How convert a list into list of object in ansible

Question

In my playbook I have a list like this

users:
  - readonly
  - write

and I need to translate it to a list of objects/dictionaries

userDict:
  - {'username': readonly, 'database': admin}
  - {'username': write, 'database': admin}

I know, I can do it with Jinja templates:

userDict: |
  {% set ret = [] %}
  {% for item in users %}
  {%   set _ = ret.append({'username': item, 'database': 'admin'}) %}
  {% endfor %}
  {{ ret }}

But I am looking for a shorter solution with filter, something like this:

userDict: "{{ users | map('map', 'username') | combine({'database': admin}) }}"

U880D · Accepted Answer · 2025-05-05 06:49:08Z

There are acutally two questions

How to create a list of dicts from a list
How to add an element to a list of dicts

A minimal example could look like

---
- hosts: localhost
  become: false
  gather_facts: false

  vars:

    users:
      - readonly
      - write

  tasks:

    - debug:
        msg: |
          {% set ret = [] %}
          {% for item in users %}
          {%   set _ = ret.append({'username': item, 'database': 'admin'}) %}
          {% endfor %}
          {{ ret }}

    - name: Create a new list
      debug:
        msg: "{{ item | combine( {'database': 'admin'} ) }}"
      loop: "{{ users | map('community.general.dict_kv', 'username') }}"
      loop_control:
        extended: true
        label: "{{ ansible_loop.index }}"

resulting into an output of

TASK [debug] *****************
ok: [localhost] =>
  msg:
  - database: admin
    username: readonly
  - database: admin
    username: write

TASK [Create a new list] *****
ok: [localhost] => (item=1) =>
  msg:
    database: admin
    username: readonly
ok: [localhost] => (item=2) =>
  msg:
    database: admin
    username: write

So finally one may end up with

    - name: Create a new list
      debug:
        msg: "{{ users | map('community.general.dict_kv', 'username') | map('combine', db_entry) }}"
      vars:
        db_entry: {'database': 'admin'}

Vladimir Botka · Accepted Answer · 2025-05-05 07:51:27Z

Given the lists

user: [readonly, write]
db: [admin]

Create the dictionary

user_dict: "{{ dict(user | product(db)) }}"

gives

user_dict:
    readonly: admin
    write: admin

Then use the dictionary to create the list

user_list: "{{ user_dict | dict2items(key_name='username',
                                      value_name='database') }}"

gives what you want

user_list:
    - {database: admin, username: readonly}
    - {database: admin, username: write}

Example of a complete playbook for testing

- hosts: localhost

  vars:

    user: [readonly, write]
    db: [admin]
    user_dict: "{{ dict(user | product(db)) }}" 
    user_list: "{{ user_dict | dict2items(key_name='username',
                                          value_name='database') }}"

  tasks:

    - debug:
        var: user_dict
    - debug:
        var: user_list | to_yaml

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