Set fact with dynamic key name in ansible

Question

I am trying to shrink several chunks of similar code which looks like:

- ... multiple things is going here
  register: list_register
- name: Generating list
  set_fact: my_list="{{ list_register.results | map(attribute='ansible_facts.list_item') | list }}"

# the same code repeats...

In fact, the only difference between them is that I am using different list names here instead of my_list

In fact I want to do this:

set_fact:
  "{{ some var }}" : "{{ some value }}"

I came across this post but didn't find any answer here.

Is it possible to do so or is there any workaround?

Answer 1

- set_fact: '{{ some_var }}={{ some_value }}'

It creates a string of inline module parameter expression by concatenating value of some_var (fact name), separator = and value of some_value (fact value).

Answer 2

As of 2018, using ansible v2.7.1, the syntax you suggest in your post works perfectly well.

At least in my case, I have this in role "a" :

- name: Set fact
  set_fact: 
     "{{ variable_name }}": "{{ variable_value }}"

And that in role "b" :

- debug:
  msg: "variable_name = {{ variable_name }}"

And execution goes :

TASK [role a : Set fact] *******************************************************
ok: [host_name] => {
  "ansible_facts": {
    "variable_name": "actual value"
  }, 
  "changed": false
}

...

TASK [role b : debug] **********************************************************
ok: [host_name] => {}

MSG:

variable_name = actual value

Answer 3

take a look at this sample playbook:

---
- hosts: localhost
  vars:
    iter:
      - key: abc
        val: xyz
      - key: efg
        val: uvw
  tasks:
    - set_fact: {"{{ item.key }}":"{{ item.val }}"}
      with_items: "{{iter}}"
    - debug: msg="key={{item.key}}, hostvar={{hostvars['localhost'][item.key]}}"
      with_items: "{{iter}}"

Answer 4

The above does not work for me. What finally works is

- set_fact:
    example_dict: "{'{{ some var }}':'{{ some other var }}'}"

Which is in the end obvious. You construct a string (the outer double quotes) which is then interpreted as a hash. In hashes key and value must be single quotes (the inner single quotes around the variable replacements). And finally you just place your variable replacements as in any other string.

Stefan