Filter based on index - Ansible

I would like to know how to extract a string which comes next to 4th occurrence of \\\\\\\\ (4 backslashes), through an Ansible filter.

Input derived from Registering variable

{"ansible_facts": {"dn_var": ["\\\\TEST1\\\\TEST2\\\\TEST 3\\\\TEST 4\\\\TEST 5\\\\TEST 6\\\\TEST 7\\\\TEST 8"]}, "changed": false}

Output expected is Test 4

I've tried to filter using below

- name: to filter
  set_fact:
    team_name: "{{ dn_var.split('\\\\')[3] }}"

but getting this error

The error was: 'list object' has no attribute 'split'

Suggestions would be helpful. Thanks.

Since it is not clear from your question what exactly you are doing and how the input looks like, sometimes it is \\, sometimes it is \\\\, sometime dn_vars is a list with one element and because you haven't provided a Minimal, Reproducible Example, an other approach with Input Data Normalization might work. It is based on the already given answer which should be the accepted answer.

A minimal example playbook

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

  vars:

    dn_vars:
      - "\\TEST1\\TEST2\\TEST 3\\TEST 4\\TEST 5\\TEST 6\\TEST 7\\TEST 8"
      - '\\TEST1\\TEST2\\TEST 3\\TEST 4\\TEST 5\\TEST 6\\TEST 7\\TEST 8'
      - \\\\TEST1\\\\TEST2\\\\TEST 3\\\\TEST 4\\\\TEST 5\\\\TEST 6\\\\TEST 7\\\\TEST 8

    delimiter: '\'
    index: 3

  tasks:

    - debug:
        var: dn_vars

    - name: Data normalization
      debug:
        msg: '{{ item | regex_replace("([\\]+)", "\\") }}'
      loop: "{{ dn_vars }}"
      loop_control:
        extended: true
        label: "{{ ansible_loop.index0 }}"

    - name: Split with Python method
      debug:
        msg: '{{ ((dn_vars | first | regex_replace("([\\]+)", "\\")).split(delimiter) | select)[index] }}'

    - name: Split as of Ansible Core v2.11
      debug:
        msg: '{{ (dn_vars | first | regex_replace("([\\]+)", "\\") | split(delimiter) | select)[index] }}'

will result into an output of

TASK [debug] *********************************************************************
ok: [localhost] =>
  dn_vars:
  - \TEST1\TEST2\TEST 3\TEST 4\TEST 5\TEST 6\TEST 7\TEST 8
  - \\TEST1\\TEST2\\TEST 3\\TEST 4\\TEST 5\\TEST 6\\TEST 7\\TEST 8
  - \\\\TEST1\\\\TEST2\\\\TEST 3\\\\TEST 4\\\\TEST 5\\\\TEST 6\\\\TEST 7\\\\TEST 8

TASK [Data normalization] ***********************************
ok: [localhost] => (item=0) =>
  msg: \TEST1\TEST2\TEST 3\TEST 4\TEST 5\TEST 6\TEST 7\TEST 8
ok: [localhost] => (item=1) =>
  msg: \TEST1\TEST2\TEST 3\TEST 4\TEST 5\TEST 6\TEST 7\TEST 8
ok: [localhost] => (item=2) =>
  msg: \TEST1\TEST2\TEST 3\TEST 4\TEST 5\TEST 6\TEST 7\TEST 8

TASK [Split with Python method] *****************************
ok: [localhost] =>
  msg: TEST 4

TASK [Split as of Ansible Core v2.11] ***********************
ok: [localhost] =>
  msg: TEST 4

It will work any input list element, like dn_vars | last ... or (dn_vars)[1].