Troubleshooting Ansible: How to Access Attributes from a Dictionary in Jinja2

Discover the solution to accessing dictionary attributes in Ansible playbooks. Learn why your expected values are returning empty lists and how to correctly reference dictionary keys in Jinja2 templates.
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Troubleshooting Ansible: How to Access Attributes from a Dictionary in Jinja2

As an Ansible user, you might find yourself perplexed when your code doesn't behave as expected. One common issue arises when trying to display specific attributes from a dictionary using Jinja2. In this post, we’ll dive into a use case where a user encounters an empty list, and we’ll walk through the solution step-by-step.

The Problem Explained

A user running Ansible 2.9.27 on Red Hat Linux 7.9 was trying to access attributes from a dictionary called found_service_accounts, which contained information about service account details. The problem occurred specifically with the following code:

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

The output showed the expected home details for svclinux, but when the user attempted to filter with selectattr, they got an empty list. This was confusing, as they expected to see the path attribute.

Understanding the Issue

The crux of the issue lies in how dictionaries work in Jinja2 and Ansible. The found_service_accounts['svclinux']['home'] is a dictionary itself, not a list. Thus, when the user attempted to use selectattr, it did not return the desired results. Here's why:

Dictionaries store key-value pairs, while lists are ordered collections of items.

When iterating over a dictionary, Jinja2 will return the keys instead of the values, leading the selectattr to look for an attribute path within the keys (["owner", "path", "group", "permissions"]), which does not exist as a key in this context.

The Solution

To fix the issue, you simply need to directly access the path attribute within the dictionary without using selectattr. Here’s the corrected code snippet:

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

This adjustment retrieves the value corresponding to the path key directly, effectively fixing the problem.

Summary

To sum up, when working with dictionaries in Ansible and Jinja2:

Understand the data structure: Know when you are working with a dictionary versus a list.

Directly access dictionary keys: Use found_service_accounts['svclinux']['home']['path'] instead of trying to filter attributes with selectattr.

By following these guidelines, you'll avoid similar pitfalls in your Ansible playbooks and save yourself valuable debugging time. Happy coding!