A list of list_obj objects has been created:

[
  {"obj" : "host-01", "join" : "false"},
  {"obj" : "host-02", "join" : "false"}
]

In the task, I select the required object from the list using the selectattr method in the when condition on the object attribute:

- name: Select connection flag
  debug:
    msg: {{ ??? }}
  when: "{{ list_obj | selectattr('obj', 'eq', host_name) }}"

I can't figure out how to output the value of the join attribute of the selected object in msg.

A list of list_obj objects has been created:

[
  {"obj" : "host-01", "join" : "false"},
  {"obj" : "host-02", "join" : "false"}
]

In the task, I select the required object from the list using the selectattr method in the when condition on the object attribute:

- name: Select connection flag
  debug:
    msg: {{ ??? }}
  when: "{{ list_obj | selectattr('obj', 'eq', host_name) }}"

I can't figure out how to output the value of the join attribute of the selected object in msg.

• ansible

2 Answers 2

selectattr is simply a way of filtering a list, it cannot assess if your result is supposed to be a single element of the initial list or not, so, you will still get a list back (or rather an iterator):

jinja-filters.selectattr(value: 't.Iterable[V]', *args: Any, **kwargs: Any) → 't.Iterator[V]'

^{As pointed by the filter signature displayed in Jinja's documentation}

So, you will need to select the first element of your list, either via .0 or [0], or via the first filter.
Then you can select the join attribute.

So,

# Either
msg: "{{ (list_obj | selectattr('obj', 'eq', host_name)).0.join }}"
# Or
msg: "{{ (list_obj | selectattr('obj', 'eq', host_name))[0].join }}"
# Or
msg: "{{ (list_obj | selectattr('obj', 'eq', host_name) | first).join }}"

Given the list for testing

  list_obj:
    - {obj: host_01, join: false}
    - {obj: host_02, join: false}
    - {obj: host_03, join: true}

Convert the list to a dictionary

  dict_obj: "{{ list_obj | items2dict(key_name='obj', value_name='join') }}"

gives

  dict_obj:
    host_01: false
    host_02: false
    host_03: true

Then, the selection is trivial. For example,

    - debug:
        var: dict_obj[inventory_hostname]

- hosts: all

  vars:

    list_obj:
      - {obj: host_01, join: false}
      - {obj: host_02, join: false}
      - {obj: host_03, join: true}

  tasks:

    - name: Create dictionary dict_obj
      run_once: true
      block:

        - set_fact:
            dict_obj: "{{ list_obj | items2dict(key_name='obj', value_name='join') }}"
        - debug:
            var: dict_obj

    - debug:
        var: dict_obj[inventory_hostname]