How to get the particular index value of a combined list for a desired position ansible

Question

I am learning ansible and tried to test how ansible zip works well with loop in order to get the appropriate index value of the combined list in ansible.

$ cat   test2_zip_list.yml
---
- name: testing zip with list
  hosts: localhost
  vars:
    nums:
      - 1
      - 2
      - 3
    strs:
      - a
      - b
      - c

  tasks:
  - set_fact:
      num: "{{ item }}"
    loop: "{{ nums | zip(strs) | list }}"

  - name: numa
    debug:
     msg: "{{ num }}"

Output:

Below is the combined list output which is as expected..

$ ansible-playbook  test2_zip_list.yml -vvv
--- skipped some portion ----- 
PLAYBOOK: test2_zip_list.yml *************************************************************************************************************************************************************
1 plays in test2_zip_list.yml

PLAY [testing zip with list] *************************************************************************************************************************************************************
META: ran handlers

TASK [set_fact] **************************************************************************************************************************************************************************
task path: /home/user1/ansible_work/test2_zip_list.yml:15
ok: [localhost] => (item=[1, u'a']) => {
    "ansible_facts": {
        "num": [
            1,
            "a"
        ]
    },
    "ansible_loop_var": "item",
    "changed": false,
    "item": [
        1,
        "a"
    ]
}
ok: [localhost] => (item=[2, u'b']) => {
    "ansible_facts": {
        "num": [
            2,
            "b"
        ]
    },
    "ansible_loop_var": "item",
    "changed": false,
    "item": [
        2,
        "b"
    ]
}
ok: [localhost] => (item=[3, u'c']) => {
    "ansible_facts": {
        "num": [
            3,
            "c"
        ]
    },
    "ansible_loop_var": "item",
    "changed": false,
    "item": [
        3,
        "c"
    ]
}

TASK [numa] ******************************************************************************************************************************************************************************
task path: /home/user1/ansible_work/test2_zip_list.yml:19
ok: [localhost] => {
    "msg": [
        3,
        "c"
    ]
}
META: ran handlers
META: ran handlers

PLAY RECAP *******************************************************************************************************************************************************************************
localhost                  : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Other way

if i want to change my play and want to certain value of certain index position..

$ cat  test2_zip_list.yml
---
- name: testing zip with list
  hosts: localhost
  vars:
    nums:
      - 1
      - 2
      - 3
    strs:
      - a
      - b
      - c

  tasks:
  - set_fact:
      num: "{{ item.1 }}"   <-- this is what i given to test 
    loop: "{{ nums | zip(strs) | list }}"

  - name: numa
    debug:
     msg: "{{ num }}"

What i got is below ..

$ ansible-playbook  test2_zip_list.yml
PLAY [testing zip with list] *************************************************************************************************************************************************************

TASK [set_fact] **************************************************************************************************************************************************************************
ok: [localhost] => (item=[1, u'a'])
ok: [localhost] => (item=[2, u'b'])
ok: [localhost] => (item=[3, u'c'])

TASK [numa] ******************************************************************************************************************************************************************************
ok: [localhost] => {
    "msg": "c"
}

PLAY RECAP *******************************************************************************************************************************************************************************
localhost                  : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

So, if you will see its picked the first index of the combined value of list of the last combine ie item=[3, u'c'] , So, i'm looking in case i need to get the first index of (item=[2, u'b']) then how to get that.

Answer 1

the issue with your set_fact task is that it iterates of the elements of nums | zip(strs) | list and sets the num to the element each time. you need to use a condition to do the value assignment only when the iteration has first element = 2.

here is a way to do it:

  tasks:
  - set_fact:
      my_desired_list: "{{ item }}"
    when: item.0 == 2 or 
    loop: "{{ nums | zip(strs) | list }}"

  - name: numa
    debug:
     var: my_desired_list

if you want to add a condition for 2nd element to be equal to b then:

  tasks:
  - set_fact:
      my_desired_list: "{{ item }}"
    when: item.0 == 2 or item.1 == "b"
    loop: "{{ nums | zip(strs) | list }}"

  - name: numa
    debug:
     var: my_desired_list

(or can be and depending or your needs)