Call the item variable inside another variable call

Question

I'm trying to loop through a list and append the result to my existing dictionary, but I can't figure out a way to call the 'item' variable inside my set fact.

Although I understand I can't stack moustaches, this is an example of what I'm trying to achieve:

- name: Init list
  set_fact:
    param_list: "{{ param_list | default({ 'full_page_writes': 'off', 'autovacuum': 'off', 'wal_buffers': -1 }) }}"

- name: Append
  set_fact:
# config is a json variable from a previous step
    param_list: "{{ param_list | combine ({ {{ item }} : config.settings.{{ item }}.setting })) }}"
  with_items:
    - work_mem
    - shared_buffers
    - maintenance_work_mem
    - wal_buffers

I tried with lookup, but couldn't find how to use it in this example

=> `"{{ param_list | combine ({ item: config.settings[item].setting }) }}"` — β.εηοιτ.βε, Dec 23 '22 at 20:30
Sorry but your first solution didn't work. As for the link you provided yes it does but what is the syntax in my case. How do I use lookup inside/with combine ? — Mohamed BOUAKKAZ, Dec 23 '22 at 20:51
The expression by `@β.εηοιτ.βε` is correct. Double-check the dictionary *config* — Vladimir Botka, Dec 24 '22 at 00:46

score 1 · Answer 1 · answered Dec 24 '22 at 00:41

^{Put the default dictionary into a variable
params_default_dict:
full_page_writes: 'off'
autovacuum: 'off'
wal_buffers: -1

Then, if the variable param_dict is not defined the task below
- set_fact:
param_dict: "{{ param_dict|default(params_default_dict) }}"

creates the dictionary
param_dict:
autovacuum: 'off'
full_page_writes: 'off'
wal_buffers: -1

Let's put the list of the parameters into a variable as well
params_add:
- work_mem
- shared_buffers
- maintenance_work_mem
- wal_buffers

Create a configuration for testing
config:
settings:
work_mem: v1
shared_buffers: v2
maintenance_work_mem: v3
wal_buffers: v4}

Declare the dictionary of additional parameters

  params_add_dict: "{{ dict(params_add|
                            zip(params_add|
                                map('extract', config.settings))) }}"

gives

  params_add_dict:
    maintenance_work_mem: v3
    shared_buffers: v2
    wal_buffers: v4
    work_mem: v1

Combine the dictionaries

    - set_fact:
        param_dict: "{{ param_dict|combine(params_add_dict) }}"

gives

  param_dict:
    autovacuum: 'off'
    full_page_writes: 'off'
    maintenance_work_mem: v3
    shared_buffers: v2
    wal_buffers: v4
    work_mem: v1

^{Notes

Example of a complete playbook for testing

- hosts: localhost

vars:

params_default_dict:
full_page_writes: 'off'
autovacuum: 'off'
wal_buffers: -1

params_add:
- work_mem
- shared_buffers
- maintenance_work_mem
- wal_buffers

config:
settings:
work_mem: v1
shared_buffers: v2
maintenance_work_mem: v3
wal_buffers: v4

params_add_dict: "{{ dict(params_add|
zip(params_add|
map('extract', config.settings))) }}"

tasks:

- set_fact:
param_dict: "{{ param_dict|default(params_default_dict) }}"
- debug:
var: param_dict

- debug:
var: params_add_dict

- set_fact:
param_dict: "{{ param_dict|combine(params_add_dict) }}"
- debug:
var: param_dict

Test the configuration dictionary with added attribute settings

config:
settings:
work_mem:
settings: v1
shared_buffers:
settings: v2
maintenance_work_mem:
settings: v3
wal_buffers:
settings: v4

The iteration gives the same result
- name: Append
set_fact:
param_dict: "{{ param_dict|
combine({item: config.settings[item].settings}) }}"
loop: "{{ params_add }}"

Change the declaration below to get the result without iteration
params_add_dict: "{{ dict(params_add|
zip(params_add|
map('extract', config.settings, ['settings']))) }}"

Example of a complete playbook for testing
- hosts: localhost

vars:

params_default_dict:
full_page_writes: 'off'
autovacuum: 'off'
wal_buffers: -1

params_add:
- work_mem
- shared_buffers
- maintenance_work_mem
- wal_buffers

config:
settings:
work_mem:
settings: v1
shared_buffers:
settings: v2
maintenance_work_mem:
settings: v3
wal_buffers:
settings: v4

params_add_dict: "{{ dict(params_add|
zip(params_add|
map('extract', config.settings, ['settings']))) }}"

tasks:

- set_fact:
param_dict: "{{ param_dict|default(params_default_dict) }}"
- debug:
var: param_dict

- debug:
var: params_add_dict

- name: Append
set_fact:
param_dict: "{{ param_dict|
combine({item: config.settings[item].settings}) }}"
loop: "{{ params_add }}"
when: iterate|d(false)|bool
- set_fact:
param_dict: "{{ param_dict|combine(params_add_dict) }}"
when: not iterate|d(false)|bool
- debug:
var: param_dict}

Call the item variable inside another variable call

1 Answers1