I’ve just been battling with this one in Ansible so thought I’d post up the solution.

Problem: I want to use the set_fact module to create a list in Ansible. I am currently trying to use the ec2_asg_facts to get a list of instance_ids. The instance_ids are returned as a larger set of results, so I need to loop through the results of the ec2_asg_facts module and grab the instance_ids.

Solution: The following code did the job!

- name: Look up AWS ASG by name
  ec2_asg_facts:
    region: ""
    name: ""
  register: ec2_asg_facts_results

- name: Create list of instance_ids
  set_fact:
    ec2_asg_instance_ids: "{{ ec2_asg_facts_results.results[0].instances | map(attribute='instance_id') | list }}"