length of character

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.
---
Joining Items in a List of Lists by Specific Character Length

When dealing with data in Python, you often find yourself needing to manipulate and transform lists to meet specific criteria. One common task is to join items from lists within a list based on certain conditions. In this guide, we’ll explore how to join items in a list of lists based on specified lengths: one item must be exactly 6 characters long, and the other must be exactly 4 characters long.

The Problem

Given the following input: a list of lists containing various strings of different lengths, your goal is to combine items from each sublist that meet the specified character length conditions. Here is the structure of the input:

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

Desired Output

For each sublist in the input, the expected output is a new list of lists where the items that meet the specified length conditions are combined as follows:

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

The Solution

To solve this problem, we can use a list comprehension. List comprehensions in Python provide a concise way to create lists and enable us to filter data while performing operations on the list items. Here's how to approach the problem step-by-step:

Step 1: Understand the List Comprehension Structure

A list comprehension consists of the following structure:

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

new_item is what you want to include in the new list.

iterable is the collection you are iterating over.

condition is the criterion to filter items from the iterable.

Step 2: Write the Join Logic

We will combine the strings from each sublist where the lengths match our criteria. Specifically, we will look for a string of length 6 and a string of length 4. The below code demonstrates how to achieve this:

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

Step 3: Breaking Down the Code

i + j: This expression concatenates the two strings that we are interested in joining.

for i, j, *_ in list_of_lists: This iterates over each sublist and assigns the first two items to i and j, while _ captures any further items (which we ignore).

if len(i) == 6 and len(j) == 4: This condition ensures that only those pairs of items that meet the length requirement are included in the concatenation.

Step 4: Final Result

By executing the above code, we obtain the desired output as follows:

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

Conclusion

Using Python’s list comprehension, we can efficiently filter and join items based on specific conditions in a clean and concise way. This method not only simplifies the code but also enhances readability, making it easy for others (and yourself) to understand later. Give this technique a try in your next data manipulation task!