Скачать или смотреть How to Extract Integers from a Nested List in Python with str.isdigit()

Learn how to convert strings to integers in a nested list using Python's built-in methods, making your programming experience seamless!
---
This video is based on the question https://stackoverflow.com/q/66997738/ asked by the user 'Trojan666' ( https://stackoverflow.com/u/14466246/ ) and on the answer https://stackoverflow.com/a/67000117/ provided by the user 'sahasrara62' ( https://stackoverflow.com/u/5086255/ ) 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: Take integer only from a nested list and apply function to it

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.
---
Extracting Integers from a Nested List in Python

Dealing with nested lists can be quite tricky, especially when you need to handle different data types within them. This is a common challenge for beginners in Python programming. In this guide, we'll tackle a specific problem: How do we extract integers from a nested list that contains both strings of digits and characters?

The Problem

Suppose you have a nested list like this:

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

This list contains sub-lists where each element is a string. Some strings represent digits (like '1', '2', '0', etc.), while others are characters ('a', 'b', etc.). Your goal is to convert the strings of digits into actual integers, while keeping the characters as they are. The desired output would look like this:

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

The Solution

To solve this problem, we'll use Python's capabilities to check if a string represents an integer and then convert it accordingly. There are two effective approaches to achieve this, as outlined below.

Approach 1: Using map() and List Comprehension

One of the most concise methods employs the map() function combined with a list comprehension. This approach allows us to iterate over each sub-list and apply a function to each element in one line. Here’s how you can do it:

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

Explanation:

map() Function: This function applies the provided function to all items in the input list.

lambda y: This creates an anonymous function that processes each sub-list.

List Comprehension: For each element x, it checks if x.isdigit(). If it does, it converts x to an integer; otherwise, it just keeps x as it is.

Approach 2: Using a For Loop with Error Handling

If you prefer a more traditional approach, you can use nested for loops along with error handling to catch any conversion exceptions that arise. Here’s how you can do it step-by-step:

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

Explanation:

Outer Loop: Iterates through each sub-list in lists.

Inner Loop: Iterates through each item in the current sub-list.

try-except Block: Attempts to convert each string j to an integer. If it fails (for non-digit strings), it catches the ValueError and assigns val to j instead.

Temporary List: Each processed element is appended to a temporary list tmp, which is then appended to the final list2 variable.

Conclusion

Both methods are efficient, but which one you choose depends on your personal coding style. Using map() and list comprehensions can lead to more readable and concise code, while the for-loop method gives you finer control and flexibility through error handling.

With these approaches, you can now confidently extract integers from nested lists in Python! Keep practicing, and you'll find handling data structures becomes easier over time. Happy coding!