Скачать или смотреть Efficiently Create a List from Iterative Elements in Python

Discover how to dynamically create a list from variables in Python using iteration, perfect for when you have many elements sharing a common naming pattern.
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This video is based on the question https://stackoverflow.com/q/63994369/ asked by the user 'Manolo Dominguez Becerra' ( https://stackoverflow.com/u/4913254/ ) and on the answer https://stackoverflow.com/a/63994479/ provided by the user 'elmo26' ( https://stackoverflow.com/u/12019063/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

Creating lists in Python is simple when you have a small number of variables to work with. However, when you're dealing with hundreds of variables that share common characteristics in their names, it can become quite tedious to create a list manually. In this guide, we’ll explore how you can efficiently create a list from elements using their common naming pattern.

Problem Statement

You might have variables named Test_1, Test_2, and so on, each containing string values. While it's straightforward to create a list with few variables like this:

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However, what if you had a couple of hundred such variables? Manually adding each variable to a list is not practical. This is where Python’s dynamic capabilities come into play, allowing for a more efficient solution.

Solution Breakdown

To accomplish this, we can utilize Python’s built-in locals() function. This function returns a dictionary representation of the current local symbol table, which includes all variable names and their values. We can then filter these variables based on their names.

Step 1: Retrieve Local Variables

First, we will retrieve all local variables using locals():

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

This gives us a dictionary where keys are variable names and values are their assigned values.

Step 2: Filter for Specific Variables

We want to filter out the variables that start with a specific prefix, such as Test_. We can do this using a list comprehension:

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Explanation of the Code

List Comprehension: This allows us to create a new list in a single line of code.

Condition: We check if the variable name starts with "Test_" using the startswith() method.

Result: This creates a list containing all values of the variables that match our condition.

Combined Code Example

Here’s what the complete code looks like:

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

Conclusion

Using the locals() function combined with list comprehension, you can effortlessly create a list of variables that share a common prefix in their names. This method is not only efficient but also scalable, making it extremely useful when handling a large number of variables in Python.

So next time you find yourself with many similarly named variables, remember this technique to streamline your code and improve readability!