Скачать или смотреть How to Print a 2D List in Python: Rows Reversed and Columns Left to Right

Learn how to properly display a 2D list in Python with rows displayed from bottom to top and columns from left to right. Effective solutions and coding tips included!
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This video is based on the question https://stackoverflow.com/q/63851472/ asked by the user 'Joe Deer' ( https://stackoverflow.com/u/14251090/ ) and on the answer https://stackoverflow.com/a/63983191/ provided by the user 'Hamza' ( https://stackoverflow.com/u/7212929/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Print a 2D List in Python: Rows Reversed and Columns Left to Right

If you're programming in Python and working with 2D lists (or grids), you might face the challenge of formatting your output properly. Specifically, you may need to display your data with the rows printed from the bottom up, and the columns shown from left to right. This post explores how to achieve this with effective coding strategies.

Understanding the Challenge

Imagine you have a 3x3 grid represented as a 2D list as shown below:

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

The goal is to print this grid such that the rows appear from the bottom to the top. In our example, the output should look like this:

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

However, if your current code outputs:

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

Then there's room for improvement. Let's dive into the solution step-by-step.

Step-by-Step Solution

1. Understanding the Current Code

First, let’s take a look at the code provided and the issue at hand. Here’s a general structure of the function that was being used:

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

2. Issues with the Current Code

From the code above, we can see:

The outer loop correctly iterates through the rows in reverse order.

The inner loop iterates through each column but prints each value without properly formatting them in the desired order.

3. A More Efficient Approach Using Numpy

Instead of manually iterating through the lists, we can use the powerful Numpy library which simplifies array manipulations significantly. By converting the list to a Numpy array, we can quickly transpose rows and columns—reversing the rows in one convenient step.

Here's how you can use Numpy:

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

In this code:

We convert the list to a Numpy array with np.array(lst).

The .transpose() method flips rows and columns.

The slicing [::-1] reverses the rows.

4. Example Output

After running the code above, you will get the output:

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

Final Thoughts

Using Numpy can save you a significant amount of time and reduce potential mistakes when dealing with matrices or 2D lists in Python. This approach not only simplifies your code but also enhances readability and efficiency.

Whether you're building games, data visualizations, or simple displays, mastering the manipulation of 2D lists can be highly beneficial in your Python journey. Happy coding!