Ansible loop over list generated with Jinja2 template

Question

I'm using Ansible, and I need to loop over a list stored in a variable I get from a file (with include_vars). Everything is fine, I can use the various values, except I don't manage to loop over the list.

Specifically, I can't do this:

---

- host: localhost
  tasks:
    - debug:
        msg: "{{ item }}"
      loop: "{{ [1,2,3,4] }}"

It yells: "need a list, got: [1,2,3,4]"

but if I use

loop: [1,2,3,4]

Then it works

Can someone explain why it doesn't work?

Extra info: Ansible ver: 2.7.0rc2 Python: 3.9.2

Thanks in advance

Answer 1

Because of the message

need a list, got: [1,2,3,4]

which indicates a variable type mismatch , you may introduce the type_debug filter

- hosts: localhost
  become: no
  gather_facts: no

  vars:

   LIST: [1, 2, 3, 4]

  tasks:

  - name: Show result
    debug:
      msg: "{{ item }} of {{ item | type_debug }}"
    loop: "{{ LIST }}"

and other options for debugging, in example Extended loop variables .

---
- hosts: localhost
  become: no
  gather_facts: no

  tasks:

  - name: Show result
    debug:
      msg: "{{ item | type_debug }}"
    loop: "{{ [1,2,3,4] }}"
    loop_control:
      extended: true
      label: "{{ item }}"

Since this second, your example is working properly in Ansible 2.9.25, resulting into an output of

TASK [Show result] ***********
ok: [localhost] => (item=1) =>
  msg: int
ok: [localhost] => (item=2) =>
  msg: int
ok: [localhost] => (item=3) =>
  msg: int
ok: [localhost] => (item=4) =>
  msg: int

it brings up the question, which version of Ansible you are using?

The issue can be reproduced by

---
- hosts: localhost
  become: no
  gather_facts: no

  tasks:

  - name: Show result
    debug:
      msg: "{{ item | type_debug }}"
    loop: "[1,2,3,4]"

resulting into an output of

TASK [Show result] ***********
fatal: [localhost]: FAILED! =>
  msg: 'Invalid data passed to ''loop'', it requires a list, got this instead: [1,2,3,4]