Resolve "List Object Has No Attribute Length" in Ansible

Get expert tips on fixing "list object has no attribute length" in Ansible by using Jinja2 filters to accurately measure list lengths in playbooks.

The error message list object has no attribute length typically occurs in Ansible when attempting to use the attribute length on a list. In Ansible, the Jinja2 templating language is used, and lists don’t have a length attribute. Instead, you should use the length filter to get the length of a list.

Here's how to resolve this issue:

Problem

You may be trying to get the length of a list like this:

``yaml


name: Display list length
  ansible.builtin.debug:
    msg: "{{ my_list.length }}"

This will cause an error because lists in Jinja2 don't have a length attribute.



Solution

Instead, use the length filter:

`yaml


name: Display list length
  ansible.builtin.debug:
    msg: "{{ my_list | length }}"



Example

Suppose my_list is defined as follows:

`yaml


my_list:
  - item1
  - item2
  - item3

Then, to get the length of my_list, you would use:

`yaml


name: Display list length
  ansible.builtin.debug:
    msg: "The length of my_list is {{ my_list | length }}"



Explanation

my_list | length applies the length filter to my_list`, which will return the number of elements in the list.

This approach is compatible with Jinja2, which is the templating system Ansible uses.

Additional Tip

If you encounter other similar issues with attributes, remember to check if a Jinja2 filter might solve it, as Ansible commonly leverages filters for list and dictionary operations.