Building up a dictionary/hash with lists - ansible

Question

I am attempting to build a dictionary but cannot grasp how jinja2 interpolates variables.
I want to set a specific item in the array (for example item[0]) to a specific key-value dictionary item.
- set_fact:
nodes:
- node1
- node2
- set_fact:
list_one:
- f-one
- f-two
- set_fact:
list_two:
- n-one
- n-two
what I want:
- set_fact:
**node_dict:
node1:
labels:
f-one: n-one
node2:
labels:
f-two: n-two**
When I run :
- name: check loop1
debug:
msg: '{{item[0]}} - {{item[1]}} - {{ item[2]}} '
with_nested:
- '{{ nodes }}'
- '{{ list_one }}'
- '{{ list_two }}'
item variable is availble. But doing this:
- set_fact:
final:
'{{item[0]}}':
labels:
"{{item[1] }}" : "{{item[2]}}"
with_nested:
- '{{ nodes }}'
- '{{ list_one }}'
- '{{ list_two }}'
results in an error.
Can someone explain why? How do I end up with my desired result?

Answer 1

Although your last piece of code above does not meet your requirement, It's perfectly valid: I'm not getting any error when running it.
As your are using it right now, set_fact is overwriting your final variable on each loop. To append element to a dict like your are trying to do, you need to initialize the var to an empty dict and combine it with the values you are calculating for each iteration. Since your calculated values are a dict themselves, you will need to use recursive=True if you have to write expressions deep inside the dict.
If I take into account your original data and your expected result, you want to relate the Nth element of each lists together. This is not what nested does (loop over nodes with a sub-loop on list_one sub-sub-loop on list_two....). In your case, you simply need to loop over an index of the length of your lists and combine the elements of same index together. My take below.
---
- name: test for SO
hosts: localhost
vars:
nodes:
- node1
- node2
list_one:
- f-one
- f-two
list_two:
- n-one
- n-two
tasks:
- name: Make my config
set_fact:
final: >-
{{
final
| default({})
| combine ({
nodes[item]: {
'labels': {
list_one[item]: list_two[item]
}
}
}, recursive=True)
}}
loop: "{{ range(nodes | length) | list }}"
- name: debug
debug:
var: final
which gives the following result
$ ansible-playbook test.yml
PLAY [test for SO] ******************************************************************
TASK [Gathering Facts] **************************************************************
ok: [localhost]
TASK [Make my config] ***************************************************************
ok: [localhost] => (item=0)
ok: [localhost] => (item=1)
TASK [debug] ************************************************************************
ok: [localhost] => {
"final": {
"node1": {
"labels": {
"f-one": "n-one"
}
},
"node2": {
"labels": {
"f-two": "n-two"
}
}
}
}
PLAY RECAP **************************************************************************
localhost : ok=3 changed=0 unreachable=0 failed=0
Edit: The same result can be acheived using the zip filter (which I (re)discovered today reading an other contribution).
- name: Make my config
set_fact:
final: >-
{{
final
| default({})
| combine ({
item.0: {
'labels': {
item.1: item.2
}
}
}, recursive=True)
}}
loop: "{{ nodes | zip(list_one, list_two) | list }}"

Answer 2

An option would be to create the list of labels and then combine the dictionary. The play below
- hosts: localhost
vars:
nodes:
- node1
- node2
list_one:
- f-one
- f-two
list_two:
- n-one
- n-two
node_dict: {}
my_labels: []
tasks:
- set_fact:
my_labels: "{{ my_labels + [ {list_one[my_idx]:list_two[my_idx]} ] }}"
loop: "{{ nodes }}"
loop_control:
index_var: my_idx
- set_fact:
node_dict: "{{ node_dict | combine({item:{'labels':my_labels[my_idx]}}) }}"
loop: "{{ nodes }}"
loop_control:
index_var: my_idx
- debug:
var: node_dict
gives:
"node_dict": {
"node1": {
"labels": {
"f-one": "n-one"
}
},
"node2": {
"labels": {
"f-two": "n-two"
}
}
}