Скачать или смотреть Looping Over a Multi-Level List in Ansible: Your Complete Guide

Learn how to effectively loop over a multi-level list in Ansible using Jinja2 to achieve customized outputs.
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Looping Over a Multi-Level List in Ansible: Your Complete Guide

As an Ansible user, you might encounter situations where you're dealing with complex data structures, such as multi-level lists. One common challenge is the need to format these lists into a more readable or user-friendly output. This post addresses a specific question: how do you loop over a multi-level list in Ansible to produce a desired output format?

Understanding the Problem

Suppose you have the following multi-level list (YAML structure) defined in Ansible:

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

With this structure, you may want to output the information in a more readable way, for example:

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

However, your initial attempt with a Jinja2 template only provides the following output:

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

Clearly, we need a better approach using Jinja2's powerful templating capabilities to achieve the desired format.

The Solution

To obtain the formatted output, we can make slight modifications to our original Jinja2 loop. Below is a refined approach that allows us to extract the keys and values properly and concatenate them as needed.

Step-by-Step Implementation

Start with a Debug Task: This task will help us demonstrate the output formatting.

Modify the Jinja2 Loop: Change the way we iterate through the elements list to directly access both keys and their associated values.

Here’s how the modified template looks:

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

Breaking Down the Code

Looping Through Elements: The {% for level1 in elements %} loop allows us to access each dictionary within the list.

Extracting Keys: Using {{ level1.keys()|first }} extracts the first key from each dictionary, which corresponds to aaaa and bbbb in our example.

Getting Values: The nested loop {%- for v in level1.values()|first %} retrieves all values associated with that key and formats them appropriately.

Output the Message: The final output concatenates results into a single, readable line.

Resulting Output

When you run this task, the output generated will be exactly what you wanted:

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

Conclusion

Handling multi-level lists in Ansible can initially be confusing, but with the correct Jinja2 templating logic, you can efficiently format and display your data. By following the steps outlined in this guide, you’ll be able to customize your output to suit various needs in your Ansible playbooks.

Feel free to experiment with this method in your own projects and see how it can streamline data presentation in your automation scripts!