Resolve "List Object Has No Attribute Length" in Ansible

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:

- 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:

- debug:
    msg: "{{ my_list | length }}"

Example

Suppose my_list is defined as follows:

my_list:
  - item1
  - item2
  - item3

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

- 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.

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